linux-kernel - Re: [PATCH v7 2/2] mtd: rawnand: nuvoton: add new driver for the Nuvoton MA35 SoC

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Message-ID: <ZxItGw0m_w0jgtAq@pengutronix.de>
Date: Fri, 18 Oct 2024 11:40:43 +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,
	nikita.shubin@...uefel.me, arnd@...db.de, vkoul@...nel.org,
	esben@...nix.com, linux-arm-kernel@...ts.infradead.org,
	linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 2/2] mtd: rawnand: nuvoton: add new driver for the
 Nuvoton MA35 SoC

On Fri, Oct 18, 2024 at 02:25:19AM +0000, Hui-Ping Chen wrote:
> +static int ma35_nfi_ecc_check(struct nand_chip *chip, u8 *addr)
> +{
> +	struct ma35_nand_info *nand = nand_get_controller_data(chip);
> +	struct mtd_info *mtd = nand_to_mtd(chip);
> +	int i, j, nchunks = 0;
> +	int report_err = 0;
> +	int err_cnt = 0;
> +	u32 status;
> +
> +	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) == 0x01) {
> +				/* Correctable error */
> +				err_cnt = (status >> 2) & ECC_ERR_CNT_MASK;
> +				ma35_nfi_correct(chip, j * 4 + i, err_cnt, addr);
> +				report_err += err_cnt;

This is still wrong. This should be

				report_err = max(report_err, err_cnt);

You have to search for the subpage that has the most bitflips and return
the number of bitflips on that subpage, *not* the total amount of errors
on the whole page.

That said, the statistic counter should still count the total number of
bitflips occurred.

Sascha

> +			} else {
> +				/* Uncorrectable error */
> +				dev_warn(nand->dev, "uncorrectable error! 0x%4x\n", status);
> +				return -EBADMSG;
> +			}
> +			status >>= 8;
> +		}
> +	}
> +	return report_err;
> +}
> +

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