Message-ID: <ZuqyRXi-LWZ7-Qgw@pengutronix.de>
Date: Wed, 18 Sep 2024 12:58:13 +0200
From: Sascha Hauer <s.hauer@...gutronix.de>
To: Hui-Ping Chen <hpchen0nvt@...il.com>
Cc: miquel.raynal@...tlin.com, richard@....at, vigneshr@...com,
	robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
	sumit.semwal@...aro.org, christian.koenig@....com, esben@...nix.com,
	linux-arm-kernel@...ts.infradead.org, linux-mtd@...ts.infradead.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH v4 2/2] mtd: rawnand: nuvoton: add new driver for the
 Nuvoton MA35 SoC

Hi,

The driver has a few minor whitespace issues, please run through
checkpatch.pl to catch them.

Some more things inline.

On Wed, Sep 18, 2024 at 09:03:08AM +0000, Hui-Ping Chen wrote:
> Nuvoton MA35 SoCs NAND Flash Interface Controller
> supports 2kiB, 4kiB and 8kiB page size, and up to
> 8-bit, 12-bit, and 24-bit hardware ECC calculation
> circuit to protect data.
> 
> Signed-off-by: Hui-Ping Chen <hpchen0nvt@...il.com>
> ---
>  drivers/mtd/nand/raw/Kconfig               |   8 +
>  drivers/mtd/nand/raw/Makefile              |   1 +
>  drivers/mtd/nand/raw/nuvoton_ma35d1_nand.c | 935 +++++++++++++++++++++
>  3 files changed, 944 insertions(+)
>  create mode 100644 drivers/mtd/nand/raw/nuvoton_ma35d1_nand.c
> 
> +#define SKIP_SPARE_BYTES	4

Unused, please drop.

> +static int ma35_nfi_ecc_check(struct nand_chip *chip, unsigned long addr)
> +{
> +	struct ma35_nand_info *nand = nand_get_controller_data(chip);
> +	struct mtd_info *mtd = nand_to_mtd(chip);
> +	int status, i, j, nchunks = 0;

status should be unsigned.

> +	int report_err = 0;
> +	int err_cnt = 0;
> +
> +	nchunks = mtd->writesize / chip->ecc.steps;
> +	if (nchunks < 4)
> +		nchunks = 1;
> +	else
> +		nchunks /= 4;
> +
> +	for (j = 0; j < nchunks; j++) {
> +		status = readl(nand->regs + MA35_NFI_REG_NANDECCES0 + j*4);
> +		if (!status)
> +			continue;
> +
> +		for (i = 0; i < 4; i++) {
> +			if (!(status & ECC_STATUS_MASK)) {
> +				/* No error */
> +				status >>= 8;
> +				continue;
> +
> +			} else if ((status & ECC_STATUS_MASK) == 0x01) {
> +				/* Correctable error */
> +				err_cnt = (status >> 2) & ECC_ERR_CNT_MASK;
> +				dev_warn(nand->dev, "nchunks (%d, %d) have %d error!\n",
> +					j, i, err_cnt);

Correctable bitflips are expected. Please don't spam the log with it.

> +				ma35_nfi_correct(nand, j*4+i, err_cnt, (u8 *)addr);
> +				report_err += err_cnt;
> +
> +			} else {
> +				/* uncorrectable error */
> +				dev_warn(nand->dev, "uncorrectable error! 0x%4x\n", status);
> +				return -1;
> +			}
> +			status >>= 8;
> +		}
> +	}
> +	return report_err;

There are a few things wrong here. Your chip->ecc.read_page op must
return the maximum number of bitflips occured on a subpage while
reading a page.

To archieve this I suggest you fix the return value of this function
accordingly and call it from chip->ecc.read_page rather than from the
interrupt handler.

Nevertheless mtd->ecc_stats.corrected counts the total number of
bitflips, so you must handle this counter in this function.

See rk_nfc_read_page_hwecc() as an example of a driver which gets it
right.

The background is that we have to rewrite the page once one ECC block
hits a critical bitflip limit. A whole page might be fine when the
bitflips are evenly distributed across the subpages, but it's not when
all bitflips are occur in a single subpage.

> +static int ma35_nand_do_write(struct nand_chip *chip, const u8 *addr, u32 len)
> +{
> +	struct ma35_nand_info *nand = nand_get_controller_data(chip);
> +	struct mtd_info *mtd = nand_to_mtd(chip);
> +	dma_addr_t dma_addr;
> +	int ret = 0, i;
> +	u32 val, reg;
> +
> +	ma35_nand_target_enable(nand);
> +
> +	if (len != mtd->writesize) {
> +		for (i = 0; i < len; i++)
> +			writel(addr[i], nand->regs + MA35_NFI_REG_NANDDATA);
> +		ma35_nand_target_disable(nand);
> +		return ret;
> +	}
> +
> +	/* Check the DMA status before enabling the DMA */
> +	ret = readl_poll_timeout(nand->regs + MA35_NFI_REG_DMACTL, val,
> +				 !(val & DMA_BUSY), 50, HZ/2);
> +	if (ret)
> +		dev_warn(nand->dev, "dma busy\n");
> +
> +	/* Reinitial dmac */
> +	ma35_nand_dmac_init(nand);

The function name already says it and the comment doesn't offer any
additional information. Please drop such comments.

> +
> +	writel(mtd->oobsize, nand->regs + MA35_NFI_REG_NANDRACTL);
> +
> +	/* setup and start DMA using dma_addr */
> +	writel(INT_DMA, nand->regs + MA35_NFI_REG_NANDINTEN);
> +	/* To mark this page as dirty. */
> +	reg = readl(nand->regs + MA35_NFI_REG_NANDRA0);
> +	if (reg & 0xffff0000)
> +		writel(reg & 0xffff, nand->regs + MA35_NFI_REG_NANDRA0);
> +
> +	/* Fill dma_addr */
> +	dma_addr = dma_map_single(nand->dev, (void *)addr, len, DMA_TO_DEVICE);
> +	dma_sync_single_for_device(nand->dev, dma_addr, len, DMA_TO_DEVICE);
> +	ret = dma_mapping_error(nand->dev, dma_addr);
> +	if (ret) {
> +		dev_err(nand->dev, "dma mapping error\n");
> +		return -EINVAL;
> +	}

Call dma_sync_single_for_device() after you have checked for an error
with dma_mapping_error().

That said, I think calling dma_sync_single_for_device() after
dma_map_single() is unnecessary.

> +
> +	writel((unsigned long)dma_addr, nand->regs + MA35_NFI_REG_DMASA);
> +	writel(readl(nand->regs + MA35_NFI_REG_NANDCTL) | DMA_W_EN,
> +		nand->regs + MA35_NFI_REG_NANDCTL);
> +	ret = wait_for_completion_timeout(&nand->complete, msecs_to_jiffies(1000));
> +	if (!ret) {
> +		dev_err(nand->dev, "write timeout\n");
> +		ret = -ETIMEDOUT;
> +	}
> +
> +	dma_unmap_single(nand->dev, dma_addr, len, DMA_TO_DEVICE);
> +
> +	ma35_nand_target_disable(nand);
> +
> +	return ret;
> +}
> +
> +static int ma35_nand_do_read(struct nand_chip *chip, const u8 *addr, u32 len)

The addr argument shouldn't be const. You are supposed to write to this
buffer and you actually do so.

> +{
> +	struct ma35_nand_info *nand = nand_get_controller_data(chip);
> +	struct mtd_info *mtd = nand_to_mtd(chip);
> +	u8 *ptr = (u8 *)addr;
> +	dma_addr_t dma_addr;
> +	int ret = 0, i;
> +	u32 val;
> +
> +	ma35_nand_target_enable(nand);
> +
> +	if (len != mtd->writesize) {
> +		for (i = 0; i < len; i++)
> +			*(ptr+i) = (u8)readl(nand->regs + MA35_NFI_REG_NANDDATA);
> +		ma35_nand_target_disable(nand);
> +		return ret;

Just return 0 here. It's easier to read than having to look up the
initialization value.

> +	}
> +
> +	/* Check the DMA status before enabling the DMA */
> +	ret = readl_poll_timeout(nand->regs + MA35_NFI_REG_DMACTL, val,
> +				 !(val & DMA_BUSY), 50, HZ/2);
> +	if (ret)
> +		dev_warn(nand->dev, "dma busy\n");
> +
> +	/* Reinitial dmac */
> +	ma35_nand_dmac_init(nand);
> +
> +	writel(mtd->oobsize, nand->regs + MA35_NFI_REG_NANDRACTL);
> +
> +	/* setup and start DMA using dma_addr */
> +	dma_addr = dma_map_single(nand->dev, (void *)addr, len, DMA_FROM_DEVICE);
> +	ret = dma_mapping_error(nand->dev, dma_addr);
> +	if (ret) {
> +		dev_err(nand->dev, "dma mapping error\n");
> +		return -EINVAL;
> +	}
> +	nand->dma_buf = (u8 *)addr;
> +	nand->dma_addr = dma_addr;
> +
> +	writel((unsigned long)dma_addr, nand->regs + MA35_NFI_REG_DMASA);
> +	writel(readl(nand->regs + MA35_NFI_REG_NANDCTL) | DMA_R_EN,
> +		nand->regs + MA35_NFI_REG_NANDCTL);
> +	ret = wait_for_completion_timeout(&nand->complete, msecs_to_jiffies(1000));
> +	if (!ret) {
> +		dev_err(nand->dev, "read timeout\n");
> +		ret = -ETIMEDOUT;
> +	}
> +
> +	dma_sync_single_for_cpu(nand->dev, dma_addr, len, DMA_FROM_DEVICE);
> +	dma_unmap_single(nand->dev, dma_addr, len, DMA_FROM_DEVICE);

No need to call dma_sync_single_for_cpu() before dma_unmap_single().

> +
> +	ma35_nand_target_disable(nand);
> +
> +	return ret;
> +}
> +
> +
> +static int ma35_nand_write_page_hwecc(struct nand_chip *chip, const u8 *buf,
> +				      int oob_required, int page)
> +{
> +	struct mtd_info *mtd = nand_to_mtd(chip);
> +	u8 *ecc_calc = chip->ecc.calc_buf;

Make this a void * to get rid of the explicit casting below.

> +
> +	ma35_clear_spare(chip, mtd->oobsize);
> +	ma35_write_spare(chip, mtd->oobsize - chip->ecc.total, (u32 *)chip->oob_poi);
> +
> +	nand_prog_page_begin_op(chip, page, 0, buf, mtd->writesize);
> +	nand_prog_page_end_op(chip);
> +
> +	/* Copy parity code in NANDRA to calc */
> +	ma35_read_spare(chip, chip->ecc.total, (u32 *)ecc_calc,
> +			mtd->oobsize - chip->ecc.total);
> +
> +	/* Copy parity code in calc to oob_poi */
> +	memcpy((void *)(chip->oob_poi + (mtd->oobsize - chip->ecc.total)),
> +		(void *)ecc_calc, chip->ecc.total);
> +
> +	return 0;
> +}
> +
> +static irqreturn_t ma35_nand_irq(int irq, void *id)
> +{
> +	struct ma35_nand_info *nand = (struct ma35_nand_info *)id;
> +	struct mtd_info *mtd = nand_to_mtd(&nand->chip);
> +	int stat = 0;
> +	u32 isr;
> +
> +	spin_lock(&nand->dma_lock);
> +
> +	isr = readl(nand->regs + MA35_NFI_REG_NANDINTSTS);
> +	if (isr & INT_ECC) {
> +		dma_sync_single_for_cpu(nand->dev, nand->dma_addr, mtd->writesize,
> +					DMA_FROM_DEVICE);
> +		stat = ma35_nfi_ecc_check(&nand->chip, (unsigned long)nand->dma_buf);

nand->dma_buf already is a pointer which you cast to unisgned long here
and back to a pointer in ma35_nfi_ecc_check(). ma35_nfi_ecc_check()
should take a poiner instead.

> +		if (stat < 0) {
> +			mtd->ecc_stats.failed++;
> +			writel(DMA_RST | DMA_EN, nand->regs + MA35_NFI_REG_DMACTL);
> +			writel(readl(nand->regs + MA35_NFI_REG_NANDCTL) | SWRST,
> +				nand->regs + MA35_NFI_REG_NANDCTL);
> +		} else if (stat > 0) {
> +			mtd->ecc_stats.corrected += stat;   /* Add corrected bit count */
> +		}
> +		writel(INT_ECC, nand->regs + MA35_NFI_REG_NANDINTSTS);
> +	}
> +	if (isr & INT_DMA) {
> +		writel(INT_DMA, nand->regs + MA35_NFI_REG_NANDINTSTS);
> +		complete(&nand->complete);
> +	}
> +	spin_unlock(&nand->dma_lock);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int ma35_nfc_exec_op(struct nand_chip *chip,
> +			  const struct nand_operation *op,
> +			  bool check_only)
> +{
> +	struct ma35_nand_info *nand = nand_get_controller_data(chip);
> +	u32 i, reg;
> +	int ret = 0;
> +
> +	if (check_only)
> +		return 0;
> +
> +	ma35_nand_target_enable(nand);
> +	reg = readl(nand->regs + MA35_NFI_REG_NANDINTSTS);
> +	reg |= INT_RB0;
> +	writel(reg, nand->regs + MA35_NFI_REG_NANDINTSTS);
> +
> +	for (i = 0; i < op->ninstrs; i++) {
> +		ret = ma35_nfc_exec_instr(chip, &op->instrs[i]);
> +		if (ret)
> +			break;
> +	}

The way ma35_nand_target_[en|dis]able() is called looks inconsistent.

This function calls ma35_nand_target_enable(), so I would expect that
the corresponding ma35_nand_target_disable() should be called here as
well.

ma35_nand_do_read() is called from here which has its own call to
ma35_nand_target_enable(), but it doesn't call ma35_nand_target_disable()
from all of its return pathes.

> +
> +	ret = devm_request_irq(&pdev->dev, nand->irq, ma35_nand_irq,
> +				  IRQF_TRIGGER_HIGH, "ma35d1-nand", nand);
> +	if (ret) {
> +		dev_err(&pdev->dev, "failed to request NAND irq\n");
> +		clk_disable_unprepare(nand->clk);

You used devm_clk_get_enabled(), so this will be done automatically.

> +		return -ENXIO;
> +	}
> +
> +	nand->chip.controller = &nand->controller;
> +	platform_set_drvdata(pdev, nand);
> +
> +	chip->options |= NAND_NO_SUBPAGE_WRITE | NAND_USES_DMA;
> +
> +	/* set default mode in case dt entry is missing */
> +	chip->ecc.engine_type = NAND_ECC_ENGINE_TYPE_ON_HOST;
> +
> +	chip->ecc.write_page = ma35_nand_write_page_hwecc;
> +	chip->ecc.read_page  = ma35_nand_read_page_hwecc;
> +	chip->ecc.read_oob   = ma35_nand_read_oob_hwecc;
> +
> +	mtd = nand_to_mtd(chip);
> +	mtd->priv = chip;
> +	mtd->owner = THIS_MODULE;
> +	mtd->dev.parent = &pdev->dev;
> +
> +	writel(NAND_EN, nand->regs + MA35_NFI_REG_GCTL);
> +
> +	ret = nand_scan(chip, 1);
> +	if (ret)
> +		return ret;
> +
> +	ret = mtd_device_register(mtd, NULL, 0);
> +	if (ret) {
> +		nand_cleanup(chip);
> +		devm_kfree(&pdev->dev, nand);

Unnecessary free. Drop it.

> +		return ret;
> +	}
> +
> +	return ret;
> +}
> +
> +static void ma35_nand_remove(struct platform_device *pdev)
> +{
> +	struct ma35_nand_info *nand = platform_get_drvdata(pdev);
> +	int ret;
> +
> +	devm_free_irq(&pdev->dev, nand->irq, nand);

devm_ is a mechanism to let resources be freed automatically. There's
normally no need to do this manually.

Sascha

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