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Subject[PATCH v4 2/2] mtd: rawnand: use bit-wise majority to recover the contents of ONFI parameter
Date
Per ONFI specification (Rev. 4.0), if all parameter pages have invalid
CRC values, the bit-wise majority may be used to recover the contents of
the parameter pages from the parameter page copies present.

Signed-off-by: Jane Wan <Jane.Wan@nokia.com>
---
drivers/mtd/nand/raw/nand_base.c | 49 ++++++++++++++++++++++++++++++++++----
1 file changed, 44 insertions(+), 5 deletions(-)

diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
index 72f3a89..dfc341c 100644
--- a/drivers/mtd/nand/raw/nand_base.c
+++ b/drivers/mtd/nand/raw/nand_base.c
@@ -5086,6 +5086,38 @@ static int nand_flash_detect_ext_param_page(struct nand_chip *chip,
return ret;
}

+#define GET_BIT(bit, val) (((val) >> (bit)) & 0x01)
+
+/*
+ * Recover NAND parameter page with bit-wise majority
+ */
+static int onfi_recover_param(struct nand_onfi_params *p, int pages)
+{
+ int i, j, k;
+ u8 v, m;
+ u8 *buf;
+
+ buf = (u8 *)p;
+ for (i = 0; i < sizeof(*p); i++) {
+ v = 0;
+ for (j = 0; j < 8; j++) {
+ m = 0;
+ for (k = 0; k < pages; k++)
+ m += GET_BIT(j, buf[k*sizeof(*p) + i]);
+ if (m > pages/2)
+ v |= BIT(j);
+ }
+ ((u8 *)p)[i] = v;
+ }
+
+ if (onfi_crc16(ONFI_CRC_BASE, (u8 *)p, 254) ==
+ le16_to_cpu(p->crc)) {
+ return 1;
+ }
+
+ return 0;
+}
+
/*
* Check if the NAND chip is ONFI compliant, returns 1 if it is, 0 otherwise.
*/
@@ -5102,7 +5134,7 @@ static int nand_flash_detect_onfi(struct nand_chip *chip)
return 0;

/* ONFI chip: allocate a buffer to hold its parameter page */
- p = kzalloc(sizeof(*p), GFP_KERNEL);
+ p = kzalloc((sizeof(*p) * 3), GFP_KERNEL);
if (!p)
return -ENOMEM;

@@ -5113,21 +5145,28 @@ static int nand_flash_detect_onfi(struct nand_chip *chip)
}

for (i = 0; i < 3; i++) {
- ret = nand_read_data_op(chip, p, sizeof(*p), true);
+ ret = nand_read_data_op(chip, &p[i], sizeof(*p), true);
if (ret) {
ret = 0;
goto free_onfi_param_page;
}

- if (onfi_crc16(ONFI_CRC_BASE, (uint8_t *)p, 254) ==
+ if (onfi_crc16(ONFI_CRC_BASE, (u8 *)&p[i], 254) ==
le16_to_cpu(p->crc)) {
+ if (i)
+ memcpy(p, &p[i], sizeof(*p));
break;
}
}

if (i == 3) {
- pr_err("Could not find valid ONFI parameter page; aborting\n");
- goto free_onfi_param_page;
+ pr_err("Could not find valid ONFI parameter page\n");
+ pr_info("Recover ONFI params with bit-wise majority\n");
+ ret = onfi_recover_param(p, 3);
+ if (ret == 0) {
+ pr_err("ONFI parameter recovery failed, aborting\n");
+ goto free_onfi_param_page;
+ }
}

/* Check version */
--
1.7.9.5
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