The following went into v4.4.120:

197190bc5c48 mtd: nand: gpmi: Fix failure when a erased page has a bitflip at BBM

This patch was backported to far for the stable tree. It only makes sense (and only works) together with:

bd2e778c9ee3 gpmi-nand: Handle ECC Errors in erased pages

which first appeared in v4.7.

So either we revert 197190bc5c48 on the v4.4 stable tree or we apply the attached patch which is a backport of bd2e778c9ee3 for v4.4.

I don't know which solution is prefered, personally I would prefer applying the attached patch which is also a bugfix. Without it erased pages may not be handled properly.

Sascha

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From ec42023a83778e524a024bdd25d970b8dc7a3966 Mon Sep 17 00:00:00 2001

From: Markus Pargmann mpa@pengutronix.de Date: Mon, 25 Apr 2016 14:35:12 +0200 Subject: [PATCH] gpmi-nand: Handle ECC Errors in erased pages

ECC is only calculated for written pages. As erased pages are not actively written the ECC is always invalid. For this purpose the Hardware BCH unit is able to check for erased pages and does not raise an ECC error in this case. This behaviour can be influenced using the BCH_MODE register which sets the number of allowed bitflips in an erased page. Unfortunately the unit is not capable of fixing the bitflips in memory.

To avoid complete software checks for erased pages, we can simply check buffers with uncorrectable ECC errors because we know that any erased page with errors is uncorrectable by the BCH unit.

This patch adds the generic nand_check_erased_ecc_chunk() to gpmi-nand to correct erased pages. To have the valid data in the buffer before using them, this patch moves the read_page_swap_end() call before the ECC status checking for-loop.

Fixes: 197190bc5c48 ("mtd: nand: gpmi: Fix failure when a erased page has a bitflip at BBM") Signed-off-by: Markus Pargmann mpa@pengutronix.de [Squashed patches by Stefan and Boris to check ECC area] Tested-by: Stefan Christ s.christ@phytec.de Acked-by: Han xu han.xu@nxp.com Signed-off-by: Boris Brezillon boris.brezillon@free-electrons.com --- drivers/mtd/nand/gpmi-nand/gpmi-nand.c | 78 ++++++++++++++++++++++++-- 1 file changed, 73 insertions(+), 5 deletions(-)

diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c index e2a239c1f40b..40a335c6b792 100644 --- a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c +++ b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c @@ -1032,14 +1032,87 @@ static int gpmi_ecc_read_page(struct mtd_info *mtd, struct nand_chip *chip, /* Loop over status bytes, accumulating ECC status. */ status = auxiliary_virt + nfc_geo->auxiliary_status_offset;

+ read_page_swap_end(this, buf, nfc_geo->payload_size, + this->payload_virt, this->payload_phys, + nfc_geo->payload_size, + payload_virt, payload_phys); + for (i = 0; i < nfc_geo->ecc_chunk_count; i++, status++) { if ((*status == STATUS_GOOD) || (*status == STATUS_ERASED)) continue;

if (*status == STATUS_UNCORRECTABLE) { + int eccbits = nfc_geo->ecc_strength * nfc_geo->gf_len; + u8 *eccbuf = this->raw_buffer; + int offset, bitoffset; + int eccbytes; + int flips; + + /* Read ECC bytes into our internal raw_buffer */ + offset = nfc_geo->metadata_size * 8; + offset += ((8 * nfc_geo->ecc_chunk_size) + eccbits) * (i + 1); + offset -= eccbits; + bitoffset = offset % 8; + eccbytes = DIV_ROUND_UP(offset + eccbits, 8); + offset /= 8; + eccbytes -= offset; + chip->cmdfunc(mtd, NAND_CMD_RNDOUT, offset, -1); + chip->read_buf(mtd, eccbuf, eccbytes); + + /* + * ECC data are not byte aligned and we may have + * in-band data in the first and last byte of + * eccbuf. Set non-eccbits to one so that + * nand_check_erased_ecc_chunk() does not count them + * as bitflips. + */ + if (bitoffset) + eccbuf[0] |= GENMASK(bitoffset - 1, 0); + + bitoffset = (bitoffset + eccbits) % 8; + if (bitoffset) + eccbuf[eccbytes - 1] |= GENMASK(7, bitoffset); + + /* + * The ECC hardware has an uncorrectable ECC status + * code in case we have bitflips in an erased page. As + * nothing was written into this subpage the ECC is + * obviously wrong and we can not trust it. We assume + * at this point that we are reading an erased page and + * try to correct the bitflips in buffer up to + * ecc_strength bitflips. If this is a page with random + * data, we exceed this number of bitflips and have a + * ECC failure. Otherwise we use the corrected buffer. + */ + if (i == 0) { + /* The first block includes metadata */ + flips = nand_check_erased_ecc_chunk( + buf + i * nfc_geo->ecc_chunk_size, + nfc_geo->ecc_chunk_size, + eccbuf, eccbytes, + auxiliary_virt, + nfc_geo->metadata_size, + nfc_geo->ecc_strength); + } else { + flips = nand_check_erased_ecc_chunk( + buf + i * nfc_geo->ecc_chunk_size, + nfc_geo->ecc_chunk_size, + eccbuf, eccbytes, + NULL, 0, + nfc_geo->ecc_strength); + } + + if (flips > 0) { + max_bitflips = max_t(unsigned int, max_bitflips, + flips); + mtd->ecc_stats.corrected += flips; + continue; + } + mtd->ecc_stats.failed++; continue; } + mtd->ecc_stats.corrected += *status; max_bitflips = max_t(unsigned int, max_bitflips, *status); } @@ -1062,11 +1135,6 @@ static int gpmi_ecc_read_page(struct mtd_info *mtd, struct nand_chip *chip, chip->oob_poi[0] = ((uint8_t *) auxiliary_virt)[0]; }

- read_page_swap_end(this, buf, nfc_geo->payload_size, - this->payload_virt, this->payload_phys, - nfc_geo->payload_size, - payload_virt, payload_phys); - return max_bitflips; }