linux-kernel - Re: [PATCH v11 2/5] mtd: nand: vf610

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Date:	Tue, 01 Sep 2015 09:55:48 -0700
From:	Stefan Agner <stefan@...er.ch>
To:	computersforpeace@...il.com
Cc:	sebastian@...akpoint.cc, robh+dt@...nel.org, pawel.moll@....com,
	mark.rutland@....com, ijc+devicetree@...lion.org.uk,
	galak@...eaurora.org, shawn.guo@...aro.org, kernel@...gutronix.de,
	boris.brezillon@...e-electrons.com, marb@...at.de,
	aaron@...tycactus.com, bpringlemeir@...il.com,
	linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	albert.aribaud@...ev.fr, klimov.linux@...il.com,
	Bill Pringlemeir <bpringlemeir@...ps.com>
Subject: Re: [PATCH v11 2/5] mtd: nand: vf610_nfc: add hardware BCH-ECC
 support

On 2015-08-27 17:34, Stefan Agner wrote:
> +static inline int vf610_nfc_correct_data(struct mtd_info *mtd, uint8_t *dat,
> +					 uint8_t *oob, int page)
> +{
> +	struct vf610_nfc *nfc = mtd_to_nfc(mtd);
> +	u32 ecc_status_off = NFC_MAIN_AREA(0) + ECC_SRAM_ADDR + ECC_STATUS;
> +	u8 ecc_status;
> +	u8 ecc_count;
> +	int flips;
> +	int flips_threshold = nfc->chip.ecc.strength / 2;
> +
> +	ecc_status = vf610_nfc_read(nfc, ecc_status_off) & 0xff;
> +	ecc_count = ecc_status & ECC_STATUS_ERR_COUNT;
> +
> +	if (!(ecc_status & ECC_STATUS_MASK))
> +		return ecc_count;
> +
> +	/* Read OOB without ECC unit enabled */
> +	vf610_nfc_command(mtd, NAND_CMD_READOOB, 0, page);
> +	vf610_nfc_read_buf(mtd, oob, mtd->oobsize);
> +
> +	/*
> +	 * On an erased page, bit count (including OOB) should be zero or
> +	 * at least less then half of the ECC strength.
> +	 */
> +	flips = count_written_bits(dat, nfc->chip.ecc.size, flips_threshold);
> +	flips += count_written_bits(oob, mtd->oobsize, flips_threshold);
> +
> +	if (unlikely(flips > flips_threshold))
> +		return -EINVAL;
> +
> +	/* Erased page. */
> +	memset(dat, 0xff, nfc->chip.ecc.size);
> +	memset(oob, 0xff, mtd->oobsize);
> +	return 0;

I guess I should return the amount of bitflips here. Will send out a v12
today.

--
Stefan
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