From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ea0-x22b.google.com ([2a00:1450:4013:c01::22b]) by merlin.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1VsGgX-0000z0-KM for linux-mtd@lists.infradead.org; Sun, 15 Dec 2013 18:45:02 +0000 Received: by mail-ea0-f171.google.com with SMTP id h10so1796629eak.16 for ; Sun, 15 Dec 2013 10:44:39 -0800 (PST) From: Elie De Brauwer To: b32955@freescale.com, dwmw2@infradead.org, dedekind1@gmail.com, computersforpeace@gmail.com Subject: [PATCH v2] mtd: gpmi: Deal with bitflips in erased regions regions Date: Sun, 15 Dec 2013 19:44:21 +0100 Message-Id: <1387133061-6573-2-git-send-email-eliedebrauwer@gmail.com> In-Reply-To: <1387133061-6573-1-git-send-email-eliedebrauwer@gmail.com> References: <1387133061-6573-1-git-send-email-eliedebrauwer@gmail.com> Cc: Elie De Brauwer , linux-mtd@lists.infradead.org List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , The BCH block typically used with a i.MX28 and GPMI block is only able to correct bitflips on data actually streamed through the block. When erasing a block the data does not stream through the BCH block and therefore no ECC data is written to the NAND chip. This causes gpmi_ecc_read_page to return failure as soon as a single non-1-bit is found in an erased page. Typically causing problems at higher levels (ubifs corrupted empty space warnings). This patch configures the BCH block to mark a block as 'erased' if no more than ecc_strength bitflips are found. Next HW_BCH_STATUS0:ALLONES is used to check if the data read were all ones. If this was not the case a slow path is entered where bitflips are counted and corrected in software, allowing the upper layers to take proper actions. Signed-off-by: Elie De Brauwer Acked-by: Peter Korsgaard --- drivers/mtd/nand/gpmi-nand/bch-regs.h | 2 ++ drivers/mtd/nand/gpmi-nand/gpmi-lib.c | 17 +++++++++++++ drivers/mtd/nand/gpmi-nand/gpmi-nand.c | 43 +++++++++++++++++++++++++++++--- drivers/mtd/nand/gpmi-nand/gpmi-nand.h | 1 + 4 files changed, 60 insertions(+), 3 deletions(-) diff --git a/drivers/mtd/nand/gpmi-nand/bch-regs.h b/drivers/mtd/nand/gpmi-nand/bch-regs.h index 588f537..a30502f 100644 --- a/drivers/mtd/nand/gpmi-nand/bch-regs.h +++ b/drivers/mtd/nand/gpmi-nand/bch-regs.h @@ -30,7 +30,9 @@ #define BM_BCH_CTRL_COMPLETE_IRQ (1 << 0) #define HW_BCH_STATUS0 0x00000010 +#define BM_BCH_STATUS0_ALLONES_MASK (1 << 4) #define HW_BCH_MODE 0x00000020 +#define BM_BCH_MODE_ERASE_THRESHOLD_MASK 0xff #define HW_BCH_ENCODEPTR 0x00000030 #define HW_BCH_DATAPTR 0x00000040 #define HW_BCH_METAPTR 0x00000050 diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-lib.c b/drivers/mtd/nand/gpmi-nand/gpmi-lib.c index aaced29..4551a38 100644 --- a/drivers/mtd/nand/gpmi-nand/gpmi-lib.c +++ b/drivers/mtd/nand/gpmi-nand/gpmi-lib.c @@ -286,6 +286,13 @@ int bch_set_geometry(struct gpmi_nand_data *this) | BF_BCH_FLASH0LAYOUT1_DATAN_SIZE(block_size, this), r->bch_regs + HW_BCH_FLASH0LAYOUT1); + /* + * Set the tolerance for bitflips when reading erased blocks + * equal to the ecc_strength. + */ + writel(bch_geo->ecc_strength & BM_BCH_MODE_ERASE_THRESHOLD_MASK, + r->bch_regs + HW_BCH_MODE); + /* Set *all* chip selects to use layout 0. */ writel(0, r->bch_regs + HW_BCH_LAYOUTSELECT); @@ -1094,6 +1101,16 @@ int gpmi_is_ready(struct gpmi_nand_data *this, unsigned chip) return reg & mask; } +/* Returns 1 if the last transaction consisted only out of ones. */ +int gpmi_allones(struct gpmi_nand_data *this) +{ + struct resources *r = &this->resources; + uint32_t reg = readl(r->gpmi_regs + HW_BCH_STATUS0); + if (reg & BM_BCH_STATUS0_ALLONES_MASK) + return 1; + return 0; +} + static inline void set_dma_type(struct gpmi_nand_data *this, enum dma_ops_type type) { diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c index dabbc14..82eac9b 100644 --- a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c +++ b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c @@ -1012,6 +1012,30 @@ static void block_mark_swapping(struct gpmi_nand_data *this, p[1] = (p[1] & mask) | (from_oob >> (8 - bit)); } +/* + * Count the number of 0 bits in a supposed to be + * erased region and correct them. Return the number + * of bitflips or zero when the region was correct. + */ +static unsigned int erased_sector_bitflips(unsigned char *data, + unsigned int chunk, + struct bch_geometry *geo) +{ + unsigned int flip_bits = 0; + int i; + int base = geo->ecc_chunk_size * chunk; + + /* Count bitflips */ + for (i = 0; i < geo->ecc_chunk_size; i++) + flip_bits += hweight8(~data[base + i]); + + /* Correct bitflips by 0xFF'ing this chunk. */ + if (flip_bits) + memset(&data[base], 0xFF, geo->ecc_chunk_size); + + return flip_bits; +} + static int gpmi_ecc_read_page(struct mtd_info *mtd, struct nand_chip *chip, uint8_t *buf, int oob_required, int page) { @@ -1023,6 +1047,7 @@ static int gpmi_ecc_read_page(struct mtd_info *mtd, struct nand_chip *chip, dma_addr_t auxiliary_phys; unsigned int i; unsigned char *status; + unsigned int flips; unsigned int max_bitflips = 0; int ret; @@ -1057,15 +1082,27 @@ static int gpmi_ecc_read_page(struct mtd_info *mtd, struct nand_chip *chip, status = auxiliary_virt + nfc_geo->auxiliary_status_offset; for (i = 0; i < nfc_geo->ecc_chunk_count; i++, status++) { - if ((*status == STATUS_GOOD) || (*status == STATUS_ERASED)) + if (*status == STATUS_GOOD) continue; if (*status == STATUS_UNCORRECTABLE) { mtd->ecc_stats.failed++; continue; } - mtd->ecc_stats.corrected += *status; - max_bitflips = max_t(unsigned int, max_bitflips, *status); + + if (*status == STATUS_ERASED) + if (gpmi_allones(this)) + continue; + else + /* Erased block with bitflips. */ + flips = erased_sector_bitflips(payload_virt, i, + nfc_geo); + else + /* BCH block corrected some errors for us. */ + flips = *status; + + mtd->ecc_stats.corrected += flips; + max_bitflips = max_t(unsigned int, max_bitflips, flips); } if (oob_required) { diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-nand.h b/drivers/mtd/nand/gpmi-nand/gpmi-nand.h index a7685e3..4ddd6af 100644 --- a/drivers/mtd/nand/gpmi-nand/gpmi-nand.h +++ b/drivers/mtd/nand/gpmi-nand/gpmi-nand.h @@ -268,6 +268,7 @@ extern void gpmi_clear_bch(struct gpmi_nand_data *); extern void gpmi_dump_info(struct gpmi_nand_data *); extern int bch_set_geometry(struct gpmi_nand_data *); extern int gpmi_is_ready(struct gpmi_nand_data *, unsigned chip); +extern int gpmi_allones(struct gpmi_nand_data *); extern int gpmi_send_command(struct gpmi_nand_data *); extern void gpmi_begin(struct gpmi_nand_data *); extern void gpmi_end(struct gpmi_nand_data *); -- 1.7.10.4