[PATCH v2] mtd: gpmi: Deal with bitflips in erased regions regions
Elie De Brauwer
eliedebrauwer at gmail.com
Sun Dec 15 13:44:21 EST 2013
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 <eliedebrauwer at gmail.com>
Acked-by: Peter Korsgaard <peter at korsgaard.com>
---
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
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