4.4-stable review patch. If anyone has any objections, please let me know.
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From: Markus Pargmann mpa@pengutronix.de
commit bd2e778c9ee361c23ccb2b10591712e129d97893 upstream.
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.
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 Cc: Sascha Hauer s.hauer@pengutronix.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/mtd/nand/gpmi-nand/gpmi-nand.c | 78 ++++++++++++++++++++++++++++++--- 1 file changed, 73 insertions(+), 5 deletions(-)
--- 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 /* 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 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; }