drivers/mtd/nand/qcom_nandc.c

/*
 * Copyright (c) 2016, The Linux Foundation. All rights reserved.
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/clk.h>
#include <linux/slab.h>
#include <linux/bitops.h>
#include <linux/dma-mapping.h>
#include <linux/dmaengine.h>
#include <linux/module.h>
#include <linux/mtd/nand.h>
#include <linux/mtd/partitions.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/delay.h>

/* NANDc reg offsets */
#define	NAND_FLASH_CMD			0x00
#define	NAND_ADDR0			0x04
#define	NAND_ADDR1			0x08
#define	NAND_FLASH_CHIP_SELECT		0x0c
#define	NAND_EXEC_CMD			0x10
#define	NAND_FLASH_STATUS		0x14
#define	NAND_BUFFER_STATUS		0x18
#define	NAND_DEV0_CFG0			0x20
#define	NAND_DEV0_CFG1			0x24
#define	NAND_DEV0_ECC_CFG		0x28
#define	NAND_DEV1_ECC_CFG		0x2c
#define	NAND_DEV1_CFG0			0x30
#define	NAND_DEV1_CFG1			0x34
#define	NAND_READ_ID			0x40
#define	NAND_READ_STATUS		0x44
#define	NAND_DEV_CMD0			0xa0
#define	NAND_DEV_CMD1			0xa4
#define	NAND_DEV_CMD2			0xa8
#define	NAND_DEV_CMD_VLD		0xac
#define	SFLASHC_BURST_CFG		0xe0
#define	NAND_ERASED_CW_DETECT_CFG	0xe8
#define	NAND_ERASED_CW_DETECT_STATUS	0xec
#define	NAND_EBI2_ECC_BUF_CFG		0xf0
#define	FLASH_BUF_ACC			0x100

#define	NAND_CTRL			0xf00
#define	NAND_VERSION			0xf08
#define	NAND_READ_LOCATION_0		0xf20
#define	NAND_READ_LOCATION_1		0xf24
#define	NAND_READ_LOCATION_2		0xf28
#define	NAND_READ_LOCATION_3		0xf2c

/* dummy register offsets, used by write_reg_dma */
#define	NAND_DEV_CMD1_RESTORE		0xdead
#define	NAND_DEV_CMD_VLD_RESTORE	0xbeef

/* NAND_FLASH_CMD bits */
#define	PAGE_ACC			BIT(4)
#define	LAST_PAGE			BIT(5)

/* NAND_FLASH_CHIP_SELECT bits */
#define	NAND_DEV_SEL			0
#define	DM_EN				BIT(2)

/* NAND_FLASH_STATUS bits */
#define	FS_OP_ERR			BIT(4)
#define	FS_READY_BSY_N			BIT(5)
#define	FS_MPU_ERR			BIT(8)
#define	FS_DEVICE_STS_ERR		BIT(16)
#define	FS_DEVICE_WP			BIT(23)

/* NAND_BUFFER_STATUS bits */
#define	BS_UNCORRECTABLE_BIT		BIT(8)
#define	BS_CORRECTABLE_ERR_MSK		0x1f

/* NAND_DEVn_CFG0 bits */
#define	DISABLE_STATUS_AFTER_WRITE	4
#define	CW_PER_PAGE			6
#define	UD_SIZE_BYTES			9
#define	ECC_PARITY_SIZE_BYTES_RS	19
#define	SPARE_SIZE_BYTES		23
#define	NUM_ADDR_CYCLES			27
#define	STATUS_BFR_READ			30
#define	SET_RD_MODE_AFTER_STATUS	31

/* NAND_DEVn_CFG0 bits */
#define	DEV0_CFG1_ECC_DISABLE		0
#define	WIDE_FLASH			1
#define	NAND_RECOVERY_CYCLES		2
#define	CS_ACTIVE_BSY			5
#define	BAD_BLOCK_BYTE_NUM		6
#define	BAD_BLOCK_IN_SPARE_AREA		16
#define	WR_RD_BSY_GAP			17
#define	ENABLE_BCH_ECC			27

/* NAND_DEV0_ECC_CFG bits */
#define	ECC_CFG_ECC_DISABLE		0
#define	ECC_SW_RESET			1
#define	ECC_MODE			4
#define	ECC_PARITY_SIZE_BYTES_BCH	8
#define	ECC_NUM_DATA_BYTES		16
#define	ECC_FORCE_CLK_OPEN		30

/* NAND_DEV_CMD1 bits */
#define	READ_ADDR			0

/* NAND_DEV_CMD_VLD bits */
#define	READ_START_VLD			BIT(0)
#define	READ_STOP_VLD			BIT(1)
#define	WRITE_START_VLD			BIT(2)
#define	ERASE_START_VLD			BIT(3)
#define	SEQ_READ_START_VLD		BIT(4)

/* NAND_EBI2_ECC_BUF_CFG bits */
#define	NUM_STEPS			0

/* NAND_ERASED_CW_DETECT_CFG bits */
#define	ERASED_CW_ECC_MASK		1
#define	AUTO_DETECT_RES			0
#define	MASK_ECC			(1 << ERASED_CW_ECC_MASK)
#define	RESET_ERASED_DET		(1 << AUTO_DETECT_RES)
#define	ACTIVE_ERASED_DET		(0 << AUTO_DETECT_RES)
#define	CLR_ERASED_PAGE_DET		(RESET_ERASED_DET | MASK_ECC)
#define	SET_ERASED_PAGE_DET		(ACTIVE_ERASED_DET | MASK_ECC)

/* NAND_ERASED_CW_DETECT_STATUS bits */
#define	PAGE_ALL_ERASED			BIT(7)
#define	CODEWORD_ALL_ERASED		BIT(6)
#define	PAGE_ERASED			BIT(5)
#define	CODEWORD_ERASED			BIT(4)
#define	ERASED_PAGE			(PAGE_ALL_ERASED | PAGE_ERASED)
#define	ERASED_CW			(CODEWORD_ALL_ERASED | CODEWORD_ERASED)

/* NAND_READ_LOCATION_n bits */
#define READ_LOCATION_OFFSET		0
#define READ_LOCATION_SIZE		16
#define READ_LOCATION_LAST		31

/* Version Mask */
#define	NAND_VERSION_MAJOR_MASK		0xf0000000
#define	NAND_VERSION_MAJOR_SHIFT	28
#define	NAND_VERSION_MINOR_MASK		0x0fff0000
#define	NAND_VERSION_MINOR_SHIFT	16

/* NAND OP_CMDs */
#define	PAGE_READ			0x2
#define	PAGE_READ_WITH_ECC		0x3
#define	PAGE_READ_WITH_ECC_SPARE	0x4
#define	PROGRAM_PAGE			0x6
#define	PAGE_PROGRAM_WITH_ECC		0x7
#define	PROGRAM_PAGE_SPARE		0x9
#define	BLOCK_ERASE			0xa
#define	FETCH_ID			0xb
#define	RESET_DEVICE			0xd

/* Default Value for NAND_DEV_CMD_VLD */
#define NAND_DEV_CMD_VLD_VAL		(READ_START_VLD | WRITE_START_VLD | \
					 ERASE_START_VLD | SEQ_READ_START_VLD)

/* NAND_CTRL bits */
#define	BAM_MODE_EN			BIT(0)

/*
 * the NAND controller performs reads/writes with ECC in 516 byte chunks.
 * the driver calls the chunks 'step' or 'codeword' interchangeably
 */
#define	NANDC_STEP_SIZE			512

/*
 * the largest page size we support is 8K, this will have 16 steps/codewords
 * of 512 bytes each
 */
#define	MAX_NUM_STEPS			(SZ_8K / NANDC_STEP_SIZE)

/* we read at most 3 registers per codeword scan */
#define	MAX_REG_RD			(3 * MAX_NUM_STEPS)

/* ECC modes supported by the controller */
#define	ECC_NONE	BIT(0)
#define	ECC_RS_4BIT	BIT(1)
#define	ECC_BCH_4BIT	BIT(2)
#define	ECC_BCH_8BIT	BIT(3)

#define nandc_set_read_loc(nandc, reg, offset, size, is_last)	\
nandc_set_reg(nandc, NAND_READ_LOCATION_##reg,			\
	      ((offset) << READ_LOCATION_OFFSET) |		\
	      ((size) << READ_LOCATION_SIZE) |			\
	      ((is_last) << READ_LOCATION_LAST))

#define QPIC_PER_CW_CMD_SGL		32
#define QPIC_PER_CW_DATA_SGL		8

/*
 * Flags used in DMA descriptor preparation helper functions
 * (i.e. read_reg_dma/write_reg_dma/read_data_dma/write_data_dma)
 */
/* Don't set the EOT in current tx BAM sgl */
#define NAND_BAM_NO_EOT			BIT(0)
/* Set the NWD flag in current BAM sgl */
#define NAND_BAM_NWD			BIT(1)
/* Finish writing in the current BAM sgl and start writing in another BAM sgl */
#define NAND_BAM_NEXT_SGL		BIT(2)
/*
 * Erased codeword status is being used two times in single transfer so this
 * flag will determine the current value of erased codeword status register
 */
#define NAND_ERASED_CW_SET		BIT(4)

/*
 * This data type corresponds to the BAM transaction which will be used for all
 * NAND transfers.
 * @cmd_sgl - sgl for NAND BAM command pipe
 * @data_sgl - sgl for NAND BAM consumer/producer pipe
 * @cmd_sgl_pos - current index in command sgl.
 * @cmd_sgl_start - start index in command sgl.
 * @tx_sgl_pos - current index in data sgl for tx.
 * @tx_sgl_start - start index in data sgl for tx.
 * @rx_sgl_pos - current index in data sgl for rx.
 * @rx_sgl_start - start index in data sgl for rx.
 */
struct bam_transaction {
	struct scatterlist *cmd_sgl;
	struct scatterlist *data_sgl;
	u32 cmd_sgl_pos;
	u32 cmd_sgl_start;
	u32 tx_sgl_pos;
	u32 tx_sgl_start;
	u32 rx_sgl_pos;
	u32 rx_sgl_start;
};

/*
 * This data type corresponds to the nand dma descriptor
 * @list - list for desc_info
 * @dir - DMA transfer direction
 * @adm_sgl - sgl which will be used for single sgl dma descriptor. Only used by
 *	      ADM
 * @bam_sgl - sgl which will be used for dma descriptor. Only used by BAM
 * @sgl_cnt - number of SGL in bam_sgl. Only used by BAM
 * @dma_desc - low level DMA engine descriptor
 */
struct desc_info {
	struct list_head node;

	enum dma_data_direction dir;
	union {
		struct scatterlist adm_sgl;
		struct {
			struct scatterlist *bam_sgl;
			int sgl_cnt;
		};
	};
	struct dma_async_tx_descriptor *dma_desc;
};

/*
 * holds the current register values that we want to write. acts as a contiguous
 * chunk of memory which we use to write the controller registers through DMA.
 */
struct nandc_regs {
	__le32 cmd;
	__le32 addr0;
	__le32 addr1;
	__le32 chip_sel;
	__le32 exec;

	__le32 cfg0;
	__le32 cfg1;
	__le32 ecc_bch_cfg;

	__le32 clrflashstatus;
	__le32 clrreadstatus;

	__le32 cmd1;
	__le32 vld;

	__le32 orig_cmd1;
	__le32 orig_vld;

	__le32 ecc_buf_cfg;
	__le32 read_location0;
	__le32 read_location1;
	__le32 read_location2;
	__le32 read_location3;

	__le32 erased_cw_detect_cfg_clr;
	__le32 erased_cw_detect_cfg_set;
};

/*
 * NAND controller data struct
 *
 * @controller:			base controller structure
 * @host_list:			list containing all the chips attached to the
 *				controller
 * @dev:			parent device
 * @base:			MMIO base
 * @base_dma:			physical base address of controller registers
 * @core_clk:			controller clock
 * @aon_clk:			another controller clock
 *
 * @chan:			dma channel
 * @cmd_crci:			ADM DMA CRCI for command flow control
 * @data_crci:			ADM DMA CRCI for data flow control
 * @desc_list:			DMA descriptor list (list of desc_infos)
 *
 * @data_buffer:		our local DMA buffer for page read/writes,
 *				used when we can't use the buffer provided
 *				by upper layers directly
 * @buf_size/count/start:	markers for chip->read_buf/write_buf functions
 * @reg_read_buf:		local buffer for reading back registers via DMA
 * @reg_read_dma:		contains dma address for register read buffer
 * @reg_read_pos:		marker for data read in reg_read_buf
 *
 * @regs:			a contiguous chunk of memory for DMA register
 *				writes. contains the register values to be
 *				written to controller
 * @cmd1/vld:			some fixed controller register values
 * @props:			properties of current NAND controller,
 *				initialized via DT match data
 * @max_cwperpage:		maximum QPIC codewords required. calculated
 *				from all connected NAND devices pagesize
 */
struct qcom_nand_controller {
	struct nand_hw_control controller;
	struct list_head host_list;

	struct device *dev;

	void __iomem *base;
	dma_addr_t base_dma;

	struct clk *core_clk;
	struct clk *aon_clk;

	union {
		/* will be used only by QPIC for BAM DMA */
		struct {
			struct dma_chan *tx_chan;
			struct dma_chan *rx_chan;
			struct dma_chan *cmd_chan;
		};

		/* will be used only by EBI2 for ADM DMA */
		struct {
			struct dma_chan *chan;
			unsigned int cmd_crci;
			unsigned int data_crci;
		};
	};

	struct list_head desc_list;
	struct bam_transaction *bam_txn;

	u8		*data_buffer;
	int		buf_size;
	int		buf_count;
	int		buf_start;
	unsigned int	max_cwperpage;

	__le32 *reg_read_buf;
	dma_addr_t reg_read_dma;
	int reg_read_pos;

	struct nandc_regs *regs;

	u32 cmd1, vld;
	const struct qcom_nandc_props *props;
};

/*
 * NAND chip structure
 *
 * @chip:			base NAND chip structure
 * @node:			list node to add itself to host_list in
 *				qcom_nand_controller
 *
 * @cs:				chip select value for this chip
 * @cw_size:			the number of bytes in a single step/codeword
 *				of a page, consisting of all data, ecc, spare
 *				and reserved bytes
 * @cw_data:			the number of bytes within a codeword protected
 *				by ECC
 * @use_ecc:			request the controller to use ECC for the
 *				upcoming read/write
 * @bch_enabled:		flag to tell whether BCH ECC mode is used
 * @ecc_bytes_hw:		ECC bytes used by controller hardware for this
 *				chip
 * @status:			value to be returned if NAND_CMD_STATUS command
 *				is executed
 * @last_command:		keeps track of last command on this chip. used
 *				for reading correct status
 *
 * @cfg0, cfg1, cfg0_raw..:	NANDc register configurations needed for
 *				ecc/non-ecc mode for the current nand flash
 *				device
 */
struct qcom_nand_host {
	struct nand_chip chip;
	struct list_head node;

	int cs;
	int cw_size;
	int cw_data;
	bool use_ecc;
	bool bch_enabled;
	int ecc_bytes_hw;
	int spare_bytes;
	int bbm_size;
	u8 status;
	int last_command;

	u32 cfg0, cfg1;
	u32 cfg0_raw, cfg1_raw;
	u32 ecc_buf_cfg;
	u32 ecc_bch_cfg;
	u32 clrflashstatus;
	u32 clrreadstatus;
};

/*
 * This data type corresponds to the NAND controller properties which varies
 * among different NAND controllers.
 * @ecc_modes - ecc mode for NAND
 * @is_bam - whether NAND controller is using BAM
 */
struct qcom_nandc_props {
	u32 ecc_modes;
	bool is_bam;
};

/* Frees the BAM transaction memory */
static void free_bam_transaction(struct qcom_nand_controller *nandc)
{
	struct bam_transaction *bam_txn = nandc->bam_txn;

	devm_kfree(nandc->dev, bam_txn);
}

/* Allocates and Initializes the BAM transaction */
static struct bam_transaction *
alloc_bam_transaction(struct qcom_nand_controller *nandc)
{
	struct bam_transaction *bam_txn;
	size_t bam_txn_size;
	unsigned int num_cw = nandc->max_cwperpage;
	void *bam_txn_buf;

	bam_txn_size =
		sizeof(*bam_txn) + num_cw *
		((sizeof(*bam_txn->cmd_sgl) * QPIC_PER_CW_CMD_SGL) +
		(sizeof(*bam_txn->data_sgl) * QPIC_PER_CW_DATA_SGL));

	bam_txn_buf = devm_kzalloc(nandc->dev, bam_txn_size, GFP_KERNEL);
	if (!bam_txn_buf)
		return NULL;

	bam_txn = bam_txn_buf;
	bam_txn_buf += sizeof(*bam_txn);

	bam_txn->cmd_sgl = bam_txn_buf;
	bam_txn_buf +=
		sizeof(*bam_txn->cmd_sgl) * QPIC_PER_CW_CMD_SGL * num_cw;

	bam_txn->data_sgl = bam_txn_buf;

	return bam_txn;
}

/* Clears the BAM transaction indexes */
static void clear_bam_transaction(struct qcom_nand_controller *nandc)
{
	struct bam_transaction *bam_txn = nandc->bam_txn;

	if (!nandc->props->is_bam)
		return;

	bam_txn->cmd_sgl_pos = 0;
	bam_txn->cmd_sgl_start = 0;
	bam_txn->tx_sgl_pos = 0;
	bam_txn->tx_sgl_start = 0;
	bam_txn->rx_sgl_pos = 0;
	bam_txn->rx_sgl_start = 0;

	sg_init_table(bam_txn->cmd_sgl, nandc->max_cwperpage *
		      QPIC_PER_CW_CMD_SGL);
	sg_init_table(bam_txn->data_sgl, nandc->max_cwperpage *
		      QPIC_PER_CW_DATA_SGL);
}

static inline struct qcom_nand_host *to_qcom_nand_host(struct nand_chip *chip)
{
	return container_of(chip, struct qcom_nand_host, chip);
}

static inline struct qcom_nand_controller *
get_qcom_nand_controller(struct nand_chip *chip)
{
	return container_of(chip->controller, struct qcom_nand_controller,
			    controller);
}

static inline u32 nandc_read(struct qcom_nand_controller *nandc, int offset)
{
	return ioread32(nandc->base + offset);
}

static inline void nandc_write(struct qcom_nand_controller *nandc, int offset,
			       u32 val)
{
	iowrite32(val, nandc->base + offset);
}

static inline void nandc_read_buffer_sync(struct qcom_nand_controller *nandc,
					  bool is_cpu)
{
	if (!nandc->props->is_bam)
		return;

	if (is_cpu)
		dma_sync_single_for_cpu(nandc->dev, nandc->reg_read_dma,
					MAX_REG_RD *
					sizeof(*nandc->reg_read_buf),
					DMA_FROM_DEVICE);
	else
		dma_sync_single_for_device(nandc->dev, nandc->reg_read_dma,
					   MAX_REG_RD *
					   sizeof(*nandc->reg_read_buf),
					   DMA_FROM_DEVICE);
}

static __le32 *offset_to_nandc_reg(struct nandc_regs *regs, int offset)
{
	switch (offset) {
	case NAND_FLASH_CMD:
		return &regs->cmd;
	case NAND_ADDR0:
		return &regs->addr0;
	case NAND_ADDR1:
		return &regs->addr1;
	case NAND_FLASH_CHIP_SELECT:
		return &regs->chip_sel;
	case NAND_EXEC_CMD:
		return &regs->exec;
	case NAND_FLASH_STATUS:
		return &regs->clrflashstatus;
	case NAND_DEV0_CFG0:
		return &regs->cfg0;
	case NAND_DEV0_CFG1:
		return &regs->cfg1;
	case NAND_DEV0_ECC_CFG:
		return &regs->ecc_bch_cfg;
	case NAND_READ_STATUS:
		return &regs->clrreadstatus;
	case NAND_DEV_CMD1:
		return &regs->cmd1;
	case NAND_DEV_CMD1_RESTORE:
		return &regs->orig_cmd1;
	case NAND_DEV_CMD_VLD:
		return &regs->vld;
	case NAND_DEV_CMD_VLD_RESTORE:
		return &regs->orig_vld;
	case NAND_EBI2_ECC_BUF_CFG:
		return &regs->ecc_buf_cfg;
	case NAND_READ_LOCATION_0:
		return &regs->read_location0;
	case NAND_READ_LOCATION_1:
		return &regs->read_location1;
	case NAND_READ_LOCATION_2:
		return &regs->read_location2;
	case NAND_READ_LOCATION_3:
		return &regs->read_location3;
	default:
		return NULL;
	}
}

static void nandc_set_reg(struct qcom_nand_controller *nandc, int offset,
			  u32 val)
{
	struct nandc_regs *regs = nandc->regs;
	__le32 *reg;

	reg = offset_to_nandc_reg(regs, offset);

	if (reg)
		*reg = cpu_to_le32(val);
}

/* helper to configure address register values */
static void set_address(struct qcom_nand_host *host, u16 column, int page)
{
	struct nand_chip *chip = &host->chip;
	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);

	if (chip->options & NAND_BUSWIDTH_16)
		column >>= 1;

	nandc_set_reg(nandc, NAND_ADDR0, page << 16 | column);
	nandc_set_reg(nandc, NAND_ADDR1, page >> 16 & 0xff);
}

/*
 * update_rw_regs:	set up read/write register values, these will be
 *			written to the NAND controller registers via DMA
 *
 * @num_cw:		number of steps for the read/write operation
 * @read:		read or write operation
 */
static void update_rw_regs(struct qcom_nand_host *host, int num_cw, bool read)
{
	struct nand_chip *chip = &host->chip;
	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);
	u32 cmd, cfg0, cfg1, ecc_bch_cfg;

	if (read) {
		if (host->use_ecc)
			cmd = PAGE_READ_WITH_ECC | PAGE_ACC | LAST_PAGE;
		else
			cmd = PAGE_READ | PAGE_ACC | LAST_PAGE;
	} else {
			cmd = PROGRAM_PAGE | PAGE_ACC | LAST_PAGE;
	}

	if (host->use_ecc) {
		cfg0 = (host->cfg0 & ~(7U << CW_PER_PAGE)) |
				(num_cw - 1) << CW_PER_PAGE;

		cfg1 = host->cfg1;
		ecc_bch_cfg = host->ecc_bch_cfg;
	} else {
		cfg0 = (host->cfg0_raw & ~(7U << CW_PER_PAGE)) |
				(num_cw - 1) << CW_PER_PAGE;

		cfg1 = host->cfg1_raw;
		ecc_bch_cfg = 1 << ECC_CFG_ECC_DISABLE;
	}

	nandc_set_reg(nandc, NAND_FLASH_CMD, cmd);
	nandc_set_reg(nandc, NAND_DEV0_CFG0, cfg0);
	nandc_set_reg(nandc, NAND_DEV0_CFG1, cfg1);
	nandc_set_reg(nandc, NAND_DEV0_ECC_CFG, ecc_bch_cfg);
	nandc_set_reg(nandc, NAND_EBI2_ECC_BUF_CFG, host->ecc_buf_cfg);
	nandc_set_reg(nandc, NAND_FLASH_STATUS, host->clrflashstatus);
	nandc_set_reg(nandc, NAND_READ_STATUS, host->clrreadstatus);
	nandc_set_reg(nandc, NAND_EXEC_CMD, 1);

	if (read)
		nandc_set_read_loc(nandc, 0, 0, host->use_ecc ?
				   host->cw_data : host->cw_size, 1);
}

/*
 * Maps the scatter gather list for DMA transfer and forms the DMA descriptor
 * for BAM. This descriptor will be added in the NAND DMA descriptor queue
 * which will be submitted to DMA engine.
 */
static int prepare_bam_async_desc(struct qcom_nand_controller *nandc,
				  struct dma_chan *chan,
				  unsigned long flags)
{
	struct desc_info *desc;
	struct scatterlist *sgl;
	unsigned int sgl_cnt;
	int ret;
	struct bam_transaction *bam_txn = nandc->bam_txn;
	enum dma_transfer_direction dir_eng;
	struct dma_async_tx_descriptor *dma_desc;

	desc = kzalloc(sizeof(*desc), GFP_KERNEL);
	if (!desc)
		return -ENOMEM;

	if (chan == nandc->cmd_chan) {
		sgl = &bam_txn->cmd_sgl[bam_txn->cmd_sgl_start];
		sgl_cnt = bam_txn->cmd_sgl_pos - bam_txn->cmd_sgl_start;
		bam_txn->cmd_sgl_start = bam_txn->cmd_sgl_pos;
		dir_eng = DMA_MEM_TO_DEV;
		desc->dir = DMA_TO_DEVICE;
	} else if (chan == nandc->tx_chan) {
		sgl = &bam_txn->data_sgl[bam_txn->tx_sgl_start];
		sgl_cnt = bam_txn->tx_sgl_pos - bam_txn->tx_sgl_start;
		bam_txn->tx_sgl_start = bam_txn->tx_sgl_pos;
		dir_eng = DMA_MEM_TO_DEV;
		desc->dir = DMA_TO_DEVICE;
	} else {
		sgl = &bam_txn->data_sgl[bam_txn->rx_sgl_start];
		sgl_cnt = bam_txn->rx_sgl_pos - bam_txn->rx_sgl_start;
		bam_txn->rx_sgl_start = bam_txn->rx_sgl_pos;
		dir_eng = DMA_DEV_TO_MEM;
		desc->dir = DMA_FROM_DEVICE;
	}

	sg_mark_end(sgl + sgl_cnt - 1);
	ret = dma_map_sg(nandc->dev, sgl, sgl_cnt, desc->dir);
	if (ret == 0) {
		dev_err(nandc->dev, "failure in mapping desc\n");
		kfree(desc);
		return -ENOMEM;
	}

	desc->sgl_cnt = sgl_cnt;
	desc->bam_sgl = sgl;

	dma_desc = dmaengine_prep_slave_sg(chan, sgl, sgl_cnt, dir_eng,
					   flags);

	if (!dma_desc) {
		dev_err(nandc->dev, "failure in prep desc\n");
		dma_unmap_sg(nandc->dev, sgl, sgl_cnt, desc->dir);
		kfree(desc);
		return -EINVAL;
	}

	desc->dma_desc = dma_desc;

	list_add_tail(&desc->node, &nandc->desc_list);

	return 0;
}

/*
 * Prepares the data descriptor for BAM DMA which will be used for NAND
 * data reads and writes.
 */
static int prep_bam_dma_desc_data(struct qcom_nand_controller *nandc, bool read,
				  const void *vaddr,
				  int size, unsigned int flags)
{
	int ret;
	struct bam_transaction *bam_txn = nandc->bam_txn;

	if (read) {
		sg_set_buf(&bam_txn->data_sgl[bam_txn->rx_sgl_pos],
			   vaddr, size);
		bam_txn->rx_sgl_pos++;
	} else {
		sg_set_buf(&bam_txn->data_sgl[bam_txn->tx_sgl_pos],
			   vaddr, size);
		bam_txn->tx_sgl_pos++;

		/*
		 * BAM will only set EOT for DMA_PREP_INTERRUPT so if this flag
		 * is not set, form the DMA descriptor
		 */
		if (!(flags & NAND_BAM_NO_EOT)) {
			ret = prepare_bam_async_desc(nandc, nandc->tx_chan,
						     DMA_PREP_INTERRUPT);
			if (ret)
				return ret;
		}
	}

	return 0;
}

static int prep_adm_dma_desc(struct qcom_nand_controller *nandc, bool read,
			     int reg_off, const void *vaddr, int size,
			     bool flow_control)
{
	struct desc_info *desc;
	struct dma_async_tx_descriptor *dma_desc;
	struct scatterlist *sgl;
	struct dma_slave_config slave_conf;
	enum dma_transfer_direction dir_eng;
	int ret;

	desc = kzalloc(sizeof(*desc), GFP_KERNEL);
	if (!desc)
		return -ENOMEM;

	sgl = &desc->adm_sgl;

	sg_init_one(sgl, vaddr, size);

	if (read) {
		dir_eng = DMA_DEV_TO_MEM;
		desc->dir = DMA_FROM_DEVICE;
	} else {
		dir_eng = DMA_MEM_TO_DEV;
		desc->dir = DMA_TO_DEVICE;
	}

	ret = dma_map_sg(nandc->dev, sgl, 1, desc->dir);
	if (ret == 0) {
		ret = -ENOMEM;
		goto err;
	}

	memset(&slave_conf, 0x00, sizeof(slave_conf));

	slave_conf.device_fc = flow_control;
	if (read) {
		slave_conf.src_maxburst = 16;
		slave_conf.src_addr = nandc->base_dma + reg_off;
		slave_conf.slave_id = nandc->data_crci;
	} else {
		slave_conf.dst_maxburst = 16;
		slave_conf.dst_addr = nandc->base_dma + reg_off;
		slave_conf.slave_id = nandc->cmd_crci;
	}

	ret = dmaengine_slave_config(nandc->chan, &slave_conf);
	if (ret) {
		dev_err(nandc->dev, "failed to configure dma channel\n");
		goto err;
	}

	dma_desc = dmaengine_prep_slave_sg(nandc->chan, sgl, 1, dir_eng, 0);
	if (!dma_desc) {
		dev_err(nandc->dev, "failed to prepare desc\n");
		ret = -EINVAL;
		goto err;
	}

	desc->dma_desc = dma_desc;

	list_add_tail(&desc->node, &nandc->desc_list);

	return 0;
err:
	kfree(desc);

	return ret;
}

/*
 * read_reg_dma:	prepares a descriptor to read a given number of
 *			contiguous registers to the reg_read_buf pointer
 *
 * @first:		offset of the first register in the contiguous block
 * @num_regs:		number of registers to read
 * @flags:		flags to control DMA descriptor preparation
 */
static int read_reg_dma(struct qcom_nand_controller *nandc, int first,
			int num_regs, unsigned int flags)
{
	bool flow_control = false;
	void *vaddr;
	int size;

	if (first == NAND_READ_ID || first == NAND_FLASH_STATUS)
		flow_control = true;

	size = num_regs * sizeof(u32);
	vaddr = nandc->reg_read_buf + nandc->reg_read_pos;
	nandc->reg_read_pos += num_regs;

	return prep_adm_dma_desc(nandc, true, first, vaddr, size, flow_control);
}

/*
 * write_reg_dma:	prepares a descriptor to write a given number of
 *			contiguous registers
 *
 * @first:		offset of the first register in the contiguous block
 * @num_regs:		number of registers to write
 * @flags:		flags to control DMA descriptor preparation
 */
static int write_reg_dma(struct qcom_nand_controller *nandc, int first,
			 int num_regs, unsigned int flags)
{
	bool flow_control = false;
	struct nandc_regs *regs = nandc->regs;
	void *vaddr;
	int size;

	vaddr = offset_to_nandc_reg(regs, first);

	if (first == NAND_FLASH_CMD)
		flow_control = true;

	if (first == NAND_ERASED_CW_DETECT_CFG) {
		if (flags & NAND_ERASED_CW_SET)
			vaddr = &regs->erased_cw_detect_cfg_set;
		else
			vaddr = &regs->erased_cw_detect_cfg_clr;
	}

	if (first == NAND_EXEC_CMD)
		flags |= NAND_BAM_NWD;

	if (first == NAND_DEV_CMD1_RESTORE)
		first = NAND_DEV_CMD1;

	if (first == NAND_DEV_CMD_VLD_RESTORE)
		first = NAND_DEV_CMD_VLD;

	size = num_regs * sizeof(u32);

	return prep_adm_dma_desc(nandc, false, first, vaddr, size,
				 flow_control);
}

/*
 * read_data_dma:	prepares a DMA descriptor to transfer data from the
 *			controller's internal buffer to the buffer 'vaddr'
 *
 * @reg_off:		offset within the controller's data buffer
 * @vaddr:		virtual address of the buffer we want to write to
 * @size:		DMA transaction size in bytes
 * @flags:		flags to control DMA descriptor preparation
 */
static int read_data_dma(struct qcom_nand_controller *nandc, int reg_off,
			 const u8 *vaddr, int size, unsigned int flags)
{
	if (nandc->props->is_bam)
		return prep_bam_dma_desc_data(nandc, true, vaddr, size, flags);

	return prep_adm_dma_desc(nandc, true, reg_off, vaddr, size, false);
}

/*
 * write_data_dma:	prepares a DMA descriptor to transfer data from
 *			'vaddr' to the controller's internal buffer
 *
 * @reg_off:		offset within the controller's data buffer
 * @vaddr:		virtual address of the buffer we want to read from
 * @size:		DMA transaction size in bytes
 * @flags:		flags to control DMA descriptor preparation
 */
static int write_data_dma(struct qcom_nand_controller *nandc, int reg_off,
			  const u8 *vaddr, int size, unsigned int flags)
{
	if (nandc->props->is_bam)
		return prep_bam_dma_desc_data(nandc, false, vaddr, size, flags);

	return prep_adm_dma_desc(nandc, false, reg_off, vaddr, size, false);
}

/*
 * Helper to prepare DMA descriptors for configuring registers
 * before reading a NAND page.
 */
static void config_nand_page_read(struct qcom_nand_controller *nandc)
{
	write_reg_dma(nandc, NAND_ADDR0, 2, 0);
	write_reg_dma(nandc, NAND_DEV0_CFG0, 3, 0);
	write_reg_dma(nandc, NAND_EBI2_ECC_BUF_CFG, 1, 0);
	write_reg_dma(nandc, NAND_ERASED_CW_DETECT_CFG, 1, 0);
	write_reg_dma(nandc, NAND_ERASED_CW_DETECT_CFG, 1,
		      NAND_ERASED_CW_SET | NAND_BAM_NEXT_SGL);
}

/*
 * Helper to prepare DMA descriptors for configuring registers
 * before reading each codeword in NAND page.
 */
static void config_nand_cw_read(struct qcom_nand_controller *nandc)
{
	if (nandc->props->is_bam)
		write_reg_dma(nandc, NAND_READ_LOCATION_0, 4,
			      NAND_BAM_NEXT_SGL);

	write_reg_dma(nandc, NAND_FLASH_CMD, 1, NAND_BAM_NEXT_SGL);
	write_reg_dma(nandc, NAND_EXEC_CMD, 1, NAND_BAM_NEXT_SGL);

	read_reg_dma(nandc, NAND_FLASH_STATUS, 2, 0);
	read_reg_dma(nandc, NAND_ERASED_CW_DETECT_STATUS, 1,
		     NAND_BAM_NEXT_SGL);
}

/*
 * Helper to prepare dma descriptors to configure registers needed for reading a
 * single codeword in page
 */
static void config_nand_single_cw_page_read(struct qcom_nand_controller *nandc)
{
	config_nand_page_read(nandc);
	config_nand_cw_read(nandc);
}

/*
 * Helper to prepare DMA descriptors used to configure registers needed for
 * before writing a NAND page.
 */
static void config_nand_page_write(struct qcom_nand_controller *nandc)
{
	write_reg_dma(nandc, NAND_ADDR0, 2, 0);
	write_reg_dma(nandc, NAND_DEV0_CFG0, 3, 0);
	write_reg_dma(nandc, NAND_EBI2_ECC_BUF_CFG, 1,
		      NAND_BAM_NEXT_SGL);
}

/*
 * Helper to prepare DMA descriptors for configuring registers
 * before writing each codeword in NAND page.
 */
static void config_nand_cw_write(struct qcom_nand_controller *nandc)
{
	write_reg_dma(nandc, NAND_FLASH_CMD, 1, NAND_BAM_NEXT_SGL);
	write_reg_dma(nandc, NAND_EXEC_CMD, 1, NAND_BAM_NEXT_SGL);

	read_reg_dma(nandc, NAND_FLASH_STATUS, 1, NAND_BAM_NEXT_SGL);

	write_reg_dma(nandc, NAND_FLASH_STATUS, 1, 0);
	write_reg_dma(nandc, NAND_READ_STATUS, 1, NAND_BAM_NEXT_SGL);
}

/*
 * the following functions are used within chip->cmdfunc() to perform different
 * NAND_CMD_* commands
 */

/* sets up descriptors for NAND_CMD_PARAM */
static int nandc_param(struct qcom_nand_host *host)
{
	struct nand_chip *chip = &host->chip;
	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);

	/*
	 * NAND_CMD_PARAM is called before we know much about the FLASH chip
	 * in use. we configure the controller to perform a raw read of 512
	 * bytes to read onfi params
	 */
	nandc_set_reg(nandc, NAND_FLASH_CMD, PAGE_READ | PAGE_ACC | LAST_PAGE);
	nandc_set_reg(nandc, NAND_ADDR0, 0);
	nandc_set_reg(nandc, NAND_ADDR1, 0);
	nandc_set_reg(nandc, NAND_DEV0_CFG0, 0 << CW_PER_PAGE
					| 512 << UD_SIZE_BYTES
					| 5 << NUM_ADDR_CYCLES
					| 0 << SPARE_SIZE_BYTES);
	nandc_set_reg(nandc, NAND_DEV0_CFG1, 7 << NAND_RECOVERY_CYCLES
					| 0 << CS_ACTIVE_BSY
					| 17 << BAD_BLOCK_BYTE_NUM
					| 1 << BAD_BLOCK_IN_SPARE_AREA
					| 2 << WR_RD_BSY_GAP
					| 0 << WIDE_FLASH
					| 1 << DEV0_CFG1_ECC_DISABLE);
	nandc_set_reg(nandc, NAND_EBI2_ECC_BUF_CFG, 1 << ECC_CFG_ECC_DISABLE);

	/* configure CMD1 and VLD for ONFI param probing */
	nandc_set_reg(nandc, NAND_DEV_CMD_VLD,
		      (nandc->vld & ~READ_START_VLD));
	nandc_set_reg(nandc, NAND_DEV_CMD1,
		      (nandc->cmd1 & ~(0xFF << READ_ADDR))
		      | NAND_CMD_PARAM << READ_ADDR);

	nandc_set_reg(nandc, NAND_EXEC_CMD, 1);

	nandc_set_reg(nandc, NAND_DEV_CMD1_RESTORE, nandc->cmd1);
	nandc_set_reg(nandc, NAND_DEV_CMD_VLD_RESTORE, nandc->vld);
	nandc_set_read_loc(nandc, 0, 0, 512, 1);

	write_reg_dma(nandc, NAND_DEV_CMD_VLD, 1, 0);
	write_reg_dma(nandc, NAND_DEV_CMD1, 1, NAND_BAM_NEXT_SGL);

	nandc->buf_count = 512;
	memset(nandc->data_buffer, 0xff, nandc->buf_count);

	config_nand_single_cw_page_read(nandc);

	read_data_dma(nandc, FLASH_BUF_ACC, nandc->data_buffer,
		      nandc->buf_count, 0);

	/* restore CMD1 and VLD regs */
	write_reg_dma(nandc, NAND_DEV_CMD1_RESTORE, 1, 0);
	write_reg_dma(nandc, NAND_DEV_CMD_VLD_RESTORE, 1, NAND_BAM_NEXT_SGL);

	return 0;
}

/* sets up descriptors for NAND_CMD_ERASE1 */
static int erase_block(struct qcom_nand_host *host, int page_addr)
{
	struct nand_chip *chip = &host->chip;
	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);

	nandc_set_reg(nandc, NAND_FLASH_CMD,
		      BLOCK_ERASE | PAGE_ACC | LAST_PAGE);
	nandc_set_reg(nandc, NAND_ADDR0, page_addr);
	nandc_set_reg(nandc, NAND_ADDR1, 0);
	nandc_set_reg(nandc, NAND_DEV0_CFG0,
		      host->cfg0_raw & ~(7 << CW_PER_PAGE));
	nandc_set_reg(nandc, NAND_DEV0_CFG1, host->cfg1_raw);
	nandc_set_reg(nandc, NAND_EXEC_CMD, 1);
	nandc_set_reg(nandc, NAND_FLASH_STATUS, host->clrflashstatus);
	nandc_set_reg(nandc, NAND_READ_STATUS, host->clrreadstatus);

	write_reg_dma(nandc, NAND_FLASH_CMD, 3, NAND_BAM_NEXT_SGL);
	write_reg_dma(nandc, NAND_DEV0_CFG0, 2, NAND_BAM_NEXT_SGL);
	write_reg_dma(nandc, NAND_EXEC_CMD, 1, NAND_BAM_NEXT_SGL);

	read_reg_dma(nandc, NAND_FLASH_STATUS, 1, NAND_BAM_NEXT_SGL);

	write_reg_dma(nandc, NAND_FLASH_STATUS, 1, 0);
	write_reg_dma(nandc, NAND_READ_STATUS, 1, NAND_BAM_NEXT_SGL);

	return 0;
}

/* sets up descriptors for NAND_CMD_READID */
static int read_id(struct qcom_nand_host *host, int column)
{
	struct nand_chip *chip = &host->chip;
	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);

	if (column == -1)
		return 0;

	nandc_set_reg(nandc, NAND_FLASH_CMD, FETCH_ID);
	nandc_set_reg(nandc, NAND_ADDR0, column);
	nandc_set_reg(nandc, NAND_ADDR1, 0);
	nandc_set_reg(nandc, NAND_FLASH_CHIP_SELECT,
		      nandc->props->is_bam ? 0 : DM_EN);
	nandc_set_reg(nandc, NAND_EXEC_CMD, 1);

	write_reg_dma(nandc, NAND_FLASH_CMD, 4, NAND_BAM_NEXT_SGL);
	write_reg_dma(nandc, NAND_EXEC_CMD, 1, NAND_BAM_NEXT_SGL);

	read_reg_dma(nandc, NAND_READ_ID, 1, NAND_BAM_NEXT_SGL);

	return 0;
}

/* sets up descriptors for NAND_CMD_RESET */
static int reset(struct qcom_nand_host *host)
{
	struct nand_chip *chip = &host->chip;
	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);

	nandc_set_reg(nandc, NAND_FLASH_CMD, RESET_DEVICE);
	nandc_set_reg(nandc, NAND_EXEC_CMD, 1);

	write_reg_dma(nandc, NAND_FLASH_CMD, 1, NAND_BAM_NEXT_SGL);
	write_reg_dma(nandc, NAND_EXEC_CMD, 1, NAND_BAM_NEXT_SGL);

	read_reg_dma(nandc, NAND_FLASH_STATUS, 1, NAND_BAM_NEXT_SGL);

	return 0;
}

/* helpers to submit/free our list of dma descriptors */
static int submit_descs(struct qcom_nand_controller *nandc)
{
	struct desc_info *desc;
	dma_cookie_t cookie = 0;
	struct bam_transaction *bam_txn = nandc->bam_txn;
	int r;

	if (nandc->props->is_bam) {
		if (bam_txn->rx_sgl_pos > bam_txn->rx_sgl_start) {
			r = prepare_bam_async_desc(nandc, nandc->rx_chan, 0);
			if (r)
				return r;
		}

		if (bam_txn->tx_sgl_pos > bam_txn->tx_sgl_start) {
			r = prepare_bam_async_desc(nandc, nandc->tx_chan,
						   DMA_PREP_INTERRUPT);
			if (r)
				return r;
		}

		if (bam_txn->cmd_sgl_pos > bam_txn->cmd_sgl_start) {
			r = prepare_bam_async_desc(nandc, nandc->cmd_chan, 0);
			if (r)
				return r;
		}
	}

	list_for_each_entry(desc, &nandc->desc_list, node)
		cookie = dmaengine_submit(desc->dma_desc);

	if (nandc->props->is_bam) {
		dma_async_issue_pending(nandc->tx_chan);
		dma_async_issue_pending(nandc->rx_chan);

		if (dma_sync_wait(nandc->cmd_chan, cookie) != DMA_COMPLETE)
			return -ETIMEDOUT;
	} else {
		if (dma_sync_wait(nandc->chan, cookie) != DMA_COMPLETE)
			return -ETIMEDOUT;
	}

	return 0;
}

static void free_descs(struct qcom_nand_controller *nandc)
{
	struct desc_info *desc, *n;

	list_for_each_entry_safe(desc, n, &nandc->desc_list, node) {
		list_del(&desc->node);

		if (nandc->props->is_bam)
			dma_unmap_sg(nandc->dev, desc->bam_sgl,
				     desc->sgl_cnt, desc->dir);
		else
			dma_unmap_sg(nandc->dev, &desc->adm_sgl, 1,
				     desc->dir);

		kfree(desc);
	}
}

/* reset the register read buffer for next NAND operation */
static void clear_read_regs(struct qcom_nand_controller *nandc)
{
	nandc->reg_read_pos = 0;
	nandc_read_buffer_sync(nandc, false);
}

static void pre_command(struct qcom_nand_host *host, int command)
{
	struct nand_chip *chip = &host->chip;
	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);

	nandc->buf_count = 0;
	nandc->buf_start = 0;
	host->use_ecc = false;
	host->last_command = command;

	clear_read_regs(nandc);

	if (command == NAND_CMD_RESET || command == NAND_CMD_READID ||
	    command == NAND_CMD_PARAM || command == NAND_CMD_ERASE1)
		clear_bam_transaction(nandc);
}

/*
 * this is called after NAND_CMD_PAGEPROG and NAND_CMD_ERASE1 to set our
 * privately maintained status byte, this status byte can be read after
 * NAND_CMD_STATUS is called
 */
static void parse_erase_write_errors(struct qcom_nand_host *host, int command)
{
	struct nand_chip *chip = &host->chip;
	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);
	struct nand_ecc_ctrl *ecc = &chip->ecc;
	int num_cw;
	int i;

	num_cw = command == NAND_CMD_PAGEPROG ? ecc->steps : 1;
	nandc_read_buffer_sync(nandc, true);

	for (i = 0; i < num_cw; i++) {
		u32 flash_status = le32_to_cpu(nandc->reg_read_buf[i]);

		if (flash_status & FS_MPU_ERR)
			host->status &= ~NAND_STATUS_WP;

		if (flash_status & FS_OP_ERR || (i == (num_cw - 1) &&
						 (flash_status &
						  FS_DEVICE_STS_ERR)))
			host->status |= NAND_STATUS_FAIL;
	}
}

static void post_command(struct qcom_nand_host *host, int command)
{
	struct nand_chip *chip = &host->chip;
	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);

	switch (command) {
	case NAND_CMD_READID:
		nandc_read_buffer_sync(nandc, true);
		memcpy(nandc->data_buffer, nandc->reg_read_buf,
		       nandc->buf_count);
		break;
	case NAND_CMD_PAGEPROG:
	case NAND_CMD_ERASE1:
		parse_erase_write_errors(host, command);
		break;
	default:
		break;
	}
}

/*
 * Implements chip->cmdfunc. It's  only used for a limited set of commands.
 * The rest of the commands wouldn't be called by upper layers. For example,
 * NAND_CMD_READOOB would never be called because we have our own versions
 * of read_oob ops for nand_ecc_ctrl.
 */
static void qcom_nandc_command(struct mtd_info *mtd, unsigned int command,
			       int column, int page_addr)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	struct qcom_nand_host *host = to_qcom_nand_host(chip);
	struct nand_ecc_ctrl *ecc = &chip->ecc;
	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);
	bool wait = false;
	int ret = 0;

	pre_command(host, command);

	switch (command) {
	case NAND_CMD_RESET:
		ret = reset(host);
		wait = true;
		break;

	case NAND_CMD_READID:
		nandc->buf_count = 4;
		ret = read_id(host, column);
		wait = true;
		break;

	case NAND_CMD_PARAM:
		ret = nandc_param(host);
		wait = true;
		break;

	case NAND_CMD_ERASE1:
		ret = erase_block(host, page_addr);
		wait = true;
		break;

	case NAND_CMD_READ0:
		/* we read the entire page for now */
		WARN_ON(column != 0);

		host->use_ecc = true;
		set_address(host, 0, page_addr);
		update_rw_regs(host, ecc->steps, true);
		break;

	case NAND_CMD_SEQIN:
		WARN_ON(column != 0);
		set_address(host, 0, page_addr);
		break;

	case NAND_CMD_PAGEPROG:
	case NAND_CMD_STATUS:
	case NAND_CMD_NONE:
	default:
		break;
	}

	if (ret) {
		dev_err(nandc->dev, "failure executing command %d\n",
			command);
		free_descs(nandc);
		return;
	}

	if (wait) {
		ret = submit_descs(nandc);
		if (ret)
			dev_err(nandc->dev,
				"failure submitting descs for command %d\n",
				command);
	}

	free_descs(nandc);

	post_command(host, command);
}

/*
 * when using BCH ECC, the HW flags an error in NAND_FLASH_STATUS if it read
 * an erased CW, and reports an erased CW in NAND_ERASED_CW_DETECT_STATUS.
 *
 * when using RS ECC, the HW reports the same erros when reading an erased CW,
 * but it notifies that it is an erased CW by placing special characters at
 * certain offsets in the buffer.
 *
 * verify if the page is erased or not, and fix up the page for RS ECC by
 * replacing the special characters with 0xff.
 */
static bool erased_chunk_check_and_fixup(u8 *data_buf, int data_len)
{
	u8 empty1, empty2;

	/*
	 * an erased page flags an error in NAND_FLASH_STATUS, check if the page
	 * is erased by looking for 0x54s at offsets 3 and 175 from the
	 * beginning of each codeword
	 */

	empty1 = data_buf[3];
	empty2 = data_buf[175];

	/*
	 * if the erased codework markers, if they exist override them with
	 * 0xffs
	 */
	if ((empty1 == 0x54 && empty2 == 0xff) ||
	    (empty1 == 0xff && empty2 == 0x54)) {
		data_buf[3] = 0xff;
		data_buf[175] = 0xff;
	}

	/*
	 * check if the entire chunk contains 0xffs or not. if it doesn't, then
	 * restore the original values at the special offsets
	 */
	if (memchr_inv(data_buf, 0xff, data_len)) {
		data_buf[3] = empty1;
		data_buf[175] = empty2;

		return false;
	}

	return true;
}

struct read_stats {
	__le32 flash;
	__le32 buffer;
	__le32 erased_cw;
};

/*
 * reads back status registers set by the controller to notify page read
 * errors. this is equivalent to what 'ecc->correct()' would do.
 */
static int parse_read_errors(struct qcom_nand_host *host, u8 *data_buf,
			     u8 *oob_buf)
{
	struct nand_chip *chip = &host->chip;
	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);
	struct mtd_info *mtd = nand_to_mtd(chip);
	struct nand_ecc_ctrl *ecc = &chip->ecc;
	unsigned int max_bitflips = 0;
	struct read_stats *buf;
	int i;

	buf = (struct read_stats *)nandc->reg_read_buf;
	nandc_read_buffer_sync(nandc, true);

	for (i = 0; i < ecc->steps; i++, buf++) {
		u32 flash, buffer, erased_cw;
		int data_len, oob_len;

		if (i == (ecc->steps - 1)) {
			data_len = ecc->size - ((ecc->steps - 1) << 2);
			oob_len = ecc->steps << 2;
		} else {
			data_len = host->cw_data;
			oob_len = 0;
		}

		flash = le32_to_cpu(buf->flash);
		buffer = le32_to_cpu(buf->buffer);
		erased_cw = le32_to_cpu(buf->erased_cw);

		if (flash & (FS_OP_ERR | FS_MPU_ERR)) {
			bool erased;

			/* ignore erased codeword errors */
			if (host->bch_enabled) {
				erased = (erased_cw & ERASED_CW) == ERASED_CW ?
					 true : false;
			} else {
				erased = erased_chunk_check_and_fixup(data_buf,
								      data_len);
			}

			if (erased) {
				data_buf += data_len;
				if (oob_buf)
					oob_buf += oob_len + ecc->bytes;
				continue;
			}

			if (buffer & BS_UNCORRECTABLE_BIT) {
				int ret, ecclen, extraooblen;
				void *eccbuf;

				eccbuf = oob_buf ? oob_buf + oob_len : NULL;
				ecclen = oob_buf ? host->ecc_bytes_hw : 0;
				extraooblen = oob_buf ? oob_len : 0;

				/*
				 * make sure it isn't an erased page reported
				 * as not-erased by HW because of a few bitflips
				 */
				ret = nand_check_erased_ecc_chunk(data_buf,
					data_len, eccbuf, ecclen, oob_buf,
					extraooblen, ecc->strength);
				if (ret < 0) {
					mtd->ecc_stats.failed++;
				} else {
					mtd->ecc_stats.corrected += ret;
					max_bitflips =
						max_t(unsigned int, max_bitflips, ret);
				}
			}
		} else {
			unsigned int stat;

			stat = buffer & BS_CORRECTABLE_ERR_MSK;
			mtd->ecc_stats.corrected += stat;
			max_bitflips = max(max_bitflips, stat);
		}

		data_buf += data_len;
		if (oob_buf)
			oob_buf += oob_len + ecc->bytes;
	}

	return max_bitflips;
}

/*
 * helper to perform the actual page read operation, used by ecc->read_page(),
 * ecc->read_oob()
 */
static int read_page_ecc(struct qcom_nand_host *host, u8 *data_buf,
			 u8 *oob_buf)
{
	struct nand_chip *chip = &host->chip;
	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);
	struct nand_ecc_ctrl *ecc = &chip->ecc;
	int i, ret;

	config_nand_page_read(nandc);

	/* queue cmd descs for each codeword */
	for (i = 0; i < ecc->steps; i++) {
		int data_size, oob_size;

		if (i == (ecc->steps - 1)) {
			data_size = ecc->size - ((ecc->steps - 1) << 2);
			oob_size = (ecc->steps << 2) + host->ecc_bytes_hw +
				   host->spare_bytes;
		} else {
			data_size = host->cw_data;
			oob_size = host->ecc_bytes_hw + host->spare_bytes;
		}

		if (nandc->props->is_bam) {
			if (data_buf && oob_buf) {
				nandc_set_read_loc(nandc, 0, 0, data_size, 0);
				nandc_set_read_loc(nandc, 1, data_size,
						   oob_size, 1);
			} else if (data_buf) {
				nandc_set_read_loc(nandc, 0, 0, data_size, 1);
			} else {
				nandc_set_read_loc(nandc, 0, data_size,
						   oob_size, 1);
			}
		}

		config_nand_cw_read(nandc);

		if (data_buf)
			read_data_dma(nandc, FLASH_BUF_ACC, data_buf,
				      data_size, 0);

		/*
		 * when ecc is enabled, the controller doesn't read the real
		 * or dummy bad block markers in each chunk. To maintain a
		 * consistent layout across RAW and ECC reads, we just
		 * leave the real/dummy BBM offsets empty (i.e, filled with
		 * 0xffs)
		 */
		if (oob_buf) {
			int j;

			for (j = 0; j < host->bbm_size; j++)
				*oob_buf++ = 0xff;

			read_data_dma(nandc, FLASH_BUF_ACC + data_size,
				      oob_buf, oob_size, 0);
		}

		if (data_buf)
			data_buf += data_size;
		if (oob_buf)
			oob_buf += oob_size;
	}

	ret = submit_descs(nandc);
	if (ret)
		dev_err(nandc->dev, "failure to read page/oob\n");

	free_descs(nandc);

	return ret;
}

/*
 * a helper that copies the last step/codeword of a page (containing free oob)
 * into our local buffer
 */
static int copy_last_cw(struct qcom_nand_host *host, int page)
{
	struct nand_chip *chip = &host->chip;
	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);
	struct nand_ecc_ctrl *ecc = &chip->ecc;
	int size;
	int ret;

	clear_read_regs(nandc);

	size = host->use_ecc ? host->cw_data : host->cw_size;

	/* prepare a clean read buffer */
	memset(nandc->data_buffer, 0xff, size);

	set_address(host, host->cw_size * (ecc->steps - 1), page);
	update_rw_regs(host, 1, true);

	config_nand_single_cw_page_read(nandc);

	read_data_dma(nandc, FLASH_BUF_ACC, nandc->data_buffer, size, 0);

	ret = submit_descs(nandc);
	if (ret)
		dev_err(nandc->dev, "failed to copy last codeword\n");

	free_descs(nandc);

	return ret;
}

/* implements ecc->read_page() */
static int qcom_nandc_read_page(struct mtd_info *mtd, struct nand_chip *chip,
				uint8_t *buf, int oob_required, int page)
{
	struct qcom_nand_host *host = to_qcom_nand_host(chip);
	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);
	u8 *data_buf, *oob_buf = NULL;
	int ret;

	data_buf = buf;
	oob_buf = oob_required ? chip->oob_poi : NULL;

	clear_bam_transaction(nandc);
	ret = read_page_ecc(host, data_buf, oob_buf);
	if (ret) {
		dev_err(nandc->dev, "failure to read page\n");
		return ret;
	}

	return parse_read_errors(host, data_buf, oob_buf);
}

/* implements ecc->read_page_raw() */
static int qcom_nandc_read_page_raw(struct mtd_info *mtd,
				    struct nand_chip *chip, uint8_t *buf,
				    int oob_required, int page)
{
	struct qcom_nand_host *host = to_qcom_nand_host(chip);
	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);
	u8 *data_buf, *oob_buf;
	struct nand_ecc_ctrl *ecc = &chip->ecc;
	int i, ret;
	int read_loc;

	data_buf = buf;
	oob_buf = chip->oob_poi;

	host->use_ecc = false;

	clear_bam_transaction(nandc);
	update_rw_regs(host, ecc->steps, true);
	config_nand_page_read(nandc);

	for (i = 0; i < ecc->steps; i++) {
		int data_size1, data_size2, oob_size1, oob_size2;
		int reg_off = FLASH_BUF_ACC;

		data_size1 = mtd->writesize - host->cw_size * (ecc->steps - 1);
		oob_size1 = host->bbm_size;

		if (i == (ecc->steps - 1)) {
			data_size2 = ecc->size - data_size1 -
				     ((ecc->steps - 1) << 2);
			oob_size2 = (ecc->steps << 2) + host->ecc_bytes_hw +
				    host->spare_bytes;
		} else {
			data_size2 = host->cw_data - data_size1;
			oob_size2 = host->ecc_bytes_hw + host->spare_bytes;
		}

		if (nandc->props->is_bam) {
			read_loc = 0;
			nandc_set_read_loc(nandc, 0, read_loc, data_size1, 0);
			read_loc += data_size1;

			nandc_set_read_loc(nandc, 1, read_loc, oob_size1, 0);
			read_loc += oob_size1;

			nandc_set_read_loc(nandc, 2, read_loc, data_size2, 0);
			read_loc += data_size2;

			nandc_set_read_loc(nandc, 3, read_loc, oob_size2, 1);
		}

		config_nand_cw_read(nandc);

		read_data_dma(nandc, reg_off, data_buf, data_size1, 0);
		reg_off += data_size1;
		data_buf += data_size1;

		read_data_dma(nandc, reg_off, oob_buf, oob_size1, 0);
		reg_off += oob_size1;
		oob_buf += oob_size1;

		read_data_dma(nandc, reg_off, data_buf, data_size2, 0);
		reg_off += data_size2;
		data_buf += data_size2;

		read_data_dma(nandc, reg_off, oob_buf, oob_size2, 0);
		oob_buf += oob_size2;
	}

	ret = submit_descs(nandc);
	if (ret)
		dev_err(nandc->dev, "failure to read raw page\n");

	free_descs(nandc);

	return 0;
}

/* implements ecc->read_oob() */
static int qcom_nandc_read_oob(struct mtd_info *mtd, struct nand_chip *chip,
			       int page)
{
	struct qcom_nand_host *host = to_qcom_nand_host(chip);
	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);
	struct nand_ecc_ctrl *ecc = &chip->ecc;
	int ret;

	clear_read_regs(nandc);
	clear_bam_transaction(nandc);

	host->use_ecc = true;
	set_address(host, 0, page);
	update_rw_regs(host, ecc->steps, true);

	ret = read_page_ecc(host, NULL, chip->oob_poi);
	if (ret)
		dev_err(nandc->dev, "failure to read oob\n");

	return ret;
}

/* implements ecc->write_page() */
static int qcom_nandc_write_page(struct mtd_info *mtd, struct nand_chip *chip,
				 const uint8_t *buf, int oob_required, int page)
{
	struct qcom_nand_host *host = to_qcom_nand_host(chip);
	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);
	struct nand_ecc_ctrl *ecc = &chip->ecc;
	u8 *data_buf, *oob_buf;
	int i, ret;

	clear_read_regs(nandc);
	clear_bam_transaction(nandc);

	data_buf = (u8 *)buf;
	oob_buf = chip->oob_poi;

	host->use_ecc = true;
	update_rw_regs(host, ecc->steps, false);
	config_nand_page_write(nandc);

	for (i = 0; i < ecc->steps; i++) {
		int data_size, oob_size;

		if (i == (ecc->steps - 1)) {
			data_size = ecc->size - ((ecc->steps - 1) << 2);
			oob_size = (ecc->steps << 2) + host->ecc_bytes_hw +
				   host->spare_bytes;
		} else {
			data_size = host->cw_data;
			oob_size = ecc->bytes;
		}


		write_data_dma(nandc, FLASH_BUF_ACC, data_buf, data_size,
			       i == (ecc->steps - 1) ? NAND_BAM_NO_EOT : 0);

		/*
		 * when ECC is enabled, we don't really need to write anything
		 * to oob for the first n - 1 codewords since these oob regions
		 * just contain ECC bytes that's written by the controller
		 * itself. For the last codeword, we skip the bbm positions and
		 * write to the free oob area.
		 */
		if (i == (ecc->steps - 1)) {
			oob_buf += host->bbm_size;

			write_data_dma(nandc, FLASH_BUF_ACC + data_size,
				       oob_buf, oob_size, 0);
		}

		config_nand_cw_write(nandc);

		data_buf += data_size;
		oob_buf += oob_size;
	}

	ret = submit_descs(nandc);
	if (ret)
		dev_err(nandc->dev, "failure to write page\n");

	free_descs(nandc);

	return ret;
}

/* implements ecc->write_page_raw() */
static int qcom_nandc_write_page_raw(struct mtd_info *mtd,
				     struct nand_chip *chip, const uint8_t *buf,
				     int oob_required, int page)
{
	struct qcom_nand_host *host = to_qcom_nand_host(chip);
	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);
	struct nand_ecc_ctrl *ecc = &chip->ecc;
	u8 *data_buf, *oob_buf;
	int i, ret;

	clear_read_regs(nandc);
	clear_bam_transaction(nandc);

	data_buf = (u8 *)buf;
	oob_buf = chip->oob_poi;

	host->use_ecc = false;
	update_rw_regs(host, ecc->steps, false);
	config_nand_page_write(nandc);

	for (i = 0; i < ecc->steps; i++) {
		int data_size1, data_size2, oob_size1, oob_size2;
		int reg_off = FLASH_BUF_ACC;

		data_size1 = mtd->writesize - host->cw_size * (ecc->steps - 1);
		oob_size1 = host->bbm_size;

		if (i == (ecc->steps - 1)) {
			data_size2 = ecc->size - data_size1 -
				     ((ecc->steps - 1) << 2);
			oob_size2 = (ecc->steps << 2) + host->ecc_bytes_hw +
				    host->spare_bytes;
		} else {
			data_size2 = host->cw_data - data_size1;
			oob_size2 = host->ecc_bytes_hw + host->spare_bytes;
		}

		write_data_dma(nandc, reg_off, data_buf, data_size1,
			       NAND_BAM_NO_EOT);
		reg_off += data_size1;
		data_buf += data_size1;

		write_data_dma(nandc, reg_off, oob_buf, oob_size1,
			       NAND_BAM_NO_EOT);
		reg_off += oob_size1;
		oob_buf += oob_size1;

		write_data_dma(nandc, reg_off, data_buf, data_size2,
			       NAND_BAM_NO_EOT);
		reg_off += data_size2;
		data_buf += data_size2;

		write_data_dma(nandc, reg_off, oob_buf, oob_size2, 0);
		oob_buf += oob_size2;

		config_nand_cw_write(nandc);
	}

	ret = submit_descs(nandc);
	if (ret)
		dev_err(nandc->dev, "failure to write raw page\n");

	free_descs(nandc);

	return ret;
}

/*
 * implements ecc->write_oob()
 *
 * the NAND controller cannot write only data or only oob within a codeword,
 * since ecc is calculated for the combined codeword. we first copy the
 * entire contents for the last codeword(data + oob), replace the old oob
 * with the new one in chip->oob_poi, and then write the entire codeword.
 * this read-copy-write operation results in a slight performance loss.
 */
static int qcom_nandc_write_oob(struct mtd_info *mtd, struct nand_chip *chip,
				int page)
{
	struct qcom_nand_host *host = to_qcom_nand_host(chip);
	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);
	struct nand_ecc_ctrl *ecc = &chip->ecc;
	u8 *oob = chip->oob_poi;
	int data_size, oob_size;
	int ret, status = 0;

	host->use_ecc = true;

	clear_bam_transaction(nandc);
	ret = copy_last_cw(host, page);
	if (ret)
		return ret;

	clear_read_regs(nandc);
	clear_bam_transaction(nandc);

	/* calculate the data and oob size for the last codeword/step */
	data_size = ecc->size - ((ecc->steps - 1) << 2);
	oob_size = mtd->oobavail;

	/* override new oob content to last codeword */
	mtd_ooblayout_get_databytes(mtd, nandc->data_buffer + data_size, oob,
				    0, mtd->oobavail);

	set_address(host, host->cw_size * (ecc->steps - 1), page);
	update_rw_regs(host, 1, false);

	config_nand_page_write(nandc);
	write_data_dma(nandc, FLASH_BUF_ACC,
		       nandc->data_buffer, data_size + oob_size, 0);
	config_nand_cw_write(nandc);

	ret = submit_descs(nandc);

	free_descs(nandc);

	if (ret) {
		dev_err(nandc->dev, "failure to write oob\n");
		return -EIO;
	}

	chip->cmdfunc(mtd, NAND_CMD_PAGEPROG, -1, -1);

	status = chip->waitfunc(mtd, chip);

	return status & NAND_STATUS_FAIL ? -EIO : 0;
}

static int qcom_nandc_block_bad(struct mtd_info *mtd, loff_t ofs)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	struct qcom_nand_host *host = to_qcom_nand_host(chip);
	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);
	struct nand_ecc_ctrl *ecc = &chip->ecc;
	int page, ret, bbpos, bad = 0;
	u32 flash_status;

	page = (int)(ofs >> chip->page_shift) & chip->pagemask;

	/*
	 * configure registers for a raw sub page read, the address is set to
	 * the beginning of the last codeword, we don't care about reading ecc
	 * portion of oob. we just want the first few bytes from this codeword
	 * that contains the BBM
	 */
	host->use_ecc = false;

	clear_bam_transaction(nandc);
	ret = copy_last_cw(host, page);
	if (ret)
		goto err;

	flash_status = le32_to_cpu(nandc->reg_read_buf[0]);

	if (flash_status & (FS_OP_ERR | FS_MPU_ERR)) {
		dev_warn(nandc->dev, "error when trying to read BBM\n");
		goto err;
	}

	bbpos = mtd->writesize - host->cw_size * (ecc->steps - 1);

	bad = nandc->data_buffer[bbpos] != 0xff;

	if (chip->options & NAND_BUSWIDTH_16)
		bad = bad || (nandc->data_buffer[bbpos + 1] != 0xff);
err:
	return bad;
}

static int qcom_nandc_block_markbad(struct mtd_info *mtd, loff_t ofs)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	struct qcom_nand_host *host = to_qcom_nand_host(chip);
	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);
	struct nand_ecc_ctrl *ecc = &chip->ecc;
	int page, ret, status = 0;

	clear_read_regs(nandc);
	clear_bam_transaction(nandc);

	/*
	 * to mark the BBM as bad, we flash the entire last codeword with 0s.
	 * we don't care about the rest of the content in the codeword since
	 * we aren't going to use this block again
	 */
	memset(nandc->data_buffer, 0x00, host->cw_size);

	page = (int)(ofs >> chip->page_shift) & chip->pagemask;

	/* prepare write */
	host->use_ecc = false;
	set_address(host, host->cw_size * (ecc->steps - 1), page);
	update_rw_regs(host, 1, false);

	config_nand_page_write(nandc);
	write_data_dma(nandc, FLASH_BUF_ACC,
		       nandc->data_buffer, host->cw_size, 0);
	config_nand_cw_write(nandc);

	ret = submit_descs(nandc);

	free_descs(nandc);

	if (ret) {
		dev_err(nandc->dev, "failure to update BBM\n");
		return -EIO;
	}

	chip->cmdfunc(mtd, NAND_CMD_PAGEPROG, -1, -1);

	status = chip->waitfunc(mtd, chip);

	return status & NAND_STATUS_FAIL ? -EIO : 0;
}

/*
 * the three functions below implement chip->read_byte(), chip->read_buf()
 * and chip->write_buf() respectively. these aren't used for
 * reading/writing page data, they are used for smaller data like reading
 * id, status etc
 */
static uint8_t qcom_nandc_read_byte(struct mtd_info *mtd)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	struct qcom_nand_host *host = to_qcom_nand_host(chip);
	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);
	u8 *buf = nandc->data_buffer;
	u8 ret = 0x0;

	if (host->last_command == NAND_CMD_STATUS) {
		ret = host->status;

		host->status = NAND_STATUS_READY | NAND_STATUS_WP;

		return ret;
	}

	if (nandc->buf_start < nandc->buf_count)
		ret = buf[nandc->buf_start++];

	return ret;
}

static void qcom_nandc_read_buf(struct mtd_info *mtd, uint8_t *buf, int len)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);
	int real_len = min_t(size_t, len, nandc->buf_count - nandc->buf_start);

	memcpy(buf, nandc->data_buffer + nandc->buf_start, real_len);
	nandc->buf_start += real_len;
}

static void qcom_nandc_write_buf(struct mtd_info *mtd, const uint8_t *buf,
				 int len)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);
	int real_len = min_t(size_t, len, nandc->buf_count - nandc->buf_start);

	memcpy(nandc->data_buffer + nandc->buf_start, buf, real_len);

	nandc->buf_start += real_len;
}

/* we support only one external chip for now */
static void qcom_nandc_select_chip(struct mtd_info *mtd, int chipnr)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);

	if (chipnr <= 0)
		return;

	dev_warn(nandc->dev, "invalid chip select\n");
}

/*
 * NAND controller page layout info
 *
 * Layout with ECC enabled:
 *
 * |----------------------|  |---------------------------------|
 * |           xx.......yy|  |             *********xx.......yy|
 * |    DATA   xx..ECC..yy|  |    DATA     **SPARE**xx..ECC..yy|
 * |   (516)   xx.......yy|  |  (516-n*4)  **(n*4)**xx.......yy|
 * |           xx.......yy|  |             *********xx.......yy|
 * |----------------------|  |---------------------------------|
 *     codeword 1,2..n-1                  codeword n
 *  <---(528/532 Bytes)-->    <-------(528/532 Bytes)--------->
 *
 * n = Number of codewords in the page
 * . = ECC bytes
 * * = Spare/free bytes
 * x = Unused byte(s)
 * y = Reserved byte(s)
 *
 * 2K page: n = 4, spare = 16 bytes
 * 4K page: n = 8, spare = 32 bytes
 * 8K page: n = 16, spare = 64 bytes
 *
 * the qcom nand controller operates at a sub page/codeword level. each
 * codeword is 528 and 532 bytes for 4 bit and 8 bit ECC modes respectively.
 * the number of ECC bytes vary based on the ECC strength and the bus width.
 *
 * the first n - 1 codewords contains 516 bytes of user data, the remaining
 * 12/16 bytes consist of ECC and reserved data. The nth codeword contains
 * both user data and spare(oobavail) bytes that sum up to 516 bytes.
 *
 * When we access a page with ECC enabled, the reserved bytes(s) are not
 * accessible at all. When reading, we fill up these unreadable positions
 * with 0xffs. When writing, the controller skips writing the inaccessible
 * bytes.
 *
 * Layout with ECC disabled:
 *
 * |------------------------------|  |---------------------------------------|
 * |         yy          xx.......|  |         bb          *********xx.......|
 * |  DATA1  yy  DATA2   xx..ECC..|  |  DATA1  bb  DATA2   **SPARE**xx..ECC..|
 * | (size1) yy (size2)  xx.......|  | (size1) bb (size2)  **(n*4)**xx.......|
 * |         yy          xx.......|  |         bb          *********xx.......|
 * |------------------------------|  |---------------------------------------|
 *         codeword 1,2..n-1                        codeword n
 *  <-------(528/532 Bytes)------>    <-----------(528/532 Bytes)----------->
 *
 * n = Number of codewords in the page
 * . = ECC bytes
 * * = Spare/free bytes
 * x = Unused byte(s)
 * y = Dummy Bad Bock byte(s)
 * b = Real Bad Block byte(s)
 * size1/size2 = function of codeword size and 'n'
 *
 * when the ECC block is disabled, one reserved byte (or two for 16 bit bus
 * width) is now accessible. For the first n - 1 codewords, these are dummy Bad
 * Block Markers. In the last codeword, this position contains the real BBM
 *
 * In order to have a consistent layout between RAW and ECC modes, we assume
 * the following OOB layout arrangement:
 *
 * |-----------|  |--------------------|
 * |yyxx.......|  |bb*********xx.......|
 * |yyxx..ECC..|  |bb*FREEOOB*xx..ECC..|
 * |yyxx.......|  |bb*********xx.......|
 * |yyxx.......|  |bb*********xx.......|
 * |-----------|  |--------------------|
 *  first n - 1       nth OOB region
 *  OOB regions
 *
 * n = Number of codewords in the page
 * . = ECC bytes
 * * = FREE OOB bytes
 * y = Dummy bad block byte(s) (inaccessible when ECC enabled)
 * x = Unused byte(s)
 * b = Real bad block byte(s) (inaccessible when ECC enabled)
 *
 * This layout is read as is when ECC is disabled. When ECC is enabled, the
 * inaccessible Bad Block byte(s) are ignored when we write to a page/oob,
 * and assumed as 0xffs when we read a page/oob. The ECC, unused and
 * dummy/real bad block bytes are grouped as ecc bytes (i.e, ecc->bytes is
 * the sum of the three).
 */
static int qcom_nand_ooblayout_ecc(struct mtd_info *mtd, int section,
				   struct mtd_oob_region *oobregion)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	struct qcom_nand_host *host = to_qcom_nand_host(chip);
	struct nand_ecc_ctrl *ecc = &chip->ecc;

	if (section > 1)
		return -ERANGE;

	if (!section) {
		oobregion->length = (ecc->bytes * (ecc->steps - 1)) +
				    host->bbm_size;
		oobregion->offset = 0;
	} else {
		oobregion->length = host->ecc_bytes_hw + host->spare_bytes;
		oobregion->offset = mtd->oobsize - oobregion->length;
	}

	return 0;
}

static int qcom_nand_ooblayout_free(struct mtd_info *mtd, int section,
				     struct mtd_oob_region *oobregion)
{
	struct nand_chip *chip = mtd_to_nand(mtd);
	struct qcom_nand_host *host = to_qcom_nand_host(chip);
	struct nand_ecc_ctrl *ecc = &chip->ecc;

	if (section)
		return -ERANGE;

	oobregion->length = ecc->steps * 4;
	oobregion->offset = ((ecc->steps - 1) * ecc->bytes) + host->bbm_size;

	return 0;
}

static const struct mtd_ooblayout_ops qcom_nand_ooblayout_ops = {
	.ecc = qcom_nand_ooblayout_ecc,
	.free = qcom_nand_ooblayout_free,
};

static int qcom_nand_host_setup(struct qcom_nand_host *host)
{
	struct nand_chip *chip = &host->chip;
	struct mtd_info *mtd = nand_to_mtd(chip);
	struct nand_ecc_ctrl *ecc = &chip->ecc;
	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);
	int cwperpage, bad_block_byte;
	bool wide_bus;
	int ecc_mode = 1;

	/*
	 * the controller requires each step consists of 512 bytes of data.
	 * bail out if DT has populated a wrong step size.
	 */
	if (ecc->size != NANDC_STEP_SIZE) {
		dev_err(nandc->dev, "invalid ecc size\n");
		return -EINVAL;
	}

	wide_bus = chip->options & NAND_BUSWIDTH_16 ? true : false;

	if (ecc->strength >= 8) {
		/* 8 bit ECC defaults to BCH ECC on all platforms */
		host->bch_enabled = true;
		ecc_mode = 1;

		if (wide_bus) {
			host->ecc_bytes_hw = 14;
			host->spare_bytes = 0;
			host->bbm_size = 2;
		} else {
			host->ecc_bytes_hw = 13;
			host->spare_bytes = 2;
			host->bbm_size = 1;
		}
	} else {
		/*
		 * if the controller supports BCH for 4 bit ECC, the controller
		 * uses lesser bytes for ECC. If RS is used, the ECC bytes is
		 * always 10 bytes
		 */
		if (nandc->props->ecc_modes & ECC_BCH_4BIT) {
			/* BCH */
			host->bch_enabled = true;
			ecc_mode = 0;

			if (wide_bus) {
				host->ecc_bytes_hw = 8;
				host->spare_bytes = 2;
				host->bbm_size = 2;
			} else {
				host->ecc_bytes_hw = 7;
				host->spare_bytes = 4;
				host->bbm_size = 1;
			}
		} else {
			/* RS */
			host->ecc_bytes_hw = 10;

			if (wide_bus) {
				host->spare_bytes = 0;
				host->bbm_size = 2;
			} else {
				host->spare_bytes = 1;
				host->bbm_size = 1;
			}
		}
	}

	/*
	 * we consider ecc->bytes as the sum of all the non-data content in a
	 * step. It gives us a clean representation of the oob area (even if
	 * all the bytes aren't used for ECC).It is always 16 bytes for 8 bit
	 * ECC and 12 bytes for 4 bit ECC
	 */
	ecc->bytes = host->ecc_bytes_hw + host->spare_bytes + host->bbm_size;

	ecc->read_page		= qcom_nandc_read_page;
	ecc->read_page_raw	= qcom_nandc_read_page_raw;
	ecc->read_oob		= qcom_nandc_read_oob;
	ecc->write_page		= qcom_nandc_write_page;
	ecc->write_page_raw	= qcom_nandc_write_page_raw;
	ecc->write_oob		= qcom_nandc_write_oob;

	ecc->mode = NAND_ECC_HW;

	mtd_set_ooblayout(mtd, &qcom_nand_ooblayout_ops);

	cwperpage = mtd->writesize / ecc->size;
	nandc->max_cwperpage = max_t(unsigned int, nandc->max_cwperpage,
				     cwperpage);

	/*
	 * DATA_UD_BYTES varies based on whether the read/write command protects
	 * spare data with ECC too. We protect spare data by default, so we set
	 * it to main + spare data, which are 512 and 4 bytes respectively.
	 */
	host->cw_data = 516;

	/*
	 * total bytes in a step, either 528 bytes for 4 bit ECC, or 532 bytes
	 * for 8 bit ECC
	 */
	host->cw_size = host->cw_data + ecc->bytes;

	if (ecc->bytes * (mtd->writesize / ecc->size) > mtd->oobsize) {
		dev_err(nandc->dev, "ecc data doesn't fit in OOB area\n");
		return -EINVAL;
	}

	bad_block_byte = mtd->writesize - host->cw_size * (cwperpage - 1) + 1;

	host->cfg0 = (cwperpage - 1) << CW_PER_PAGE
				| host->cw_data << UD_SIZE_BYTES
				| 0 << DISABLE_STATUS_AFTER_WRITE
				| 5 << NUM_ADDR_CYCLES
				| host->ecc_bytes_hw << ECC_PARITY_SIZE_BYTES_RS
				| 0 << STATUS_BFR_READ
				| 1 << SET_RD_MODE_AFTER_STATUS
				| host->spare_bytes << SPARE_SIZE_BYTES;

	host->cfg1 = 7 << NAND_RECOVERY_CYCLES
				| 0 <<  CS_ACTIVE_BSY
				| bad_block_byte << BAD_BLOCK_BYTE_NUM
				| 0 << BAD_BLOCK_IN_SPARE_AREA
				| 2 << WR_RD_BSY_GAP
				| wide_bus << WIDE_FLASH
				| host->bch_enabled << ENABLE_BCH_ECC;

	host->cfg0_raw = (cwperpage - 1) << CW_PER_PAGE
				| host->cw_size << UD_SIZE_BYTES
				| 5 << NUM_ADDR_CYCLES
				| 0 << SPARE_SIZE_BYTES;

	host->cfg1_raw = 7 << NAND_RECOVERY_CYCLES
				| 0 << CS_ACTIVE_BSY
				| 17 << BAD_BLOCK_BYTE_NUM
				| 1 << BAD_BLOCK_IN_SPARE_AREA
				| 2 << WR_RD_BSY_GAP
				| wide_bus << WIDE_FLASH
				| 1 << DEV0_CFG1_ECC_DISABLE;

	host->ecc_bch_cfg = !host->bch_enabled << ECC_CFG_ECC_DISABLE
				| 0 << ECC_SW_RESET
				| host->cw_data << ECC_NUM_DATA_BYTES
				| 1 << ECC_FORCE_CLK_OPEN
				| ecc_mode << ECC_MODE
				| host->ecc_bytes_hw << ECC_PARITY_SIZE_BYTES_BCH;

	host->ecc_buf_cfg = 0x203 << NUM_STEPS;

	host->clrflashstatus = FS_READY_BSY_N;
	host->clrreadstatus = 0xc0;
	nandc->regs->erased_cw_detect_cfg_clr =
		cpu_to_le32(CLR_ERASED_PAGE_DET);
	nandc->regs->erased_cw_detect_cfg_set =
		cpu_to_le32(SET_ERASED_PAGE_DET);

	dev_dbg(nandc->dev,
		"cfg0 %x cfg1 %x ecc_buf_cfg %x ecc_bch cfg %x cw_size %d cw_data %d strength %d parity_bytes %d steps %d\n",
		host->cfg0, host->cfg1, host->ecc_buf_cfg, host->ecc_bch_cfg,
		host->cw_size, host->cw_data, ecc->strength, ecc->bytes,
		cwperpage);

	return 0;
}

static int qcom_nandc_alloc(struct qcom_nand_controller *nandc)
{
	int ret;

	ret = dma_set_coherent_mask(nandc->dev, DMA_BIT_MASK(32));
	if (ret) {
		dev_err(nandc->dev, "failed to set DMA mask\n");
		return ret;
	}

	/*
	 * we use the internal buffer for reading ONFI params, reading small
	 * data like ID and status, and preforming read-copy-write operations
	 * when writing to a codeword partially. 532 is the maximum possible
	 * size of a codeword for our nand controller
	 */
	nandc->buf_size = 532;

	nandc->data_buffer = devm_kzalloc(nandc->dev, nandc->buf_size,
					GFP_KERNEL);
	if (!nandc->data_buffer)
		return -ENOMEM;

	nandc->regs = devm_kzalloc(nandc->dev, sizeof(*nandc->regs),
					GFP_KERNEL);
	if (!nandc->regs)
		return -ENOMEM;

	nandc->reg_read_buf = devm_kzalloc(nandc->dev,
				MAX_REG_RD * sizeof(*nandc->reg_read_buf),
				GFP_KERNEL);
	if (!nandc->reg_read_buf)
		return -ENOMEM;

	if (nandc->props->is_bam) {
		nandc->reg_read_dma =
			dma_map_single(nandc->dev, nandc->reg_read_buf,
				       MAX_REG_RD *
				       sizeof(*nandc->reg_read_buf),
				       DMA_FROM_DEVICE);
		if (dma_mapping_error(nandc->dev, nandc->reg_read_dma)) {
			dev_err(nandc->dev, "failed to DMA MAP reg buffer\n");
			return -EIO;
		}

		nandc->tx_chan = dma_request_slave_channel(nandc->dev, "tx");
		if (!nandc->tx_chan) {
			dev_err(nandc->dev, "failed to request tx channel\n");
			return -ENODEV;
		}

		nandc->rx_chan = dma_request_slave_channel(nandc->dev, "rx");
		if (!nandc->rx_chan) {
			dev_err(nandc->dev, "failed to request rx channel\n");
			return -ENODEV;
		}

		nandc->cmd_chan = dma_request_slave_channel(nandc->dev, "cmd");
		if (!nandc->cmd_chan) {
			dev_err(nandc->dev, "failed to request cmd channel\n");
			return -ENODEV;
		}

		/*
		 * Initially allocate BAM transaction to read ONFI param page.
		 * After detecting all the devices, this BAM transaction will
		 * be freed and the next BAM tranasction will be allocated with
		 * maximum codeword size
		 */
		nandc->max_cwperpage = 1;
		nandc->bam_txn = alloc_bam_transaction(nandc);
		if (!nandc->bam_txn) {
			dev_err(nandc->dev,
				"failed to allocate bam transaction\n");
			return -ENOMEM;
		}
	} else {
		nandc->chan = dma_request_slave_channel(nandc->dev, "rxtx");
		if (!nandc->chan) {
			dev_err(nandc->dev,
				"failed to request slave channel\n");
			return -ENODEV;
		}
	}

	INIT_LIST_HEAD(&nandc->desc_list);
	INIT_LIST_HEAD(&nandc->host_list);

	nand_hw_control_init(&nandc->controller);

	return 0;
}

static void qcom_nandc_unalloc(struct qcom_nand_controller *nandc)
{
	if (nandc->props->is_bam) {
		if (!dma_mapping_error(nandc->dev, nandc->reg_read_dma))
			dma_unmap_single(nandc->dev, nandc->reg_read_dma,
					 MAX_REG_RD *
					 sizeof(*nandc->reg_read_buf),
					 DMA_FROM_DEVICE);

		if (nandc->tx_chan)
			dma_release_channel(nandc->tx_chan);

		if (nandc->rx_chan)
			dma_release_channel(nandc->rx_chan);

		if (nandc->cmd_chan)
			dma_release_channel(nandc->cmd_chan);
	} else {
		if (nandc->chan)
			dma_release_channel(nandc->chan);
	}
}

/* one time setup of a few nand controller registers */
static int qcom_nandc_setup(struct qcom_nand_controller *nandc)
{
	u32 nand_ctrl;

	/* kill onenand */
	nandc_write(nandc, SFLASHC_BURST_CFG, 0);
	nandc_write(nandc, NAND_DEV_CMD_VLD, NAND_DEV_CMD_VLD_VAL);

	/* enable ADM or BAM DMA */
	if (nandc->props->is_bam) {
		nand_ctrl = nandc_read(nandc, NAND_CTRL);
		nandc_write(nandc, NAND_CTRL, nand_ctrl | BAM_MODE_EN);
	} else {
		nandc_write(nandc, NAND_FLASH_CHIP_SELECT, DM_EN);
	}

	/* save the original values of these registers */
	nandc->cmd1 = nandc_read(nandc, NAND_DEV_CMD1);
	nandc->vld = NAND_DEV_CMD_VLD_VAL;

	return 0;
}

static int qcom_nand_host_init(struct qcom_nand_controller *nandc,
			       struct qcom_nand_host *host,
			       struct device_node *dn)
{
	struct nand_chip *chip = &host->chip;
	struct mtd_info *mtd = nand_to_mtd(chip);
	struct device *dev = nandc->dev;
	int ret;

	ret = of_property_read_u32(dn, "reg", &host->cs);
	if (ret) {
		dev_err(dev, "can't get chip-select\n");
		return -ENXIO;
	}

	nand_set_flash_node(chip, dn);
	mtd->name = devm_kasprintf(dev, GFP_KERNEL, "qcom_nand.%d", host->cs);
	mtd->owner = THIS_MODULE;
	mtd->dev.parent = dev;

	chip->cmdfunc		= qcom_nandc_command;
	chip->select_chip	= qcom_nandc_select_chip;
	chip->read_byte		= qcom_nandc_read_byte;
	chip->read_buf		= qcom_nandc_read_buf;
	chip->write_buf		= qcom_nandc_write_buf;
	chip->onfi_set_features	= nand_onfi_get_set_features_notsupp;
	chip->onfi_get_features	= nand_onfi_get_set_features_notsupp;

	/*
	 * the bad block marker is readable only when we read the last codeword
	 * of a page with ECC disabled. currently, the nand_base and nand_bbt
	 * helpers don't allow us to read BB from a nand chip with ECC
	 * disabled (MTD_OPS_PLACE_OOB is set by default). use the block_bad
	 * and block_markbad helpers until we permanently switch to using
	 * MTD_OPS_RAW for all drivers (with the help of badblockbits)
	 */
	chip->block_bad		= qcom_nandc_block_bad;
	chip->block_markbad	= qcom_nandc_block_markbad;

	chip->controller = &nandc->controller;
	chip->options |= NAND_NO_SUBPAGE_WRITE | NAND_USE_BOUNCE_BUFFER |
			 NAND_SKIP_BBTSCAN;

	/* set up initial status value */
	host->status = NAND_STATUS_READY | NAND_STATUS_WP;

	ret = nand_scan_ident(mtd, 1, NULL);
	if (ret)
		return ret;

	ret = qcom_nand_host_setup(host);

	return ret;
}

static int qcom_nand_mtd_register(struct qcom_nand_controller *nandc,
				  struct qcom_nand_host *host,
				  struct device_node *dn)
{
	struct nand_chip *chip = &host->chip;
	struct mtd_info *mtd = nand_to_mtd(chip);
	int ret;

	ret = nand_scan_tail(mtd);
	if (ret)
		return ret;

	ret = mtd_device_register(mtd, NULL, 0);
	if (ret)
		nand_cleanup(mtd_to_nand(mtd));

	return ret;
}

static int qcom_probe_nand_devices(struct qcom_nand_controller *nandc)
{
	struct device *dev = nandc->dev;
	struct device_node *dn = dev->of_node, *child;
	struct qcom_nand_host *host, *tmp;
	int ret;

	for_each_available_child_of_node(dn, child) {
		host = devm_kzalloc(dev, sizeof(*host), GFP_KERNEL);
		if (!host) {
			of_node_put(child);
			return -ENOMEM;
		}

		ret = qcom_nand_host_init(nandc, host, child);
		if (ret) {
			devm_kfree(dev, host);
			continue;
		}

		list_add_tail(&host->node, &nandc->host_list);
	}

	if (list_empty(&nandc->host_list))
		return -ENODEV;

	if (nandc->props->is_bam) {
		free_bam_transaction(nandc);
		nandc->bam_txn = alloc_bam_transaction(nandc);
		if (!nandc->bam_txn) {
			dev_err(nandc->dev,
				"failed to allocate bam transaction\n");
			return -ENOMEM;
		}
	}

	list_for_each_entry_safe(host, tmp, &nandc->host_list, node) {
		ret = qcom_nand_mtd_register(nandc, host, child);
		if (ret) {
			list_del(&host->node);
			devm_kfree(dev, host);
		}
	}

	if (list_empty(&nandc->host_list))
		return -ENODEV;

	return 0;
}

/* parse custom DT properties here */
static int qcom_nandc_parse_dt(struct platform_device *pdev)
{
	struct qcom_nand_controller *nandc = platform_get_drvdata(pdev);
	struct device_node *np = nandc->dev->of_node;
	int ret;

	if (!nandc->props->is_bam) {
		ret = of_property_read_u32(np, "qcom,cmd-crci",
					   &nandc->cmd_crci);
		if (ret) {
			dev_err(nandc->dev, "command CRCI unspecified\n");
			return ret;
		}

		ret = of_property_read_u32(np, "qcom,data-crci",
					   &nandc->data_crci);
		if (ret) {
			dev_err(nandc->dev, "data CRCI unspecified\n");
			return ret;
		}
	}

	return 0;
}

static int qcom_nandc_probe(struct platform_device *pdev)
{
	struct qcom_nand_controller *nandc;
	const void *dev_data;
	struct device *dev = &pdev->dev;
	struct resource *res;
	int ret;

	nandc = devm_kzalloc(&pdev->dev, sizeof(*nandc), GFP_KERNEL);
	if (!nandc)
		return -ENOMEM;

	platform_set_drvdata(pdev, nandc);
	nandc->dev = dev;

	dev_data = of_device_get_match_data(dev);
	if (!dev_data) {
		dev_err(&pdev->dev, "failed to get device data\n");
		return -ENODEV;
	}

	nandc->props = dev_data;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	nandc->base = devm_ioremap_resource(dev, res);
	if (IS_ERR(nandc->base))
		return PTR_ERR(nandc->base);

	nandc->base_dma = phys_to_dma(dev, (phys_addr_t)res->start);

	nandc->core_clk = devm_clk_get(dev, "core");
	if (IS_ERR(nandc->core_clk))
		return PTR_ERR(nandc->core_clk);

	nandc->aon_clk = devm_clk_get(dev, "aon");
	if (IS_ERR(nandc->aon_clk))
		return PTR_ERR(nandc->aon_clk);

	ret = qcom_nandc_parse_dt(pdev);
	if (ret)
		return ret;

	ret = qcom_nandc_alloc(nandc);
	if (ret)
		goto err_core_clk;

	ret = clk_prepare_enable(nandc->core_clk);
	if (ret)
		goto err_core_clk;

	ret = clk_prepare_enable(nandc->aon_clk);
	if (ret)
		goto err_aon_clk;

	ret = qcom_nandc_setup(nandc);
	if (ret)
		goto err_setup;

	ret = qcom_probe_nand_devices(nandc);
	if (ret)
		goto err_setup;

	return 0;

err_setup:
	clk_disable_unprepare(nandc->aon_clk);
err_aon_clk:
	clk_disable_unprepare(nandc->core_clk);
err_core_clk:
	qcom_nandc_unalloc(nandc);

	return ret;
}

static int qcom_nandc_remove(struct platform_device *pdev)
{
	struct qcom_nand_controller *nandc = platform_get_drvdata(pdev);
	struct qcom_nand_host *host;

	list_for_each_entry(host, &nandc->host_list, node)
		nand_release(nand_to_mtd(&host->chip));

	qcom_nandc_unalloc(nandc);

	clk_disable_unprepare(nandc->aon_clk);
	clk_disable_unprepare(nandc->core_clk);

	return 0;
}

static const struct qcom_nandc_props ipq806x_nandc_props = {
	.ecc_modes = (ECC_RS_4BIT | ECC_BCH_8BIT),
	.is_bam = false,
};

/*
 * data will hold a struct pointer containing more differences once we support
 * more controller variants
 */
static const struct of_device_id qcom_nandc_of_match[] = {
	{
		.compatible = "qcom,ipq806x-nand",
		.data = &ipq806x_nandc_props,
	},
	{}
};
MODULE_DEVICE_TABLE(of, qcom_nandc_of_match);

static struct platform_driver qcom_nandc_driver = {
	.driver = {
		.name = "qcom-nandc",
		.of_match_table = qcom_nandc_of_match,
	},
	.probe   = qcom_nandc_probe,
	.remove  = qcom_nandc_remove,
};
module_platform_driver(qcom_nandc_driver);

MODULE_AUTHOR("Archit Taneja <architt@codeaurora.org>");
MODULE_DESCRIPTION("Qualcomm NAND Controller driver");
MODULE_LICENSE("GPL v2");