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Subject[PATCH v2 2/2] mtd: rawnand: fsl_ifc: 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 | 36 ++++++++++++++++++++++++++++++------
1 file changed, 30 insertions(+), 6 deletions(-)

diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
index 72f3a89..464c4fb 100644
--- a/drivers/mtd/nand/raw/nand_base.c
+++ b/drivers/mtd/nand/raw/nand_base.c
@@ -5086,6 +5086,8 @@ static int nand_flash_detect_ext_param_page(struct nand_chip *chip,
return ret;
}

+#define GET_BIT(bit, val) (((val) >> (bit)) & 0x01)
+
/*
* Check if the NAND chip is ONFI compliant, returns 1 if it is, 0 otherwise.
*/
@@ -5094,7 +5096,8 @@ static int nand_flash_detect_onfi(struct nand_chip *chip)
struct mtd_info *mtd = nand_to_mtd(chip);
struct nand_onfi_params *p;
char id[4];
- int i, ret, val;
+ int i, ret, val, pagesize;
+ u8 *buf;

/* Try ONFI for unknown chip or LP */
ret = nand_readid_op(chip, 0x20, id, sizeof(id));
@@ -5102,8 +5105,9 @@ 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);
- if (!p)
+ pagesize = sizeof(*p);
+ buf = kzalloc((pagesize * 3), GFP_KERNEL);
+ if (!buf)
return -ENOMEM;

ret = nand_read_param_page_op(chip, 0, NULL, 0);
@@ -5113,7 +5117,8 @@ 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);
+ p = (struct nand_onfi_params *)&buf[i*pagesize];
+ ret = nand_read_data_op(chip, p, pagesize, true);
if (ret) {
ret = 0;
goto free_onfi_param_page;
@@ -5126,8 +5131,27 @@ static int nand_flash_detect_onfi(struct nand_chip *chip)
}

if (i == 3) {
- pr_err("Could not find valid ONFI parameter page; aborting\n");
- goto free_onfi_param_page;
+ int j, k, l;
+ u8 v, m;
+
+ pr_err("Could not find valid ONFI parameter page\n");
+ pr_info("Recover ONFI params with bit-wise majority\n");
+ for (j = 0; j < pagesize; j++) {
+ v = 0;
+ for (k = 0; k < 8; k++) {
+ m = 0;
+ for (l = 0; l < 3; l++)
+ m += GET_BIT(k, buf[l*pagesize + j]);
+ if (m > 1)
+ v |= BIT(k);
+ }
+ ((u8 *)p)[j] = v;
+ }
+ if (onfi_crc16(ONFI_CRC_BASE, (uint8_t *)p, 254) !=
+ le16_to_cpu(p->crc)) {
+ pr_err("ONFI parameter recovery failed, aborting\n");
+ goto free_onfi_param_page;
+ }
}

/* Check version */
--
1.7.9.5
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