[PATCH v7] mtd: rawnand: use bit-wise majority to recover the contents of ONFI parameter

Wan, Jane (Nokia - US/Sunnyvale)
2018-05-13T04:30:27Z

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>
---
v7: change debug print messages
v6: support the cases that srcbufs are not contiguous
v5: make the bit-wise majority functon generic
v4: move the bit-wise majority code in a separate function
v3: fix warning message detected by kbuild test robot
v2: rebase the changes on top of v4.17-rc1

drivers/mtd/nand/raw/nand_base.c | 50 ++++++++++++++++++++++++++++++++++----
1 file changed, 45 insertions(+), 5 deletions(-)

diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
index 72f3a89..b43b784 100644
--- a/drivers/mtd/nand/raw/nand_base.c
+++ b/drivers/mtd/nand/raw/nand_base.c
@@ -5087,6 +5087,35 @@ static int nand_flash_detect_ext_param_page(struct nand_chip *chip,
}

/*
+ * Recover data with bit-wise majority
+ */
+static void nand_bit_wise_majority(const void **srcbufs,
+ unsigned int nsrcbufs,
+ void *dstbuf,
+ unsigned int bufsize)
+{
+ int i, j, k;
+
+ for (i = 0; i < bufsize; i++) {
+ u8 cnt, val;
+
+ val = 0;
+ for (j = 0; j < 8; j++) {
+ cnt = 0;
+ for (k = 0; k < nsrcbufs; k++) {
+ const u8 *srcbuf = srcbufs[k];
+
+ if (srcbuf[i] & BIT(j))
+ cnt++;
+ }
+ if (cnt > nsrcbufs / 2)
+ val |= BIT(j);
+ }
+ ((u8 *)dstbuf)[i] = val;
+ }
+}
+
+/*
* Check if the NAND chip is ONFI compliant, returns 1 if it is, 0 otherwise.
*/
static int nand_flash_detect_onfi(struct nand_chip *chip)
@@ -5102,7 +5131,7 @@ 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 +5142,32 @@ 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;
+ const void *srcbufs[3] = {p, p + 1, p + 2};
+
+ pr_warn("Could not find a valid ONFI parameter page, trying bit-wise majority to recover it\n");
+ nand_bit_wise_majority(srcbufs, ARRAY_SIZE(srcbufs), p,
+ sizeof(*p));
+
+ if (onfi_crc16(ONFI_CRC_BASE, (u8 *)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