From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-gw2-out.broadcom.com ([216.31.210.63]) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1awEv5-0007Rk-Ip for linux-mtd@lists.infradead.org; Fri, 29 Apr 2016 20:21:48 +0000 From: Kamal Dasu To: linux-mtd@lists.infradead.org, computersforpeace@gmail.com Cc: f.fainelli@gmail.com, bcm-kernel-feedback-list@broadcom.com, Kamal Dasu Subject: [PATCH 1/2] mtd: brcmnand: Add check for erased page bitflips Date: Fri, 29 Apr 2016 16:21:24 -0400 Message-Id: <1461961285-24159-1-git-send-email-kdasu.kdev@gmail.com> List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Check for erased page bitflips in a page. And if well within threshold return data as all 0xff. Signed-off-by: Kamal Dasu --- drivers/mtd/nand/brcmnand/brcmnand.c | 83 +++++++++++++++++++++++++++++++++--- 1 file changed, 78 insertions(+), 5 deletions(-) diff --git a/drivers/mtd/nand/brcmnand/brcmnand.c b/drivers/mtd/nand/brcmnand/brcmnand.c index e052839..29a9abd 100644 --- a/drivers/mtd/nand/brcmnand/brcmnand.c +++ b/drivers/mtd/nand/brcmnand/brcmnand.c @@ -1490,6 +1490,64 @@ static int brcmnand_read_by_pio(struct mtd_info *mtd, struct nand_chip *chip, return ret; } +/* + * Check a page to see if it is erased (w/ bitflips) after an uncorrectable ECC + * error + * + * Because the HW ECC signals an ECC error if an erase paged has even a single + * bitflip, we must check each ECC error to see if it is actually an erased + * page with bitflips, not a truly corrupted page. + * + * On a real error, return a negative error code (-EBADMSG for ECC error), and + * buf will contain raw data. + * Otherwise, fill buf with 0xff and return the maximum number of + * bitflips-per-ECC-sector to the caller. + * + */ +static int brcmstb_nand_verify_erased_page(struct mtd_info *mtd, + struct nand_chip *chip, void *buf, u64 addr) +{ + int i, sas, oob_nbits, data_nbits; + void *oob = chip->oob_poi; + unsigned int max_bitflips = 0; + int page = addr >> chip->page_shift; + int ret; + + if (!buf) { + buf = chip->buffers->databuf; + /* Invalidate page cache */ + chip->pagebuf = -1; + } + + sas = mtd->oobsize / chip->ecc.steps; + oob_nbits = sas << 3; + data_nbits = chip->ecc.size << 3; + + /* read without ecc for verification */ + chip->cmdfunc(mtd, NAND_CMD_READ0, 0x00, page); + ret = chip->ecc.read_page_raw(mtd, chip, buf, true, page); + if (ret) + return ret; + + for (i = 0; i < chip->ecc.steps; i++, oob += sas) { + unsigned int bitflips = 0; + + bitflips += oob_nbits - bitmap_weight(oob, oob_nbits); + bitflips += data_nbits - bitmap_weight(buf, data_nbits); + + buf += chip->ecc.size; + addr += chip->ecc.size; + + /* Too many bitflips */ + if (bitflips > chip->ecc.strength) + return -EBADMSG; + + max_bitflips = max(max_bitflips, bitflips); + } + + return max_bitflips; +} + static int brcmnand_read(struct mtd_info *mtd, struct nand_chip *chip, u64 addr, unsigned int trans, u32 *buf, u8 *oob) { @@ -1520,11 +1578,26 @@ static int brcmnand_read(struct mtd_info *mtd, struct nand_chip *chip, } if (mtd_is_eccerr(err)) { - dev_dbg(ctrl->dev, "uncorrectable error at 0x%llx\n", - (unsigned long long)err_addr); - mtd->ecc_stats.failed++; - /* NAND layer expects zero on ECC errors */ - return 0; + int ret; + + ret = brcmstb_nand_verify_erased_page(mtd, chip, buf, addr); + if (ret < 0) { + dev_dbg(ctrl->dev, "uncorrectable error at 0x%llx\n", + (unsigned long long)err_addr); + mtd->ecc_stats.failed++; + /* NAND layer expects zero on ECC errors */ + return 0; + } else { + if (buf) + memset(buf, 0xff, FC_BYTES * trans); + if (oob) + memset(oob, 0xff, mtd->oobsize); + + dev_info(&host->pdev->dev, + "corrected %d bitflips in blank page at 0x%llx\n", + ret, (unsigned long long)addr); + return ret; + } } if (mtd_is_bitflip(err)) { -- 1.9.1