drivers/spi/spi-mtk-snfi.c

// SPDX-License-Identifier: GPL-2.0
//
// Driver for the SPI-NAND mode of Mediatek NAND Flash Interface
//
// Copyright (c) 2022 Chuanhong Guo <gch981213@gmail.com>
//
// This driver is based on the SPI-NAND mtd driver from Mediatek SDK:
//
// Copyright (C) 2020 MediaTek Inc.
// Author: Weijie Gao <weijie.gao@mediatek.com>
//
// This controller organize the page data as several interleaved sectors
// like the following: (sizeof(FDM + ECC) = snf->nfi_cfg.spare_size)
// +---------+------+------+---------+------+------+-----+
// | Sector1 | FDM1 | ECC1 | Sector2 | FDM2 | ECC2 | ... |
// +---------+------+------+---------+------+------+-----+
// With auto-format turned on, DMA only returns this part:
// +---------+---------+-----+
// | Sector1 | Sector2 | ... |
// +---------+---------+-----+
// The FDM data will be filled to the registers, and ECC parity data isn't
// accessible.
// With auto-format off, all ((Sector+FDM+ECC)*nsectors) will be read over DMA
// in it's original order shown in the first table. ECC can't be turned on when
// auto-format is off.
//
// However, Linux SPI-NAND driver expects the data returned as:
// +------+-----+
// | Page | OOB |
// +------+-----+
// where the page data is continuously stored instead of interleaved.
// So we assume all instructions matching the page_op template between ECC
// prepare_io_req and finish_io_req are for page cache r/w.
// Here's how this spi-mem driver operates when reading:
//  1. Always set snf->autofmt = true in prepare_io_req (even when ECC is off).
//  2. Perform page ops and let the controller fill the DMA bounce buffer with
//     de-interleaved sector data and set FDM registers.
//  3. Return the data as:
//     +---------+---------+-----+------+------+-----+
//     | Sector1 | Sector2 | ... | FDM1 | FDM2 | ... |
//     +---------+---------+-----+------+------+-----+
//  4. For other matching spi_mem ops outside a prepare/finish_io_req pair,
//     read the data with auto-format off into the bounce buffer and copy
//     needed data to the buffer specified in the request.
//
// Write requests operates in a similar manner.
// As a limitation of this strategy, we won't be able to access any ECC parity
// data at all in Linux.
//
// Here's the bad block mark situation on MTK chips:
// In older chips like mt7622, MTK uses the first FDM byte in the first sector
// as the bad block mark. After de-interleaving, this byte appears at [pagesize]
// in the returned data, which is the BBM position expected by kernel. However,
// the conventional bad block mark is the first byte of the OOB, which is part
// of the last sector data in the interleaved layout. Instead of fixing their
// hardware, MTK decided to address this inconsistency in software. On these
// later chips, the BootROM expects the following:
// 1. The [pagesize] byte on a nand page is used as BBM, which will appear at
//    (page_size - (nsectors - 1) * spare_size) in the DMA buffer.
// 2. The original byte stored at that position in the DMA buffer will be stored
//    as the first byte of the FDM section in the last sector.
// We can't disagree with the BootROM, so after de-interleaving, we need to
// perform the following swaps in read:
// 1. Store the BBM at [page_size - (nsectors - 1) * spare_size] to [page_size],
//    which is the expected BBM position by kernel.
// 2. Store the page data byte at [pagesize + (nsectors-1) * fdm] back to
//    [page_size - (nsectors - 1) * spare_size]
// Similarly, when writing, we need to perform swaps in the other direction.

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/mutex.h>
#include <linux/clk.h>
#include <linux/interrupt.h>
#include <linux/dma-mapping.h>
#include <linux/iopoll.h>
#include <linux/of_platform.h>
#include <linux/mtd/nand-ecc-mtk.h>
#include <linux/spi/spi.h>
#include <linux/spi/spi-mem.h>
#include <linux/mtd/nand.h>

// NFI registers
#define NFI_CNFG 0x000
#define CNFG_OP_MODE_S 12
#define CNFG_OP_MODE_CUST 6
#define CNFG_OP_MODE_PROGRAM 3
#define CNFG_AUTO_FMT_EN BIT(9)
#define CNFG_HW_ECC_EN BIT(8)
#define CNFG_DMA_BURST_EN BIT(2)
#define CNFG_READ_MODE BIT(1)
#define CNFG_DMA_MODE BIT(0)

#define NFI_PAGEFMT 0x0004
#define NFI_SPARE_SIZE_LS_S 16
#define NFI_FDM_ECC_NUM_S 12
#define NFI_FDM_NUM_S 8
#define NFI_SPARE_SIZE_S 4
#define NFI_SEC_SEL_512 BIT(2)
#define NFI_PAGE_SIZE_S 0
#define NFI_PAGE_SIZE_512_2K 0
#define NFI_PAGE_SIZE_2K_4K 1
#define NFI_PAGE_SIZE_4K_8K 2
#define NFI_PAGE_SIZE_8K_16K 3

#define NFI_CON 0x008
#define CON_SEC_NUM_S 12
#define CON_BWR BIT(9)
#define CON_BRD BIT(8)
#define CON_NFI_RST BIT(1)
#define CON_FIFO_FLUSH BIT(0)

#define NFI_INTR_EN 0x010
#define NFI_INTR_STA 0x014
#define NFI_IRQ_INTR_EN BIT(31)
#define NFI_IRQ_CUS_READ BIT(8)
#define NFI_IRQ_CUS_PG BIT(7)

#define NFI_CMD 0x020
#define NFI_CMD_DUMMY_READ 0x00
#define NFI_CMD_DUMMY_WRITE 0x80

#define NFI_STRDATA 0x040
#define STR_DATA BIT(0)

#define NFI_STA 0x060
#define NFI_NAND_FSM GENMASK(28, 24)
#define NFI_FSM GENMASK(19, 16)
#define READ_EMPTY BIT(12)

#define NFI_FIFOSTA 0x064
#define FIFO_WR_REMAIN_S 8
#define FIFO_RD_REMAIN_S 0

#define NFI_ADDRCNTR 0x070
#define SEC_CNTR GENMASK(16, 12)
#define SEC_CNTR_S 12
#define NFI_SEC_CNTR(val) (((val)&SEC_CNTR) >> SEC_CNTR_S)

#define NFI_STRADDR 0x080

#define NFI_BYTELEN 0x084
#define BUS_SEC_CNTR(val) (((val)&SEC_CNTR) >> SEC_CNTR_S)

#define NFI_FDM0L 0x0a0
#define NFI_FDM0M 0x0a4
#define NFI_FDML(n) (NFI_FDM0L + (n)*8)
#define NFI_FDMM(n) (NFI_FDM0M + (n)*8)

#define NFI_DEBUG_CON1 0x220
#define WBUF_EN BIT(2)

#define NFI_MASTERSTA 0x224
#define MAS_ADDR GENMASK(11, 9)
#define MAS_RD GENMASK(8, 6)
#define MAS_WR GENMASK(5, 3)
#define MAS_RDDLY GENMASK(2, 0)
#define NFI_MASTERSTA_MASK_7622 (MAS_ADDR | MAS_RD | MAS_WR | MAS_RDDLY)

// SNFI registers
#define SNF_MAC_CTL 0x500
#define MAC_XIO_SEL BIT(4)
#define SF_MAC_EN BIT(3)
#define SF_TRIG BIT(2)
#define WIP_READY BIT(1)
#define WIP BIT(0)

#define SNF_MAC_OUTL 0x504
#define SNF_MAC_INL 0x508

#define SNF_RD_CTL2 0x510
#define DATA_READ_DUMMY_S 8
#define DATA_READ_MAX_DUMMY 0xf
#define DATA_READ_CMD_S 0

#define SNF_RD_CTL3 0x514

#define SNF_PG_CTL1 0x524
#define PG_LOAD_CMD_S 8

#define SNF_PG_CTL2 0x528

#define SNF_MISC_CTL 0x538
#define SW_RST BIT(28)
#define FIFO_RD_LTC_S 25
#define PG_LOAD_X4_EN BIT(20)
#define DATA_READ_MODE_S 16
#define DATA_READ_MODE GENMASK(18, 16)
#define DATA_READ_MODE_X1 0
#define DATA_READ_MODE_X2 1
#define DATA_READ_MODE_X4 2
#define DATA_READ_MODE_DUAL 5
#define DATA_READ_MODE_QUAD 6
#define PG_LOAD_CUSTOM_EN BIT(7)
#define DATARD_CUSTOM_EN BIT(6)
#define CS_DESELECT_CYC_S 0

#define SNF_MISC_CTL2 0x53c
#define PROGRAM_LOAD_BYTE_NUM_S 16
#define READ_DATA_BYTE_NUM_S 11

#define SNF_DLY_CTL3 0x548
#define SFCK_SAM_DLY_S 0

#define SNF_STA_CTL1 0x550
#define CUS_PG_DONE BIT(28)
#define CUS_READ_DONE BIT(27)
#define SPI_STATE_S 0
#define SPI_STATE GENMASK(3, 0)

#define SNF_CFG 0x55c
#define SPI_MODE BIT(0)

#define SNF_GPRAM 0x800
#define SNF_GPRAM_SIZE 0xa0

#define SNFI_POLL_INTERVAL 1000000

static const u8 mt7622_spare_sizes[] = { 16, 26, 27, 28 };

struct mtk_snand_caps {
	u16 sector_size;
	u16 max_sectors;
	u16 fdm_size;
	u16 fdm_ecc_size;
	u16 fifo_size;

	bool bbm_swap;
	bool empty_page_check;
	u32 mastersta_mask;

	const u8 *spare_sizes;
	u32 num_spare_size;
};

static const struct mtk_snand_caps mt7622_snand_caps = {
	.sector_size = 512,
	.max_sectors = 8,
	.fdm_size = 8,
	.fdm_ecc_size = 1,
	.fifo_size = 32,
	.bbm_swap = false,
	.empty_page_check = false,
	.mastersta_mask = NFI_MASTERSTA_MASK_7622,
	.spare_sizes = mt7622_spare_sizes,
	.num_spare_size = ARRAY_SIZE(mt7622_spare_sizes)
};

static const struct mtk_snand_caps mt7629_snand_caps = {
	.sector_size = 512,
	.max_sectors = 8,
	.fdm_size = 8,
	.fdm_ecc_size = 1,
	.fifo_size = 32,
	.bbm_swap = true,
	.empty_page_check = false,
	.mastersta_mask = NFI_MASTERSTA_MASK_7622,
	.spare_sizes = mt7622_spare_sizes,
	.num_spare_size = ARRAY_SIZE(mt7622_spare_sizes)
};

struct mtk_snand_conf {
	size_t page_size;
	size_t oob_size;
	u8 nsectors;
	u8 spare_size;
};

struct mtk_snand {
	struct spi_controller *ctlr;
	struct device *dev;
	struct clk *nfi_clk;
	struct clk *pad_clk;
	void __iomem *nfi_base;
	int irq;
	struct completion op_done;
	const struct mtk_snand_caps *caps;
	struct mtk_ecc_config *ecc_cfg;
	struct mtk_ecc *ecc;
	struct mtk_snand_conf nfi_cfg;
	struct mtk_ecc_stats ecc_stats;
	struct nand_ecc_engine ecc_eng;
	bool autofmt;
	u8 *buf;
	size_t buf_len;
};

static struct mtk_snand *nand_to_mtk_snand(struct nand_device *nand)
{
	struct nand_ecc_engine *eng = nand->ecc.engine;

	return container_of(eng, struct mtk_snand, ecc_eng);
}

static inline int snand_prepare_bouncebuf(struct mtk_snand *snf, size_t size)
{
	if (snf->buf_len >= size)
		return 0;
	kfree(snf->buf);
	snf->buf = kmalloc(size, GFP_KERNEL);
	if (!snf->buf)
		return -ENOMEM;
	snf->buf_len = size;
	memset(snf->buf, 0xff, snf->buf_len);
	return 0;
}

static inline u32 nfi_read32(struct mtk_snand *snf, u32 reg)
{
	return readl(snf->nfi_base + reg);
}

static inline void nfi_write32(struct mtk_snand *snf, u32 reg, u32 val)
{
	writel(val, snf->nfi_base + reg);
}

static inline void nfi_write16(struct mtk_snand *snf, u32 reg, u16 val)
{
	writew(val, snf->nfi_base + reg);
}

static inline void nfi_rmw32(struct mtk_snand *snf, u32 reg, u32 clr, u32 set)
{
	u32 val;

	val = readl(snf->nfi_base + reg);
	val &= ~clr;
	val |= set;
	writel(val, snf->nfi_base + reg);
}

static void nfi_read_data(struct mtk_snand *snf, u32 reg, u8 *data, u32 len)
{
	u32 i, val = 0, es = sizeof(u32);

	for (i = reg; i < reg + len; i++) {
		if (i == reg || i % es == 0)
			val = nfi_read32(snf, i & ~(es - 1));

		*data++ = (u8)(val >> (8 * (i % es)));
	}
}

static int mtk_nfi_reset(struct mtk_snand *snf)
{
	u32 val, fifo_mask;
	int ret;

	nfi_write32(snf, NFI_CON, CON_FIFO_FLUSH | CON_NFI_RST);

	ret = readw_poll_timeout(snf->nfi_base + NFI_MASTERSTA, val,
				 !(val & snf->caps->mastersta_mask), 0,
				 SNFI_POLL_INTERVAL);
	if (ret) {
		dev_err(snf->dev, "NFI master is still busy after reset\n");
		return ret;
	}

	ret = readl_poll_timeout(snf->nfi_base + NFI_STA, val,
				 !(val & (NFI_FSM | NFI_NAND_FSM)), 0,
				 SNFI_POLL_INTERVAL);
	if (ret) {
		dev_err(snf->dev, "Failed to reset NFI\n");
		return ret;
	}

	fifo_mask = ((snf->caps->fifo_size - 1) << FIFO_RD_REMAIN_S) |
		    ((snf->caps->fifo_size - 1) << FIFO_WR_REMAIN_S);
	ret = readw_poll_timeout(snf->nfi_base + NFI_FIFOSTA, val,
				 !(val & fifo_mask), 0, SNFI_POLL_INTERVAL);
	if (ret) {
		dev_err(snf->dev, "NFI FIFOs are not empty\n");
		return ret;
	}

	return 0;
}

static int mtk_snand_mac_reset(struct mtk_snand *snf)
{
	int ret;
	u32 val;

	nfi_rmw32(snf, SNF_MISC_CTL, 0, SW_RST);

	ret = readl_poll_timeout(snf->nfi_base + SNF_STA_CTL1, val,
				 !(val & SPI_STATE), 0, SNFI_POLL_INTERVAL);
	if (ret)
		dev_err(snf->dev, "Failed to reset SNFI MAC\n");

	nfi_write32(snf, SNF_MISC_CTL,
		    (2 << FIFO_RD_LTC_S) | (10 << CS_DESELECT_CYC_S));

	return ret;
}

static int mtk_snand_mac_trigger(struct mtk_snand *snf, u32 outlen, u32 inlen)
{
	int ret;
	u32 val;

	nfi_write32(snf, SNF_MAC_CTL, SF_MAC_EN);
	nfi_write32(snf, SNF_MAC_OUTL, outlen);
	nfi_write32(snf, SNF_MAC_INL, inlen);

	nfi_write32(snf, SNF_MAC_CTL, SF_MAC_EN | SF_TRIG);

	ret = readl_poll_timeout(snf->nfi_base + SNF_MAC_CTL, val,
				 val & WIP_READY, 0, SNFI_POLL_INTERVAL);
	if (ret) {
		dev_err(snf->dev, "Timed out waiting for WIP_READY\n");
		goto cleanup;
	}

	ret = readl_poll_timeout(snf->nfi_base + SNF_MAC_CTL, val, !(val & WIP),
				 0, SNFI_POLL_INTERVAL);
	if (ret)
		dev_err(snf->dev, "Timed out waiting for WIP cleared\n");

cleanup:
	nfi_write32(snf, SNF_MAC_CTL, 0);

	return ret;
}

static int mtk_snand_mac_io(struct mtk_snand *snf, const struct spi_mem_op *op)
{
	u32 rx_len = 0;
	u32 reg_offs = 0;
	u32 val = 0;
	const u8 *tx_buf = NULL;
	u8 *rx_buf = NULL;
	int i, ret;
	u8 b;

	if (op->data.dir == SPI_MEM_DATA_IN) {
		rx_len = op->data.nbytes;
		rx_buf = op->data.buf.in;
	} else {
		tx_buf = op->data.buf.out;
	}

	mtk_snand_mac_reset(snf);

	for (i = 0; i < op->cmd.nbytes; i++, reg_offs++) {
		b = (op->cmd.opcode >> ((op->cmd.nbytes - i - 1) * 8)) & 0xff;
		val |= b << (8 * (reg_offs % 4));
		if (reg_offs % 4 == 3) {
			nfi_write32(snf, SNF_GPRAM + reg_offs - 3, val);
			val = 0;
		}
	}

	for (i = 0; i < op->addr.nbytes; i++, reg_offs++) {
		b = (op->addr.val >> ((op->addr.nbytes - i - 1) * 8)) & 0xff;
		val |= b << (8 * (reg_offs % 4));
		if (reg_offs % 4 == 3) {
			nfi_write32(snf, SNF_GPRAM + reg_offs - 3, val);
			val = 0;
		}
	}

	for (i = 0; i < op->dummy.nbytes; i++, reg_offs++) {
		if (reg_offs % 4 == 3) {
			nfi_write32(snf, SNF_GPRAM + reg_offs - 3, val);
			val = 0;
		}
	}

	if (op->data.dir == SPI_MEM_DATA_OUT) {
		for (i = 0; i < op->data.nbytes; i++, reg_offs++) {
			val |= tx_buf[i] << (8 * (reg_offs % 4));
			if (reg_offs % 4 == 3) {
				nfi_write32(snf, SNF_GPRAM + reg_offs - 3, val);
				val = 0;
			}
		}
	}

	if (reg_offs % 4)
		nfi_write32(snf, SNF_GPRAM + (reg_offs & ~3), val);

	for (i = 0; i < reg_offs; i += 4)
		dev_dbg(snf->dev, "%d: %08X", i,
			nfi_read32(snf, SNF_GPRAM + i));

	dev_dbg(snf->dev, "SNF TX: %u RX: %u", reg_offs, rx_len);

	ret = mtk_snand_mac_trigger(snf, reg_offs, rx_len);
	if (ret)
		return ret;

	if (!rx_len)
		return 0;

	nfi_read_data(snf, SNF_GPRAM + reg_offs, rx_buf, rx_len);
	return 0;
}

static int mtk_snand_setup_pagefmt(struct mtk_snand *snf, u32 page_size,
				   u32 oob_size)
{
	int spare_idx = -1;
	u32 spare_size, spare_size_shift, pagesize_idx;
	u32 sector_size_512;
	u8 nsectors;
	int i;

	// skip if it's already configured as required.
	if (snf->nfi_cfg.page_size == page_size &&
	    snf->nfi_cfg.oob_size == oob_size)
		return 0;

	nsectors = page_size / snf->caps->sector_size;
	if (nsectors > snf->caps->max_sectors) {
		dev_err(snf->dev, "too many sectors required.\n");
		goto err;
	}

	if (snf->caps->sector_size == 512) {
		sector_size_512 = NFI_SEC_SEL_512;
		spare_size_shift = NFI_SPARE_SIZE_S;
	} else {
		sector_size_512 = 0;
		spare_size_shift = NFI_SPARE_SIZE_LS_S;
	}

	switch (page_size) {
	case SZ_512:
		pagesize_idx = NFI_PAGE_SIZE_512_2K;
		break;
	case SZ_2K:
		if (snf->caps->sector_size == 512)
			pagesize_idx = NFI_PAGE_SIZE_2K_4K;
		else
			pagesize_idx = NFI_PAGE_SIZE_512_2K;
		break;
	case SZ_4K:
		if (snf->caps->sector_size == 512)
			pagesize_idx = NFI_PAGE_SIZE_4K_8K;
		else
			pagesize_idx = NFI_PAGE_SIZE_2K_4K;
		break;
	case SZ_8K:
		if (snf->caps->sector_size == 512)
			pagesize_idx = NFI_PAGE_SIZE_8K_16K;
		else
			pagesize_idx = NFI_PAGE_SIZE_4K_8K;
		break;
	case SZ_16K:
		pagesize_idx = NFI_PAGE_SIZE_8K_16K;
		break;
	default:
		dev_err(snf->dev, "unsupported page size.\n");
		goto err;
	}

	spare_size = oob_size / nsectors;
	// If we're using the 1KB sector size, HW will automatically double the
	// spare size. We should only use half of the value in this case.
	if (snf->caps->sector_size == 1024)
		spare_size /= 2;

	for (i = snf->caps->num_spare_size - 1; i >= 0; i--) {
		if (snf->caps->spare_sizes[i] <= spare_size) {
			spare_size = snf->caps->spare_sizes[i];
			if (snf->caps->sector_size == 1024)
				spare_size *= 2;
			spare_idx = i;
			break;
		}
	}

	if (spare_idx < 0) {
		dev_err(snf->dev, "unsupported spare size: %u\n", spare_size);
		goto err;
	}

	nfi_write32(snf, NFI_PAGEFMT,
		    (snf->caps->fdm_ecc_size << NFI_FDM_ECC_NUM_S) |
			    (snf->caps->fdm_size << NFI_FDM_NUM_S) |
			    (spare_idx << spare_size_shift) |
			    (pagesize_idx << NFI_PAGE_SIZE_S) |
			    sector_size_512);

	snf->nfi_cfg.page_size = page_size;
	snf->nfi_cfg.oob_size = oob_size;
	snf->nfi_cfg.nsectors = nsectors;
	snf->nfi_cfg.spare_size = spare_size;

	dev_dbg(snf->dev, "page format: (%u + %u) * %u\n",
		snf->caps->sector_size, spare_size, nsectors);
	return snand_prepare_bouncebuf(snf, page_size + oob_size);
err:
	dev_err(snf->dev, "page size %u + %u is not supported\n", page_size,
		oob_size);
	return -EOPNOTSUPP;
}

static int mtk_snand_ooblayout_ecc(struct mtd_info *mtd, int section,
				   struct mtd_oob_region *oobecc)
{
	// ECC area is not accessible
	return -ERANGE;
}

static int mtk_snand_ooblayout_free(struct mtd_info *mtd, int section,
				    struct mtd_oob_region *oobfree)
{
	struct nand_device *nand = mtd_to_nanddev(mtd);
	struct mtk_snand *ms = nand_to_mtk_snand(nand);

	if (section >= ms->nfi_cfg.nsectors)
		return -ERANGE;

	oobfree->length = ms->caps->fdm_size - 1;
	oobfree->offset = section * ms->caps->fdm_size + 1;
	return 0;
}

static const struct mtd_ooblayout_ops mtk_snand_ooblayout = {
	.ecc = mtk_snand_ooblayout_ecc,
	.free = mtk_snand_ooblayout_free,
};

static int mtk_snand_ecc_init_ctx(struct nand_device *nand)
{
	struct mtk_snand *snf = nand_to_mtk_snand(nand);
	struct nand_ecc_props *conf = &nand->ecc.ctx.conf;
	struct nand_ecc_props *reqs = &nand->ecc.requirements;
	struct nand_ecc_props *user = &nand->ecc.user_conf;
	struct mtd_info *mtd = nanddev_to_mtd(nand);
	int step_size = 0, strength = 0, desired_correction = 0, steps;
	bool ecc_user = false;
	int ret;
	u32 parity_bits, max_ecc_bytes;
	struct mtk_ecc_config *ecc_cfg;

	ret = mtk_snand_setup_pagefmt(snf, nand->memorg.pagesize,
				      nand->memorg.oobsize);
	if (ret)
		return ret;

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

	nand->ecc.ctx.priv = ecc_cfg;

	if (user->step_size && user->strength) {
		step_size = user->step_size;
		strength = user->strength;
		ecc_user = true;
	} else if (reqs->step_size && reqs->strength) {
		step_size = reqs->step_size;
		strength = reqs->strength;
	}

	if (step_size && strength) {
		steps = mtd->writesize / step_size;
		desired_correction = steps * strength;
		strength = desired_correction / snf->nfi_cfg.nsectors;
	}

	ecc_cfg->mode = ECC_NFI_MODE;
	ecc_cfg->sectors = snf->nfi_cfg.nsectors;
	ecc_cfg->len = snf->caps->sector_size + snf->caps->fdm_ecc_size;

	// calculate the max possible strength under current page format
	parity_bits = mtk_ecc_get_parity_bits(snf->ecc);
	max_ecc_bytes = snf->nfi_cfg.spare_size - snf->caps->fdm_size;
	ecc_cfg->strength = max_ecc_bytes * 8 / parity_bits;
	mtk_ecc_adjust_strength(snf->ecc, &ecc_cfg->strength);

	// if there's a user requested strength, find the minimum strength that
	// meets the requirement. Otherwise use the maximum strength which is
	// expected by BootROM.
	if (ecc_user && strength) {
		u32 s_next = ecc_cfg->strength - 1;

		while (1) {
			mtk_ecc_adjust_strength(snf->ecc, &s_next);
			if (s_next >= ecc_cfg->strength)
				break;
			if (s_next < strength)
				break;
			s_next = ecc_cfg->strength - 1;
		}
	}

	mtd_set_ooblayout(mtd, &mtk_snand_ooblayout);

	conf->step_size = snf->caps->sector_size;
	conf->strength = ecc_cfg->strength;

	if (ecc_cfg->strength < strength)
		dev_warn(snf->dev, "unable to fulfill ECC of %u bits.\n",
			 strength);
	dev_info(snf->dev, "ECC strength: %u bits per %u bytes\n",
		 ecc_cfg->strength, snf->caps->sector_size);

	return 0;
}

static void mtk_snand_ecc_cleanup_ctx(struct nand_device *nand)
{
	struct mtk_ecc_config *ecc_cfg = nand_to_ecc_ctx(nand);

	kfree(ecc_cfg);
}

static int mtk_snand_ecc_prepare_io_req(struct nand_device *nand,
					struct nand_page_io_req *req)
{
	struct mtk_snand *snf = nand_to_mtk_snand(nand);
	struct mtk_ecc_config *ecc_cfg = nand_to_ecc_ctx(nand);
	int ret;

	ret = mtk_snand_setup_pagefmt(snf, nand->memorg.pagesize,
				      nand->memorg.oobsize);
	if (ret)
		return ret;
	snf->autofmt = true;
	snf->ecc_cfg = ecc_cfg;
	return 0;
}

static int mtk_snand_ecc_finish_io_req(struct nand_device *nand,
				       struct nand_page_io_req *req)
{
	struct mtk_snand *snf = nand_to_mtk_snand(nand);
	struct mtd_info *mtd = nanddev_to_mtd(nand);

	snf->ecc_cfg = NULL;
	snf->autofmt = false;
	if ((req->mode == MTD_OPS_RAW) || (req->type != NAND_PAGE_READ))
		return 0;

	if (snf->ecc_stats.failed)
		mtd->ecc_stats.failed += snf->ecc_stats.failed;
	mtd->ecc_stats.corrected += snf->ecc_stats.corrected;
	return snf->ecc_stats.failed ? -EBADMSG : snf->ecc_stats.bitflips;
}

static struct nand_ecc_engine_ops mtk_snfi_ecc_engine_ops = {
	.init_ctx = mtk_snand_ecc_init_ctx,
	.cleanup_ctx = mtk_snand_ecc_cleanup_ctx,
	.prepare_io_req = mtk_snand_ecc_prepare_io_req,
	.finish_io_req = mtk_snand_ecc_finish_io_req,
};

static void mtk_snand_read_fdm(struct mtk_snand *snf, u8 *buf)
{
	u32 vall, valm;
	u8 *oobptr = buf;
	int i, j;

	for (i = 0; i < snf->nfi_cfg.nsectors; i++) {
		vall = nfi_read32(snf, NFI_FDML(i));
		valm = nfi_read32(snf, NFI_FDMM(i));

		for (j = 0; j < snf->caps->fdm_size; j++)
			oobptr[j] = (j >= 4 ? valm : vall) >> ((j % 4) * 8);

		oobptr += snf->caps->fdm_size;
	}
}

static void mtk_snand_write_fdm(struct mtk_snand *snf, const u8 *buf)
{
	u32 fdm_size = snf->caps->fdm_size;
	const u8 *oobptr = buf;
	u32 vall, valm;
	int i, j;

	for (i = 0; i < snf->nfi_cfg.nsectors; i++) {
		vall = 0;
		valm = 0;

		for (j = 0; j < 8; j++) {
			if (j < 4)
				vall |= (j < fdm_size ? oobptr[j] : 0xff)
					<< (j * 8);
			else
				valm |= (j < fdm_size ? oobptr[j] : 0xff)
					<< ((j - 4) * 8);
		}

		nfi_write32(snf, NFI_FDML(i), vall);
		nfi_write32(snf, NFI_FDMM(i), valm);

		oobptr += fdm_size;
	}
}

static void mtk_snand_bm_swap(struct mtk_snand *snf, u8 *buf)
{
	u32 buf_bbm_pos, fdm_bbm_pos;

	if (!snf->caps->bbm_swap || snf->nfi_cfg.nsectors == 1)
		return;

	// swap [pagesize] byte on nand with the first fdm byte
	// in the last sector.
	buf_bbm_pos = snf->nfi_cfg.page_size -
		      (snf->nfi_cfg.nsectors - 1) * snf->nfi_cfg.spare_size;
	fdm_bbm_pos = snf->nfi_cfg.page_size +
		      (snf->nfi_cfg.nsectors - 1) * snf->caps->fdm_size;

	swap(snf->buf[fdm_bbm_pos], buf[buf_bbm_pos]);
}

static void mtk_snand_fdm_bm_swap(struct mtk_snand *snf)
{
	u32 fdm_bbm_pos1, fdm_bbm_pos2;

	if (!snf->caps->bbm_swap || snf->nfi_cfg.nsectors == 1)
		return;

	// swap the first fdm byte in the first and the last sector.
	fdm_bbm_pos1 = snf->nfi_cfg.page_size;
	fdm_bbm_pos2 = snf->nfi_cfg.page_size +
		       (snf->nfi_cfg.nsectors - 1) * snf->caps->fdm_size;
	swap(snf->buf[fdm_bbm_pos1], snf->buf[fdm_bbm_pos2]);
}

static int mtk_snand_read_page_cache(struct mtk_snand *snf,
				     const struct spi_mem_op *op)
{
	u8 *buf = snf->buf;
	u8 *buf_fdm = buf + snf->nfi_cfg.page_size;
	// the address part to be sent by the controller
	u32 op_addr = op->addr.val;
	// where to start copying data from bounce buffer
	u32 rd_offset = 0;
	u32 dummy_clk = (op->dummy.nbytes * BITS_PER_BYTE / op->dummy.buswidth);
	u32 op_mode = 0;
	u32 dma_len = snf->buf_len;
	int ret = 0;
	u32 rd_mode, rd_bytes, val;
	dma_addr_t buf_dma;

	if (snf->autofmt) {
		u32 last_bit;
		u32 mask;

		dma_len = snf->nfi_cfg.page_size;
		op_mode = CNFG_AUTO_FMT_EN;
		if (op->data.ecc)
			op_mode |= CNFG_HW_ECC_EN;
		// extract the plane bit:
		// Find the highest bit set in (pagesize+oobsize).
		// Bits higher than that in op->addr are kept and sent over SPI
		// Lower bits are used as an offset for copying data from DMA
		// bounce buffer.
		last_bit = fls(snf->nfi_cfg.page_size + snf->nfi_cfg.oob_size);
		mask = (1 << last_bit) - 1;
		rd_offset = op_addr & mask;
		op_addr &= ~mask;

		// check if we can dma to the caller memory
		if (rd_offset == 0 && op->data.nbytes >= snf->nfi_cfg.page_size)
			buf = op->data.buf.in;
	}
	mtk_snand_mac_reset(snf);
	mtk_nfi_reset(snf);

	// command and dummy cycles
	nfi_write32(snf, SNF_RD_CTL2,
		    (dummy_clk << DATA_READ_DUMMY_S) |
			    (op->cmd.opcode << DATA_READ_CMD_S));

	// read address
	nfi_write32(snf, SNF_RD_CTL3, op_addr);

	// Set read op_mode
	if (op->data.buswidth == 4)
		rd_mode = op->addr.buswidth == 4 ? DATA_READ_MODE_QUAD :
						   DATA_READ_MODE_X4;
	else if (op->data.buswidth == 2)
		rd_mode = op->addr.buswidth == 2 ? DATA_READ_MODE_DUAL :
						   DATA_READ_MODE_X2;
	else
		rd_mode = DATA_READ_MODE_X1;
	rd_mode <<= DATA_READ_MODE_S;
	nfi_rmw32(snf, SNF_MISC_CTL, DATA_READ_MODE,
		  rd_mode | DATARD_CUSTOM_EN);

	// Set bytes to read
	rd_bytes = (snf->nfi_cfg.spare_size + snf->caps->sector_size) *
		   snf->nfi_cfg.nsectors;
	nfi_write32(snf, SNF_MISC_CTL2,
		    (rd_bytes << PROGRAM_LOAD_BYTE_NUM_S) | rd_bytes);

	// NFI read prepare
	nfi_write16(snf, NFI_CNFG,
		    (CNFG_OP_MODE_CUST << CNFG_OP_MODE_S) | CNFG_DMA_BURST_EN |
			    CNFG_READ_MODE | CNFG_DMA_MODE | op_mode);

	nfi_write32(snf, NFI_CON, (snf->nfi_cfg.nsectors << CON_SEC_NUM_S));

	buf_dma = dma_map_single(snf->dev, buf, dma_len, DMA_FROM_DEVICE);
	ret = dma_mapping_error(snf->dev, buf_dma);
	if (ret) {
		dev_err(snf->dev, "DMA mapping failed.\n");
		goto cleanup;
	}
	nfi_write32(snf, NFI_STRADDR, buf_dma);
	if (op->data.ecc) {
		snf->ecc_cfg->op = ECC_DECODE;
		ret = mtk_ecc_enable(snf->ecc, snf->ecc_cfg);
		if (ret)
			goto cleanup_dma;
	}
	// Prepare for custom read interrupt
	nfi_write32(snf, NFI_INTR_EN, NFI_IRQ_INTR_EN | NFI_IRQ_CUS_READ);
	reinit_completion(&snf->op_done);

	// Trigger NFI into custom mode
	nfi_write16(snf, NFI_CMD, NFI_CMD_DUMMY_READ);

	// Start DMA read
	nfi_rmw32(snf, NFI_CON, 0, CON_BRD);
	nfi_write16(snf, NFI_STRDATA, STR_DATA);

	if (!wait_for_completion_timeout(
		    &snf->op_done, usecs_to_jiffies(SNFI_POLL_INTERVAL))) {
		dev_err(snf->dev, "DMA timed out for reading from cache.\n");
		ret = -ETIMEDOUT;
		goto cleanup;
	}

	// Wait for BUS_SEC_CNTR returning expected value
	ret = readl_poll_timeout(snf->nfi_base + NFI_BYTELEN, val,
				 BUS_SEC_CNTR(val) >= snf->nfi_cfg.nsectors, 0,
				 SNFI_POLL_INTERVAL);
	if (ret) {
		dev_err(snf->dev, "Timed out waiting for BUS_SEC_CNTR\n");
		goto cleanup2;
	}

	// Wait for bus becoming idle
	ret = readl_poll_timeout(snf->nfi_base + NFI_MASTERSTA, val,
				 !(val & snf->caps->mastersta_mask), 0,
				 SNFI_POLL_INTERVAL);
	if (ret) {
		dev_err(snf->dev, "Timed out waiting for bus becoming idle\n");
		goto cleanup2;
	}

	if (op->data.ecc) {
		ret = mtk_ecc_wait_done(snf->ecc, ECC_DECODE);
		if (ret) {
			dev_err(snf->dev, "wait ecc done timeout\n");
			goto cleanup2;
		}
		// save status before disabling ecc
		mtk_ecc_get_stats(snf->ecc, &snf->ecc_stats,
				  snf->nfi_cfg.nsectors);
	}

	dma_unmap_single(snf->dev, buf_dma, dma_len, DMA_FROM_DEVICE);

	if (snf->autofmt) {
		mtk_snand_read_fdm(snf, buf_fdm);
		if (snf->caps->bbm_swap) {
			mtk_snand_bm_swap(snf, buf);
			mtk_snand_fdm_bm_swap(snf);
		}
	}

	// copy data back
	if (nfi_read32(snf, NFI_STA) & READ_EMPTY) {
		memset(op->data.buf.in, 0xff, op->data.nbytes);
		snf->ecc_stats.bitflips = 0;
		snf->ecc_stats.failed = 0;
		snf->ecc_stats.corrected = 0;
	} else {
		if (buf == op->data.buf.in) {
			u32 cap_len = snf->buf_len - snf->nfi_cfg.page_size;
			u32 req_left = op->data.nbytes - snf->nfi_cfg.page_size;

			if (req_left)
				memcpy(op->data.buf.in + snf->nfi_cfg.page_size,
				       buf_fdm,
				       cap_len < req_left ? cap_len : req_left);
		} else if (rd_offset < snf->buf_len) {
			u32 cap_len = snf->buf_len - rd_offset;

			if (op->data.nbytes < cap_len)
				cap_len = op->data.nbytes;
			memcpy(op->data.buf.in, snf->buf + rd_offset, cap_len);
		}
	}
cleanup2:
	if (op->data.ecc)
		mtk_ecc_disable(snf->ecc);
cleanup_dma:
	// unmap dma only if any error happens. (otherwise it's done before
	// data copying)
	if (ret)
		dma_unmap_single(snf->dev, buf_dma, dma_len, DMA_FROM_DEVICE);
cleanup:
	// Stop read
	nfi_write32(snf, NFI_CON, 0);
	nfi_write16(snf, NFI_CNFG, 0);

	// Clear SNF done flag
	nfi_rmw32(snf, SNF_STA_CTL1, 0, CUS_READ_DONE);
	nfi_write32(snf, SNF_STA_CTL1, 0);

	// Disable interrupt
	nfi_read32(snf, NFI_INTR_STA);
	nfi_write32(snf, NFI_INTR_EN, 0);

	nfi_rmw32(snf, SNF_MISC_CTL, DATARD_CUSTOM_EN, 0);
	return ret;
}

static int mtk_snand_write_page_cache(struct mtk_snand *snf,
				      const struct spi_mem_op *op)
{
	// the address part to be sent by the controller
	u32 op_addr = op->addr.val;
	// where to start copying data from bounce buffer
	u32 wr_offset = 0;
	u32 op_mode = 0;
	int ret = 0;
	u32 wr_mode = 0;
	u32 dma_len = snf->buf_len;
	u32 wr_bytes, val;
	size_t cap_len;
	dma_addr_t buf_dma;

	if (snf->autofmt) {
		u32 last_bit;
		u32 mask;

		dma_len = snf->nfi_cfg.page_size;
		op_mode = CNFG_AUTO_FMT_EN;
		if (op->data.ecc)
			op_mode |= CNFG_HW_ECC_EN;

		last_bit = fls(snf->nfi_cfg.page_size + snf->nfi_cfg.oob_size);
		mask = (1 << last_bit) - 1;
		wr_offset = op_addr & mask;
		op_addr &= ~mask;
	}
	mtk_snand_mac_reset(snf);
	mtk_nfi_reset(snf);

	if (wr_offset)
		memset(snf->buf, 0xff, wr_offset);

	cap_len = snf->buf_len - wr_offset;
	if (op->data.nbytes < cap_len)
		cap_len = op->data.nbytes;
	memcpy(snf->buf + wr_offset, op->data.buf.out, cap_len);
	if (snf->autofmt) {
		if (snf->caps->bbm_swap) {
			mtk_snand_fdm_bm_swap(snf);
			mtk_snand_bm_swap(snf, snf->buf);
		}
		mtk_snand_write_fdm(snf, snf->buf + snf->nfi_cfg.page_size);
	}

	// Command
	nfi_write32(snf, SNF_PG_CTL1, (op->cmd.opcode << PG_LOAD_CMD_S));

	// write address
	nfi_write32(snf, SNF_PG_CTL2, op_addr);

	// Set read op_mode
	if (op->data.buswidth == 4)
		wr_mode = PG_LOAD_X4_EN;

	nfi_rmw32(snf, SNF_MISC_CTL, PG_LOAD_X4_EN,
		  wr_mode | PG_LOAD_CUSTOM_EN);

	// Set bytes to write
	wr_bytes = (snf->nfi_cfg.spare_size + snf->caps->sector_size) *
		   snf->nfi_cfg.nsectors;
	nfi_write32(snf, SNF_MISC_CTL2,
		    (wr_bytes << PROGRAM_LOAD_BYTE_NUM_S) | wr_bytes);

	// NFI write prepare
	nfi_write16(snf, NFI_CNFG,
		    (CNFG_OP_MODE_PROGRAM << CNFG_OP_MODE_S) |
			    CNFG_DMA_BURST_EN | CNFG_DMA_MODE | op_mode);

	nfi_write32(snf, NFI_CON, (snf->nfi_cfg.nsectors << CON_SEC_NUM_S));
	buf_dma = dma_map_single(snf->dev, snf->buf, dma_len, DMA_TO_DEVICE);
	ret = dma_mapping_error(snf->dev, buf_dma);
	if (ret) {
		dev_err(snf->dev, "DMA mapping failed.\n");
		goto cleanup;
	}
	nfi_write32(snf, NFI_STRADDR, buf_dma);
	if (op->data.ecc) {
		snf->ecc_cfg->op = ECC_ENCODE;
		ret = mtk_ecc_enable(snf->ecc, snf->ecc_cfg);
		if (ret)
			goto cleanup_dma;
	}
	// Prepare for custom write interrupt
	nfi_write32(snf, NFI_INTR_EN, NFI_IRQ_INTR_EN | NFI_IRQ_CUS_PG);
	reinit_completion(&snf->op_done);
	;

	// Trigger NFI into custom mode
	nfi_write16(snf, NFI_CMD, NFI_CMD_DUMMY_WRITE);

	// Start DMA write
	nfi_rmw32(snf, NFI_CON, 0, CON_BWR);
	nfi_write16(snf, NFI_STRDATA, STR_DATA);

	if (!wait_for_completion_timeout(
		    &snf->op_done, usecs_to_jiffies(SNFI_POLL_INTERVAL))) {
		dev_err(snf->dev, "DMA timed out for program load.\n");
		ret = -ETIMEDOUT;
		goto cleanup_ecc;
	}

	// Wait for NFI_SEC_CNTR returning expected value
	ret = readl_poll_timeout(snf->nfi_base + NFI_ADDRCNTR, val,
				 NFI_SEC_CNTR(val) >= snf->nfi_cfg.nsectors, 0,
				 SNFI_POLL_INTERVAL);
	if (ret)
		dev_err(snf->dev, "Timed out waiting for NFI_SEC_CNTR\n");

cleanup_ecc:
	if (op->data.ecc)
		mtk_ecc_disable(snf->ecc);
cleanup_dma:
	dma_unmap_single(snf->dev, buf_dma, dma_len, DMA_TO_DEVICE);
cleanup:
	// Stop write
	nfi_write32(snf, NFI_CON, 0);
	nfi_write16(snf, NFI_CNFG, 0);

	// Clear SNF done flag
	nfi_rmw32(snf, SNF_STA_CTL1, 0, CUS_PG_DONE);
	nfi_write32(snf, SNF_STA_CTL1, 0);

	// Disable interrupt
	nfi_read32(snf, NFI_INTR_STA);
	nfi_write32(snf, NFI_INTR_EN, 0);

	nfi_rmw32(snf, SNF_MISC_CTL, PG_LOAD_CUSTOM_EN, 0);

	return ret;
}

/**
 * mtk_snand_is_page_ops() - check if the op is a controller supported page op.
 * @op spi-mem op to check
 *
 * Check whether op can be executed with read_from_cache or program_load
 * mode in the controller.
 * This controller can execute typical Read From Cache and Program Load
 * instructions found on SPI-NAND with 2-byte address.
 * DTR and cmd buswidth & nbytes should be checked before calling this.
 *
 * Return: true if the op matches the instruction template
 */
static bool mtk_snand_is_page_ops(const struct spi_mem_op *op)
{
	if (op->addr.nbytes != 2)
		return false;

	if (op->addr.buswidth != 1 && op->addr.buswidth != 2 &&
	    op->addr.buswidth != 4)
		return false;

	// match read from page instructions
	if (op->data.dir == SPI_MEM_DATA_IN) {
		// check dummy cycle first
		if (op->dummy.nbytes * BITS_PER_BYTE / op->dummy.buswidth >
		    DATA_READ_MAX_DUMMY)
			return false;
		// quad io / quad out
		if ((op->addr.buswidth == 4 || op->addr.buswidth == 1) &&
		    op->data.buswidth == 4)
			return true;

		// dual io / dual out
		if ((op->addr.buswidth == 2 || op->addr.buswidth == 1) &&
		    op->data.buswidth == 2)
			return true;

		// standard spi
		if (op->addr.buswidth == 1 && op->data.buswidth == 1)
			return true;
	} else if (op->data.dir == SPI_MEM_DATA_OUT) {
		// check dummy cycle first
		if (op->dummy.nbytes)
			return false;
		// program load quad out
		if (op->addr.buswidth == 1 && op->data.buswidth == 4)
			return true;
		// standard spi
		if (op->addr.buswidth == 1 && op->data.buswidth == 1)
			return true;
	}
	return false;
}

static bool mtk_snand_supports_op(struct spi_mem *mem,
				  const struct spi_mem_op *op)
{
	if (!spi_mem_default_supports_op(mem, op))
		return false;
	if (op->cmd.nbytes != 1 || op->cmd.buswidth != 1)
		return false;
	if (mtk_snand_is_page_ops(op))
		return true;
	return ((op->addr.nbytes == 0 || op->addr.buswidth == 1) &&
		(op->dummy.nbytes == 0 || op->dummy.buswidth == 1) &&
		(op->data.nbytes == 0 || op->data.buswidth == 1));
}

static int mtk_snand_adjust_op_size(struct spi_mem *mem, struct spi_mem_op *op)
{
	struct mtk_snand *ms = spi_controller_get_devdata(mem->spi->master);
	// page ops transfer size must be exactly ((sector_size + spare_size) *
	// nsectors). Limit the op size if the caller requests more than that.
	// exec_op will read more than needed and discard the leftover if the
	// caller requests less data.
	if (mtk_snand_is_page_ops(op)) {
		size_t l;
		// skip adjust_op_size for page ops
		if (ms->autofmt)
			return 0;
		l = ms->caps->sector_size + ms->nfi_cfg.spare_size;
		l *= ms->nfi_cfg.nsectors;
		if (op->data.nbytes > l)
			op->data.nbytes = l;
	} else {
		size_t hl = op->cmd.nbytes + op->addr.nbytes + op->dummy.nbytes;

		if (hl >= SNF_GPRAM_SIZE)
			return -EOPNOTSUPP;
		if (op->data.nbytes > SNF_GPRAM_SIZE - hl)
			op->data.nbytes = SNF_GPRAM_SIZE - hl;
	}
	return 0;
}

static int mtk_snand_exec_op(struct spi_mem *mem, const struct spi_mem_op *op)
{
	struct mtk_snand *ms = spi_controller_get_devdata(mem->spi->master);

	dev_dbg(ms->dev, "OP %02x ADDR %08llX@%d:%u DATA %d:%u", op->cmd.opcode,
		op->addr.val, op->addr.buswidth, op->addr.nbytes,
		op->data.buswidth, op->data.nbytes);
	if (mtk_snand_is_page_ops(op)) {
		if (op->data.dir == SPI_MEM_DATA_IN)
			return mtk_snand_read_page_cache(ms, op);
		else
			return mtk_snand_write_page_cache(ms, op);
	} else {
		return mtk_snand_mac_io(ms, op);
	}
}

static const struct spi_controller_mem_ops mtk_snand_mem_ops = {
	.adjust_op_size = mtk_snand_adjust_op_size,
	.supports_op = mtk_snand_supports_op,
	.exec_op = mtk_snand_exec_op,
};

static const struct spi_controller_mem_caps mtk_snand_mem_caps = {
	.ecc = true,
};

static irqreturn_t mtk_snand_irq(int irq, void *id)
{
	struct mtk_snand *snf = id;
	u32 sta, ien;

	sta = nfi_read32(snf, NFI_INTR_STA);
	ien = nfi_read32(snf, NFI_INTR_EN);

	if (!(sta & ien))
		return IRQ_NONE;

	nfi_write32(snf, NFI_INTR_EN, 0);
	complete(&snf->op_done);
	return IRQ_HANDLED;
}

static const struct of_device_id mtk_snand_ids[] = {
	{ .compatible = "mediatek,mt7622-snand", .data = &mt7622_snand_caps },
	{ .compatible = "mediatek,mt7629-snand", .data = &mt7629_snand_caps },
	{},
};

MODULE_DEVICE_TABLE(of, mtk_snand_ids);

static int mtk_snand_enable_clk(struct mtk_snand *ms)
{
	int ret;

	ret = clk_prepare_enable(ms->nfi_clk);
	if (ret) {
		dev_err(ms->dev, "unable to enable nfi clk\n");
		return ret;
	}
	ret = clk_prepare_enable(ms->pad_clk);
	if (ret) {
		dev_err(ms->dev, "unable to enable pad clk\n");
		goto err1;
	}
	return 0;
err1:
	clk_disable_unprepare(ms->nfi_clk);
	return ret;
}

static void mtk_snand_disable_clk(struct mtk_snand *ms)
{
	clk_disable_unprepare(ms->pad_clk);
	clk_disable_unprepare(ms->nfi_clk);
}

static int mtk_snand_probe(struct platform_device *pdev)
{
	struct device_node *np = pdev->dev.of_node;
	const struct of_device_id *dev_id;
	struct spi_controller *ctlr;
	struct mtk_snand *ms;
	int ret;

	dev_id = of_match_node(mtk_snand_ids, np);
	if (!dev_id)
		return -EINVAL;

	ctlr = devm_spi_alloc_master(&pdev->dev, sizeof(*ms));
	if (!ctlr)
		return -ENOMEM;
	platform_set_drvdata(pdev, ctlr);

	ms = spi_controller_get_devdata(ctlr);

	ms->ctlr = ctlr;
	ms->caps = dev_id->data;

	ms->ecc = of_mtk_ecc_get(np);
	if (IS_ERR(ms->ecc))
		return PTR_ERR(ms->ecc);
	else if (!ms->ecc)
		return -ENODEV;

	ms->nfi_base = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(ms->nfi_base)) {
		ret = PTR_ERR(ms->nfi_base);
		goto release_ecc;
	}

	ms->dev = &pdev->dev;

	ms->nfi_clk = devm_clk_get(&pdev->dev, "nfi_clk");
	if (IS_ERR(ms->nfi_clk)) {
		ret = PTR_ERR(ms->nfi_clk);
		dev_err(&pdev->dev, "unable to get nfi_clk, err = %d\n", ret);
		goto release_ecc;
	}

	ms->pad_clk = devm_clk_get(&pdev->dev, "pad_clk");
	if (IS_ERR(ms->pad_clk)) {
		ret = PTR_ERR(ms->pad_clk);
		dev_err(&pdev->dev, "unable to get pad_clk, err = %d\n", ret);
		goto release_ecc;
	}

	ret = mtk_snand_enable_clk(ms);
	if (ret)
		goto release_ecc;

	init_completion(&ms->op_done);

	ms->irq = platform_get_irq(pdev, 0);
	if (ms->irq < 0) {
		ret = ms->irq;
		goto disable_clk;
	}
	ret = devm_request_irq(ms->dev, ms->irq, mtk_snand_irq, 0x0,
			       "mtk-snand", ms);
	if (ret) {
		dev_err(ms->dev, "failed to request snfi irq\n");
		goto disable_clk;
	}

	ret = dma_set_mask(ms->dev, DMA_BIT_MASK(32));
	if (ret) {
		dev_err(ms->dev, "failed to set dma mask\n");
		goto disable_clk;
	}

	// switch to SNFI mode
	nfi_write32(ms, SNF_CFG, SPI_MODE);

	// setup an initial page format for ops matching page_cache_op template
	// before ECC is called.
	ret = mtk_snand_setup_pagefmt(ms, ms->caps->sector_size,
				      ms->caps->spare_sizes[0]);
	if (ret) {
		dev_err(ms->dev, "failed to set initial page format\n");
		goto disable_clk;
	}

	// setup ECC engine
	ms->ecc_eng.dev = &pdev->dev;
	ms->ecc_eng.integration = NAND_ECC_ENGINE_INTEGRATION_PIPELINED;
	ms->ecc_eng.ops = &mtk_snfi_ecc_engine_ops;
	ms->ecc_eng.priv = ms;

	ret = nand_ecc_register_on_host_hw_engine(&ms->ecc_eng);
	if (ret) {
		dev_err(&pdev->dev, "failed to register ecc engine.\n");
		goto disable_clk;
	}

	ctlr->num_chipselect = 1;
	ctlr->mem_ops = &mtk_snand_mem_ops;
	ctlr->mem_caps = &mtk_snand_mem_caps;
	ctlr->bits_per_word_mask = SPI_BPW_MASK(8);
	ctlr->mode_bits = SPI_RX_DUAL | SPI_RX_QUAD | SPI_TX_DUAL | SPI_TX_QUAD;
	ctlr->dev.of_node = pdev->dev.of_node;
	ret = spi_register_controller(ctlr);
	if (ret) {
		dev_err(&pdev->dev, "spi_register_controller failed.\n");
		goto disable_clk;
	}

	return 0;
disable_clk:
	mtk_snand_disable_clk(ms);
release_ecc:
	mtk_ecc_release(ms->ecc);
	return ret;
}

static int mtk_snand_remove(struct platform_device *pdev)
{
	struct spi_controller *ctlr = platform_get_drvdata(pdev);
	struct mtk_snand *ms = spi_controller_get_devdata(ctlr);

	spi_unregister_controller(ctlr);
	mtk_snand_disable_clk(ms);
	mtk_ecc_release(ms->ecc);
	kfree(ms->buf);
	return 0;
}

static struct platform_driver mtk_snand_driver = {
	.probe = mtk_snand_probe,
	.remove = mtk_snand_remove,
	.driver = {
		.name = "mtk-snand",
		.of_match_table = mtk_snand_ids,
	},
};

module_platform_driver(mtk_snand_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Chuanhong Guo <gch981213@gmail.com>");
MODULE_DESCRIPTION("MeidaTek SPI-NAND Flash Controller Driver");