Re: [PATCH V5 RESEND] mtd: rawnand: Add Loongson1 NAND driver

[Miquel Raynal <miquel.raynal@bootlin.com>]

Hi Keguang,

Sorry again for the very late review, here are my comments.

Keguang Zhang <keguang.zhang@gmail.com> wrote on Fri, 21 May 2021
06:42:13 +0800:

> From: Kelvin Cheung <keguang.zhang@gmail.com>
> 
> This patch adds NAND driver for Loongson1B.
> 
> Signed-off-by: Kelvin Cheung <keguang.zhang@gmail.com>
> ---
> V4 -> V5:
>    Update the driver to fit the raw NAND framework.
>    Implement exec_op() instead of legacy cmdfunc().
>    Use dma_request_chan() instead of dma_request_channel().
>    Some minor fixes and cleanups.
> V3 -> V4:
>    Retrieve the controller from nand_hw_control.
> V2 -> V3:
>    Replace __raw_readl/__raw_writel with readl/writel.
>    Split ls1x_nand into two structures: ls1x_nand_chip and
>    ls1x_nand_controller.
> V1 -> V2:
>    Modify the dependency in Kconfig due to the changes of DMA
>    module.
> ---
>  drivers/mtd/nand/raw/Kconfig          |   8 +
>  drivers/mtd/nand/raw/Makefile         |   1 +
>  drivers/mtd/nand/raw/loongson1_nand.c | 770 ++++++++++++++++++++++++++
>  3 files changed, 779 insertions(+)
>  create mode 100644 drivers/mtd/nand/raw/loongson1_nand.c
> 
> diff --git a/drivers/mtd/nand/raw/Kconfig b/drivers/mtd/nand/raw/Kconfig
> index 30f061939560..63402e335df4 100644
> --- a/drivers/mtd/nand/raw/Kconfig
> +++ b/drivers/mtd/nand/raw/Kconfig
> @@ -453,6 +453,14 @@ config MTD_NAND_ROCKCHIP
>  	    NFC v800: RK3308, RV1108
>  	    NFC v900: PX30, RK3326
>  
> +config MTD_NAND_LOONGSON1
> +	tristate "Support for Loongson1 SoC NAND controller"

Can you please match the style for the titles?

> +	depends on MACH_LOONGSON32

 || CROSS_COMPILE

> +	select MTD_NAND_ECC_SW_HAMMING
> +	select LOONGSON1_DMA

Maybe this should be a depends on?

> +	help
> +	  Enables support for NAND controller on Loongson1 SoCs.
> +
>  comment "Misc"
>  
>  config MTD_SM_COMMON
> diff --git a/drivers/mtd/nand/raw/Makefile b/drivers/mtd/nand/raw/Makefile
> index d011c6c53f8f..50a51ad6ec21 100644
> --- a/drivers/mtd/nand/raw/Makefile
> +++ b/drivers/mtd/nand/raw/Makefile
> @@ -57,6 +57,7 @@ obj-$(CONFIG_MTD_NAND_CADENCE)		+= cadence-nand-controller.o
>  obj-$(CONFIG_MTD_NAND_ARASAN)		+= arasan-nand-controller.o
>  obj-$(CONFIG_MTD_NAND_INTEL_LGM)	+= intel-nand-controller.o
>  obj-$(CONFIG_MTD_NAND_ROCKCHIP)		+= rockchip-nand-controller.o
> +obj-$(CONFIG_MTD_NAND_LOONGSON1)        += loongson1_nand.o
>  
>  nand-objs := nand_base.o nand_legacy.o nand_bbt.o nand_timings.o nand_ids.o
>  nand-objs += nand_onfi.o
> diff --git a/drivers/mtd/nand/raw/loongson1_nand.c b/drivers/mtd/nand/raw/loongson1_nand.c
> new file mode 100644
> index 000000000000..b06e36ec32da
> --- /dev/null
> +++ b/drivers/mtd/nand/raw/loongson1_nand.c
> @@ -0,0 +1,770 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * NAND Flash Driver for Loongson 1 SoC
> + *
> + * Copyright (C) 2015-2021 Zhang, Keguang <keguang.zhang@gmail.com>
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/clk.h>
> +#include <linux/dmaengine.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/iopoll.h>
> +#include <linux/mtd/mtd.h>
> +#include <linux/mtd/rawnand.h>
> +#include <linux/platform_device.h>
> +#include <linux/sizes.h>
> +
> +#include <nand.h>
> +
> +/* Loongson 1 NAND Register Definitions */
> +#define NAND_CMD		0x0
> +#define NAND_ADDR1		0x4
> +#define NAND_ADDR2		0x8
> +#define NAND_TIMING		0xc
> +#define NAND_IDL		0x10
> +#define NAND_IDH		0x14
> +#define NAND_STATUS		0x15
> +#define NAND_PARAM		0x18
> +#define NAND_OP_NUM		0x1c
> +#define NAND_CS_RDY		0x20
> +
> +#define NAND_DMA_ADDR		0x40
> +
> +/* NAND Command Register Bits */
> +#define OP_DONE			BIT(10)
> +#define OP_SPARE		BIT(9)
> +#define OP_MAIN			BIT(8)
> +#define CMD_STATUS		BIT(7)
> +#define CMD_RESET		BIT(6)
> +#define CMD_READID		BIT(5)
> +#define BLOCKS_ERASE		BIT(4)
> +#define CMD_ERASE		BIT(3)
> +#define CMD_WRITE		BIT(2)
> +#define CMD_READ		BIT(1)
> +#define CMD_VALID		BIT(0)
> +
> +#define MAX_ADDR_CYC		5U
> +#define MAX_ID_SIZE		(NAND_STATUS - NAND_IDL)

Strange. I guess you can hardcode it.

> +#define SIZE_MASK		GENMASK(11, 8)
> +
> +#define BITS_PER_WORD		32
> +
> +/* macros for registers read/write */
> +#define nand_readl(nc, off)		\
> +	readl((nc)->reg_base + (off))
> +
> +#define nand_writel(nc, off, val)	\
> +	writel((val), (nc)->reg_base + (off))
> +
> +struct ls1x_nand_controller {
> +	void __iomem *reg_base;
> +	__le32 addr1_reg;
> +	__le32 addr2_reg;
> +
> +	char *buf;
> +	unsigned int len;
> +	unsigned int rdy_timeout;
> +
> +	/* DMA Engine stuff */
> +	struct dma_chan *dma_chan;
> +	dma_cookie_t dma_cookie;
> +	struct completion dma_complete;
> +};
> +
> +struct ls1x_nand {
> +	struct device *dev;
> +	struct clk *clk;
> +	struct nand_chip chip;
> +	struct nand_controller controller;
> +	struct ls1x_nand_controller nc;
> +	struct plat_ls1x_nand *pdata;
> +};
> +
> +static void ls1x_nand_dump_regs(struct nand_chip *chip)
> +{
> +	struct ls1x_nand *nand = nand_get_controller_data(chip);
> +	struct ls1x_nand_controller *nc = &nand->nc;
> +
> +	print_hex_dump(KERN_INFO, "REG: ", DUMP_PREFIX_OFFSET, 16, 4,
> +		       nc->reg_base, 0x44, false);
> +}
> +
> +static void ls1x_nand_dma_callback(void *data)
> +{
> +	struct ls1x_nand *nand = (struct ls1x_nand *)data;
> +	struct ls1x_nand_controller *nc = &nand->nc;
> +	enum dma_status status;
> +
> +	status = dmaengine_tx_status(nc->dma_chan, nc->dma_cookie, NULL);
> +	if (likely(status == DMA_COMPLETE))
> +		dev_dbg(nand->dev, "DMA complete with cookie=%d\n",
> +			nc->dma_cookie);
> +	else
> +		dev_err(nand->dev, "DMA error with cookie=%d\n",
> +			nc->dma_cookie);
> +
> +	complete(&nc->dma_complete);
> +}
> +
> +static int ls1x_nand_dma_transfer(struct ls1x_nand *nand, bool is_write)
> +{
> +	struct ls1x_nand_controller *nc = &nand->nc;
> +	struct dma_chan *chan = nc->dma_chan;
> +	struct dma_async_tx_descriptor *desc;
> +	enum dma_data_direction data_dir =
> +	    is_write ? DMA_TO_DEVICE : DMA_FROM_DEVICE;
> +	enum dma_transfer_direction xfer_dir =
> +	    is_write ? DMA_MEM_TO_DEV : DMA_DEV_TO_MEM;
> +	dma_addr_t dma_addr;
> +	int ret;
> +
> +	dma_addr = dma_map_single(chan->device->dev, nc->buf, nc->len,
> +				  data_dir);
> +	if (dma_mapping_error(chan->device->dev, dma_addr)) {
> +		dev_err(nand->dev, "failed to map DMA buffer!\n");
> +		return -ENXIO;
> +	}
> +
> +	desc = dmaengine_prep_slave_single(chan, dma_addr, nc->len, xfer_dir,
> +					   DMA_PREP_INTERRUPT);
> +	if (!desc) {
> +		dev_err(nand->dev, "failed to prepare DMA descriptor!\n");
> +		ret = PTR_ERR(desc);
> +		goto err;
> +	}
> +	desc->callback = ls1x_nand_dma_callback;
> +	desc->callback_param = nand;
> +
> +	nc->dma_cookie = dmaengine_submit(desc);
> +	ret = dma_submit_error(nc->dma_cookie);
> +	if (ret) {
> +		dev_err(nand->dev, "failed to submit DMA descriptor!\n");
> +		goto err;
> +	}
> +
> +	dev_dbg(nand->dev, "issue DMA with cookie=%d\n", nc->dma_cookie);
> +	dma_async_issue_pending(chan);
> +
> +	ret = wait_for_completion_timeout(&nc->dma_complete,
> +					  msecs_to_jiffies(nc->rdy_timeout));
> +	if (ret <= 0) {
> +		dev_err(nand->dev, "DMA timeout!\n");
> +		dmaengine_terminate_all(chan);
> +		ret = -EIO;
> +	}
> +	ret = 0;
> +err:
> +	dma_unmap_single(chan->device->dev, dma_addr, nc->len, data_dir);
> +
> +	return ret;
> +}
> +
> +static inline void ls1x_nand_parse_address(struct nand_chip *chip,
> +					   const u8 *addrs,
> +					   unsigned int naddrs, int cmd)
> +{
> +	struct ls1x_nand *nand = nand_get_controller_data(chip);
> +	struct ls1x_nand_controller *nc = &nand->nc;
> +#if defined(CONFIG_LOONGSON1_LS1B)

Please use a regular if (IS_DEFINED())

I don't like this symbol anyway, you should get this information from a
compatible (like the machine compatible) not from a Kconfig symbol.

> +	unsigned int page_shift = chip->page_shift + 1;
> +#endif
> +	int i;
> +
> +	nc->addr1_reg = 0;
> +	nc->addr2_reg = 0;
> +#if defined(CONFIG_LOONGSON1_LS1B)
> +	if (cmd == CMD_ERASE) {
> +		page_shift = chip->page_shift;
> +
> +		for (i = 0; i < min(MAX_ADDR_CYC - 2, naddrs); i++)
> +			nc->addr1_reg |=
> +			    (u32)addrs[i] << (page_shift + BITS_PER_BYTE * i);
> +		if (i == MAX_ADDR_CYC - 2)
> +			nc->addr2_reg |=
> +			    (u32)addrs[i] >> (BITS_PER_WORD - page_shift -
> +					      BITS_PER_BYTE * (i - 1));
> +
> +		return;
> +	}
> +
> +	for (i = 0; i < min(2U, naddrs); i++)
> +		nc->addr1_reg |= (u32)addrs[i] << BITS_PER_BYTE * i;
> +	for (i = 2; i < min(MAX_ADDR_CYC, naddrs); i++)
> +		nc->addr1_reg |=
> +		    (u32)addrs[i] << (page_shift + BITS_PER_BYTE * (i - 2));
> +	if (i == MAX_ADDR_CYC)
> +		nc->addr2_reg |=
> +		    (u32)addrs[i] >> (BITS_PER_WORD - page_shift -
> +				      BITS_PER_BYTE * (i - 1));
> +#elif defined(CONFIG_LOONGSON1_LS1C)
> +	if (cmd == CMD_ERASE) {
> +		for (i = 0; i < min(MAX_ADDR_CYC, naddrs); i++)
> +			nc->addr2_reg |= (u32)addrs[i] << BITS_PER_BYTE * i;
> +
> +		return;
> +	}
> +
> +	for (i = 0; i < min(MAX_ADDR_CYC, naddrs); i++) {
> +		if (i < 2)
> +			nc->addr1_reg |= (u32)addrs[i] << BITS_PER_BYTE * i;
> +		else
> +			nc->addr2_reg |=
> +			    (u32)addrs[i] << BITS_PER_BYTE * (i - 2);
> +	}
> +#endif
> +}
> +
> +static int ls1x_nand_set_controller(struct nand_chip *chip,
> +				    const struct nand_subop *subop, int cmd)
> +{
> +	struct ls1x_nand *nand = nand_get_controller_data(chip);
> +	struct ls1x_nand_controller *nc = &nand->nc;
> +	unsigned int op_id;
> +
> +	nc->buf = NULL;
> +	nc->len = 0;
> +	nc->rdy_timeout = 0;
> +
> +	for (op_id = 0; op_id < subop->ninstrs; op_id++) {
> +		const struct nand_op_instr *instr = &subop->instrs[op_id];
> +		unsigned int offset, naddrs;
> +		const u8 *addrs;
> +
> +		switch (instr->type) {
> +		case NAND_OP_CMD_INSTR:
> +			break;

This is very suspicious. You should definitely do something with the
command bytes, you should not guess the commands based on the format of
the operation.

> +		case NAND_OP_ADDR_INSTR:
> +			offset = nand_subop_get_addr_start_off(subop, op_id);
> +			naddrs = nand_subop_get_num_addr_cyc(subop, op_id);
> +			addrs = &instr->ctx.addr.addrs[offset];
> +
> +			ls1x_nand_parse_address(chip, addrs, naddrs, cmd);
> +			/* set NAND address */
> +			nand_writel(nc, NAND_ADDR1, nc->addr1_reg);
> +			nand_writel(nc, NAND_ADDR2, nc->addr2_reg);
> +			break;
> +		case NAND_OP_DATA_IN_INSTR:
> +			offset = nand_subop_get_data_start_off(subop, op_id);
> +			nc->len = nand_subop_get_data_len(subop, op_id);
> +			nc->buf = instr->ctx.data.buf.in + offset;
> +
> +			if (!IS_ALIGNED(nc->len, chip->buf_align) ||
> +			    !IS_ALIGNED((unsigned int)nc->buf, chip->buf_align))
> +				return -ENOTSUPP;
> +			/* set NAND data length */
> +			nand_writel(nc, NAND_OP_NUM, nc->len);
> +			break;
> +		case NAND_OP_DATA_OUT_INSTR:
> +			offset = nand_subop_get_data_start_off(subop, op_id);
> +			nc->len = nand_subop_get_data_len(subop, op_id);
> +			nc->buf = (void *)instr->ctx.data.buf.out + offset;
> +
> +			if (!IS_ALIGNED(nc->len, chip->buf_align) ||
> +			    !IS_ALIGNED((unsigned int)nc->buf, chip->buf_align))
> +				return -ENOTSUPP;
> +			/* set NAND data length */
> +			nand_writel(nc, NAND_OP_NUM, nc->len);
> +			break;
> +		case NAND_OP_WAITRDY_INSTR:
> +			nc->rdy_timeout = instr->ctx.waitrdy.timeout_ms;
> +			break;
> +		}
> +	}
> +
> +	/*set NAND erase block count */
> +	if (cmd & CMD_ERASE)
> +		nand_writel(nc, NAND_OP_NUM, 1);
> +	/*set NAND operation region */

Please fix all your comments in the driver, eg:

	/* Set NAND operation region */

> +	if (nc->buf && nc->len) {
> +		if (nc->addr1_reg & BIT(chip->page_shift))
> +			cmd |= OP_SPARE;
> +		else
> +			cmd |= OP_SPARE | OP_MAIN;

Is this really needed? Can't you always stick to OP_SPARE | OP_MAIN?

> +	}
> +
> +	/*set NAND command */
> +	nand_writel(nc, NAND_CMD, cmd);
> +	/* Trigger operation */
> +	nand_writel(nc, NAND_CMD, nand_readl(nc, NAND_CMD) | CMD_VALID);
> +
> +	return 0;
> +}
> +
> +static inline int ls1x_nand_wait_for_op_done(struct ls1x_nand_controller *nc)
> +{
> +	unsigned int val;
> +	int ret = 0;
> +
> +	/* Wait for operation done */
> +	if (nc->rdy_timeout)
> +		ret = readl_relaxed_poll_timeout(nc->reg_base + NAND_CMD, val,
> +						 val & OP_DONE, 0,
> +						 nc->rdy_timeout * 1000);
> +
> +	return ret;
> +}
> +
> +static int ls1x_nand_reset_exec(struct nand_chip *chip,
> +				const struct nand_subop *subop)
> +{
> +	struct ls1x_nand *nand = nand_get_controller_data(chip);
> +	struct ls1x_nand_controller *nc = &nand->nc;
> +	int ret;
> +
> +	ls1x_nand_set_controller(chip, subop, CMD_RESET);
> +
> +	ret = ls1x_nand_wait_for_op_done(nc);
> +	if (ret)
> +		dev_err(nand->dev, "CMD_RESET failed! %d\n", ret);
> +
> +	return ret;
> +}
> +
> +static int ls1x_nand_read_id_exec(struct nand_chip *chip,
> +				  const struct nand_subop *subop)
> +{
> +	struct ls1x_nand *nand = nand_get_controller_data(chip);
> +	struct ls1x_nand_controller *nc = &nand->nc;
> +	int idl, i;
> +	int ret;
> +
> +	ls1x_nand_set_controller(chip, subop, CMD_READID);
> +
> +	ret = ls1x_nand_wait_for_op_done(nc);
> +	if (ret) {
> +		dev_err(nand->dev, "CMD_READID failed! %d\n", ret);
> +		return ret;
> +	}
> +
> +	idl = (nand_readl(nc, NAND_IDL));

Unneeded outer ( ).

> +	for (i = 0; i < min_t(unsigned int, nc->len, MAX_ID_SIZE); i++)

The core enforces the number of data cycles to be less or
equal than MAX_ID_SIZE if correctly described below (see the comment in
the exec_op array) so you don't need this min_t() here.

Please use { } to enclose the if/else block.

> +		if (i > 0)

This looks very suspicious, I would expect the condition to be i < 4

> +			nc->buf[i] = *((char *)&idl + 4 - i);

Please rewrite this, it is hard to follow.

> +		else
> +			nc->buf[i] = (char)(nand_readl(nc, NAND_IDH));
> +
> +	return ret;
> +}
> +
> +static int ls1x_nand_erase_exec(struct nand_chip *chip,
> +				const struct nand_subop *subop)
> +{
> +	struct ls1x_nand *nand = nand_get_controller_data(chip);
> +	struct ls1x_nand_controller *nc = &nand->nc;
> +	int ret;
> +
> +	ls1x_nand_set_controller(chip, subop, CMD_ERASE);
> +
> +	ret = ls1x_nand_wait_for_op_done(nc);
> +	if (ret)
> +		dev_err(nand->dev, "CMD_ERASE failed! %d\n", ret);
> +
> +	return ret;
> +}
> +
> +static int ls1x_nand_read_exec(struct nand_chip *chip,
> +			       const struct nand_subop *subop)
> +{
> +	struct ls1x_nand *nand = nand_get_controller_data(chip);
> +	struct ls1x_nand_controller *nc = &nand->nc;
> +	int ret;
> +
> +	ls1x_nand_set_controller(chip, subop, CMD_READ);
> +
> +	ret = ls1x_nand_dma_transfer(nand, false);

Please use an intermediate variable such as bool write = false; (same
below)

> +	if (ret)
> +		return ret;
> +
> +	ret = ls1x_nand_wait_for_op_done(nc);
> +	if (ret)
> +		dev_err(nand->dev, "CMD_READ failed! %d\n", ret);
> +
> +	return ret;
> +}
> +
> +static int ls1x_nand_write_exec(struct nand_chip *chip,
> +				const struct nand_subop *subop)
> +{
> +	struct ls1x_nand *nand = nand_get_controller_data(chip);
> +	struct ls1x_nand_controller *nc = &nand->nc;
> +	int ret;
> +
> +	ls1x_nand_set_controller(chip, subop, CMD_WRITE);
> +
> +	ret = ls1x_nand_dma_transfer(nand, true);
> +	if (ret)
> +		return ret;
> +
> +	ret = ls1x_nand_wait_for_op_done(nc);
> +	if (ret)
> +		dev_err(nand->dev, "CMD_WRITE failed! %d\n", ret);
> +
> +	return ret;
> +}
> +
> +static int ls1x_nand_read_status_exec(struct nand_chip *chip,
> +				      const struct nand_subop *subop)
> +{
> +	struct ls1x_nand *nand = nand_get_controller_data(chip);
> +	struct ls1x_nand_controller *nc = &nand->nc;
> +	int ret;
> +
> +	ls1x_nand_set_controller(chip, subop, CMD_STATUS);
> +
> +	ret = ls1x_nand_wait_for_op_done(nc);
> +	if (ret) {
> +		dev_err(nand->dev, "CMD_STATUS failed! %d\n", ret);
> +		return ret;
> +	}
> +
> +	nc->buf[0] = nand_readl(nc, NAND_IDH) >> BITS_PER_BYTE;

This looks very specific to the status cmd, which is not a valid
implementation. Can you turn this function generic to any cmd+data
bytes? (the number of data bytes could be different than 1).

> +
> +	return ret;
> +}
> +
> +static const struct nand_op_parser ls1x_nand_op_parser = NAND_OP_PARSER(
> +	NAND_OP_PARSER_PATTERN(
> +		ls1x_nand_reset_exec,
> +		NAND_OP_PARSER_PAT_CMD_ELEM(false),
> +		NAND_OP_PARSER_PAT_WAITRDY_ELEM(false)),
> +	NAND_OP_PARSER_PATTERN(
> +		ls1x_nand_read_id_exec,
> +		NAND_OP_PARSER_PAT_CMD_ELEM(false),
> +		NAND_OP_PARSER_PAT_ADDR_ELEM(false, MAX_ADDR_CYC),
> +		NAND_OP_PARSER_PAT_DATA_IN_ELEM(false, 8)),

Please use the definition used above                   ^

> +	NAND_OP_PARSER_PATTERN(
> +		ls1x_nand_erase_exec,
> +		NAND_OP_PARSER_PAT_CMD_ELEM(false),
> +		NAND_OP_PARSER_PAT_ADDR_ELEM(false, MAX_ADDR_CYC),
> +		NAND_OP_PARSER_PAT_CMD_ELEM(false),
> +		NAND_OP_PARSER_PAT_WAITRDY_ELEM(false)),
> +	NAND_OP_PARSER_PATTERN(
> +		ls1x_nand_read_exec,
> +		NAND_OP_PARSER_PAT_CMD_ELEM(false),
> +		NAND_OP_PARSER_PAT_ADDR_ELEM(false, MAX_ADDR_CYC),
> +		NAND_OP_PARSER_PAT_CMD_ELEM(false),
> +		NAND_OP_PARSER_PAT_WAITRDY_ELEM(true),
> +		NAND_OP_PARSER_PAT_DATA_IN_ELEM(false, 0)),
> +	NAND_OP_PARSER_PATTERN(
> +		ls1x_nand_write_exec,
> +		NAND_OP_PARSER_PAT_CMD_ELEM(false),
> +		NAND_OP_PARSER_PAT_ADDR_ELEM(false, MAX_ADDR_CYC),
> +		NAND_OP_PARSER_PAT_DATA_OUT_ELEM(false, 0),
> +		NAND_OP_PARSER_PAT_CMD_ELEM(false),
> +		NAND_OP_PARSER_PAT_WAITRDY_ELEM(true)),
> +	NAND_OP_PARSER_PATTERN(
> +		ls1x_nand_read_status_exec,
> +		NAND_OP_PARSER_PAT_CMD_ELEM(false),
> +		NAND_OP_PARSER_PAT_DATA_IN_ELEM(false, 1)),
> +	);
> +
> +static int ls1x_nand_exec_op(struct nand_chip *chip,
> +			     const struct nand_operation *op, bool check_only)
> +{
> +	return nand_op_parser_exec_op(chip, &ls1x_nand_op_parser, op,
> +				      check_only);
> +}
> +
> +static int ls1x_nand_read_subpage(struct nand_chip *chip,
> +				  unsigned int data_offs, unsigned int readlen,
> +				  unsigned char *bufpoi, int page)
> +{

There is nothing specific to your controller in that helper, why do you
need it?

> +	struct mtd_info *mtd = nand_to_mtd(chip);
> +	int start_step, end_step, num_steps, ret;
> +	char *p;
> +	int data_col_addr, i;
> +	int datafrag_len, eccfrag_len, aligned_len, aligned_pos;
> +	int busw = (chip->options & NAND_BUSWIDTH_16) ? 2 : 1;
> +	int index, section = 0;
> +	unsigned int max_bitflips = 0;
> +	struct mtd_oob_region oobregion = { };
> +
> +	/* Read the whole page and OOB data */
> +	ret = chip->ecc.read_page_raw(chip, bufpoi, 1, page);
> +	if (ret)
> +		return ret;
> +
> +	/* Column address within the page aligned to ECC size (256bytes) */
> +	start_step = data_offs / chip->ecc.size;
> +	end_step = (data_offs + readlen - 1) / chip->ecc.size;
> +	num_steps = end_step - start_step + 1;
> +	index = start_step * chip->ecc.bytes;
> +
> +	/* Data size aligned to ECC ecc.size */
> +	datafrag_len = num_steps * chip->ecc.size;
> +	eccfrag_len = num_steps * chip->ecc.bytes;
> +
> +	data_col_addr = start_step * chip->ecc.size;
> +	/* If we read not a page aligned data */
> +	p = bufpoi + data_col_addr;
> +
> +	/* Calculate ECC */
> +	for (i = 0; i < eccfrag_len; i += chip->ecc.bytes, p += chip->ecc.size)
> +		chip->ecc.calculate(chip, p, &chip->ecc.calc_buf[i]);
> +
> +	ret = mtd_ooblayout_find_eccregion(mtd, index, &section, &oobregion);
> +	if (ret)
> +		return ret;
> +
> +	aligned_pos = oobregion.offset & ~(busw - 1);
> +	aligned_len = eccfrag_len;
> +	if (oobregion.offset & (busw - 1))
> +		aligned_len++;
> +	if ((oobregion.offset + (num_steps * chip->ecc.bytes)) & (busw - 1))
> +		aligned_len++;
> +
> +	memcpy(&chip->oob_poi[aligned_pos],
> +	       bufpoi + mtd->writesize + aligned_pos, aligned_len);
> +
> +	ret = mtd_ooblayout_get_eccbytes(mtd, chip->ecc.code_buf,
> +					 chip->oob_poi, index, eccfrag_len);
> +	if (ret)
> +		return ret;
> +
> +	p = bufpoi + data_col_addr;
> +	for (i = 0; i < eccfrag_len; i += chip->ecc.bytes, p += chip->ecc.size) {
> +		int stat;
> +
> +		stat = chip->ecc.correct(chip, p, &chip->ecc.code_buf[i],
> +					 &chip->ecc.calc_buf[i]);
> +		if (stat)
> +			ls1x_nand_dump_regs(chip);
> +
> +		if (stat == -EBADMSG &&
> +		    (chip->ecc.options & NAND_ECC_GENERIC_ERASED_CHECK)) {
> +			/* check for empty pages with bitflips */
> +			stat = nand_check_erased_ecc_chunk(p, chip->ecc.size,
> +							&chip->ecc.code_buf[i],
> +							chip->ecc.bytes,
> +							NULL, 0,
> +							chip->ecc.strength);
> +		}
> +
> +		if (stat < 0) {
> +			mtd->ecc_stats.failed++;
> +		} else {
> +			mtd->ecc_stats.corrected += stat;
> +			max_bitflips = max_t(unsigned int, max_bitflips, stat);
> +		}
> +	}
> +	return max_bitflips;
> +}
> +
> +static int ls1x_nand_attach_chip(struct nand_chip *chip)
> +{
> +	struct ls1x_nand *nand = nand_get_controller_data(chip);
> +	struct ls1x_nand_controller *nc = &nand->nc;
> +	struct plat_ls1x_nand *pdata = nand->pdata;
> +	int hold_cycle = pdata->hold_cycle;
> +	int wait_cycle = pdata->wait_cycle;
> +	u64 chipsize = nanddev_target_size(&chip->base);
> +	int cell_size = 0;
> +

You should somehow be able to configure the controller to work in
software mode or without ECC for debug purposes. Please add and test
those two features.

> +	switch (chipsize) {
> +	case SZ_128M:
> +		cell_size = 0x0;
> +		break;
> +	case SZ_256M:
> +		cell_size = 0x1;
> +		break;
> +	case SZ_512M:
> +		cell_size = 0x2;
> +		break;
> +	case SZ_1G:
> +		cell_size = 0x3;
> +		break;
> +	case SZ_2G:
> +		cell_size = 0x4;
> +		break;
> +	case SZ_4G:
> +		cell_size = 0x5;
> +		break;
> +	case (SZ_2G * SZ_4G):	/*8G */
> +		cell_size = 0x6;
> +		break;
> +	case (SZ_4G * SZ_4G):	/*16G */
> +		cell_size = 0x7;
> +		break;
> +	default:
> +		dev_err(nand->dev, "unsupported chip size: %llu MB\n",
> +			chipsize);
> +		break;
> +	}
> +
> +	if (hold_cycle && wait_cycle)
> +		nand_writel(nc, NAND_TIMING,
> +			    (hold_cycle << BITS_PER_BYTE) | wait_cycle);
> +	nand_writel(nc, NAND_PARAM,
> +		    (nand_readl(nc, NAND_PARAM) & ~SIZE_MASK) | cell_size <<
> +		    BITS_PER_BYTE);

Please do this in three steps for readability:

param = nand_readl()
param |= cell_size...
nand_writel()

> +
> +	chip->ecc.read_page_raw = nand_monolithic_read_page_raw;
> +	chip->ecc.write_page_raw = nand_monolithic_write_page_raw;

Nice :)

> +
> +	return 0;
> +}
> +
> +static const struct nand_controller_ops ls1x_nc_ops = {
> +	.exec_op = ls1x_nand_exec_op,
> +	.attach_chip = ls1x_nand_attach_chip,
> +};
> +
> +static void ls1x_nand_controller_cleanup(struct ls1x_nand *nand)
> +{
> +	if (nand->nc.dma_chan)
> +		dma_release_channel(nand->nc.dma_chan);
> +}
> +
> +static int ls1x_nand_controller_init(struct ls1x_nand *nand,
> +				     struct platform_device *pdev)
> +{
> +	struct ls1x_nand_controller *nc = &nand->nc;
> +	struct device *dev = &pdev->dev;
> +	struct dma_slave_config cfg;
> +	struct resource *res;
> +	int ret;
> +
> +	nc->reg_base = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(nc->reg_base))
> +		return PTR_ERR(nc->reg_base);
> +
> +	res = platform_get_resource(pdev, IORESOURCE_DMA, 0);
> +	if (!res) {
> +		dev_err(dev, "failed to get DMA information!\n");
> +		return -ENXIO;
> +	}
> +
> +	nc->dma_chan = dma_request_chan(dev, res->name);
> +	if (!nc->dma_chan) {
> +		dev_err(dev, "failed to request DMA channel!\n");
> +		return -EBUSY;
> +	}
> +	dev_info(dev, "got %s for %s access\n",
> +		 dma_chan_name(nc->dma_chan), dev_name(dev));
> +
> +	cfg.src_addr = CPHYSADDR(nc->reg_base + NAND_DMA_ADDR);
> +	cfg.dst_addr = CPHYSADDR(nc->reg_base + NAND_DMA_ADDR);
> +	cfg.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
> +	cfg.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
> +	ret = dmaengine_slave_config(nc->dma_chan, &cfg);
> +	if (ret) {
> +		dev_err(dev, "failed to config DMA channel!\n");
> +		dma_release_channel(nc->dma_chan);
> +		return ret;
> +	}
> +
> +	init_completion(&nc->dma_complete);
> +
> +	return 0;
> +}
> +
> +static int ls1x_nand_chip_init(struct ls1x_nand *nand)
> +{
> +	struct nand_chip *chip = &nand->chip;
> +	struct mtd_info *mtd = nand_to_mtd(chip);
> +	struct plat_ls1x_nand *pdata = nand->pdata;
> +	int ret = 0;
> +
> +	chip->controller = &nand->controller;
> +	chip->options = NAND_NO_SUBPAGE_WRITE | NAND_USES_DMA | NAND_BROKEN_XD;
> +	chip->buf_align = 16;
> +	chip->ecc.engine_type = NAND_ECC_ENGINE_TYPE_SOFT;
> +	chip->ecc.algo = NAND_ECC_ALGO_HAMMING;

ECC configuration should only be done in ->attach_chip().

> +	nand_set_controller_data(chip, nand);
> +
> +	mtd->dev.parent = nand->dev;
> +	mtd->name = "ls1x-nand";
> +	mtd->owner = THIS_MODULE;
> +
> +	ret = nand_scan(chip, 1);
> +	if (ret)
> +		return ret;
> +
> +	chip->ecc.read_subpage = ls1x_nand_read_subpage;

Do you really need this? It looks like your implementation of
read_subpage is very similar to the one from the core.

> +
> +	ret = mtd_device_register(mtd, pdata->parts, pdata->nr_parts);
> +	if (ret) {
> +		dev_err(nand->dev, "failed to register MTD device! %d\n", ret);
> +		nand_cleanup(chip);
> +	}
> +
> +	return ret;
> +}
> +
> +static int ls1x_nand_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct plat_ls1x_nand *pdata;
> +	struct ls1x_nand *nand;

Please use another name for the variable, "nand"/"chip" is used by the
core for the nand_chip structure, for yours you can name it eg ls1x or
lsnand.

> +	int ret;
> +
> +	pdata = dev_get_platdata(dev);
> +	if (!pdata) {
> +		dev_err(dev, "platform data missing!\n");
> +		return -EINVAL;
> +	}
> +
> +	nand = devm_kzalloc(dev, sizeof(*nand), GFP_KERNEL);
> +	if (!nand)
> +		return -ENOMEM;
> +
> +	nand->pdata = pdata;
> +	nand->dev = dev;
> +	nand->controller.ops = &ls1x_nc_ops;
> +	nand_controller_init(&nand->controller);
> +
> +	ret = ls1x_nand_controller_init(nand, pdev);

I'm not sure this deserves a helper (same for the chip init) but why
not.

> +	if (ret)
> +		return ret;
> +
> +	nand->clk = devm_clk_get(dev, pdev->name);
> +	if (IS_ERR(nand->clk)) {
> +		dev_err(dev, "failed to get %s clock!\n", pdev->name);
> +		return PTR_ERR(nand->clk);
> +	}
> +	clk_prepare_enable(nand->clk);
> +
> +	ret = ls1x_nand_chip_init(nand);
> +	if (ret) {
> +		clk_disable_unprepare(nand->clk);
> +		goto err;
> +	}
> +
> +	platform_set_drvdata(pdev, nand);
> +	dev_info(dev, "Loongson1 NAND driver registered\n");

I don't think this is useful, you can drop that trace.

> +
> +	return 0;
> +err:
> +	ls1x_nand_controller_cleanup(nand);
> +	return ret;
> +}
> +
> +static int ls1x_nand_remove(struct platform_device *pdev)
> +{
> +	struct ls1x_nand *nand = platform_get_drvdata(pdev);
> +	struct nand_chip *chip = &nand->chip;
> +
> +	mtd_device_unregister(nand_to_mtd(chip));

ret = mtd_device_unregister()
WARN_ON(ret);

> +	nand_cleanup(chip);
> +	clk_disable_unprepare(nand->clk);
> +	ls1x_nand_controller_cleanup(nand);
> +
> +	return 0;
> +}
> +
> +static struct platform_driver ls1x_nand_driver = {
> +	.probe	= ls1x_nand_probe,
> +	.remove	= ls1x_nand_remove,
> +	.driver	= {
> +		.name	= "ls1x-nand",

ls1x-nand-controller

> +		.owner	= THIS_MODULE,
> +	},
> +};
> +
> +module_platform_driver(ls1x_nand_driver);
> +
> +MODULE_AUTHOR("Kelvin Cheung <keguang.zhang@gmail.com>");
> +MODULE_DESCRIPTION("Loongson1 NAND Flash driver");
> +MODULE_LICENSE("GPL");
> 
> base-commit: fd0d8d85f7230052e638a56d1bfea170c488e6bc




Thanks,
Miquèl