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SubjectRe: [PATCH 2/2] Use bit-wise majority to recover the contents of ONFI parameter
Hi Jane,

Same comments as before, please: get the right maintainers, add a
commit log, rebase and fix the title prefix.

Have you ever needed/tried this algorithm before?

On Thu, 26 Apr 2018 17:19:56 -0700, Jane Wan
<Jane.Wan@nokia.com> wrote:

> Signed-off-by: Jane Wan <Jane.Wan@nokia.com>
> ---
> drivers/mtd/nand/nand_base.c | 35 +++++++++++++++++++++++++++++++----
> 1 file changed, 31 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
> index c2e1232..161b523 100644
> --- a/drivers/mtd/nand/nand_base.c
> +++ b/drivers/mtd/nand/nand_base.c
> @@ -3153,8 +3153,10 @@ static int nand_flash_detect_onfi(struct mtd_info *mtd, struct nand_chip *chip,
> int *busw)
> {
> struct nand_onfi_params *p = &chip->onfi_params;
> - int i, j;
> - int val;
> + int i, j, k, len, val;
> + uint8_t copy[3][256], v8;

Please use u8 instead of uint8_t (./scripts/checkpatch.pl --strict will
give you the list of styling issues to fix.

I don't think you should allocate that much space on the stack, please
use dynamic allocation.

> +
> + len = (sizeof(*p) > 256) ? 256 : sizeof(*p);

This is a maximum derivation, there are helpers for that.

I am not sure this is relevant, won't you read only 256 bytes anyway?

>
> /* Try ONFI for unknown chip or LP */
> chip->cmdfunc(mtd, NAND_CMD_READID, 0x20, -1);
> @@ -3170,11 +3172,36 @@ static int nand_flash_detect_onfi(struct mtd_info *mtd, struct nand_chip *chip,
> le16_to_cpu(p->crc)) {
> break;
> }

Space.

> + pr_err("CRC of parameter page %d is not valid\n", i);
> + for (j = 0; j < len; j++)
> + copy[i][j] = ((uint8_t *)p)[j];

'copy' is maybe not a meaningful name.

> }
>
> if (i == 3) {
> - pr_err("Could not find valid ONFI parameter page; aborting\n");
> - return 0;
> + pr_err("Could not find valid ONFI parameter page\n");
> + pr_info("Recover ONFI parameters with bit-wise majority\n");
> + for (j = 0; j < len; j++) {
> + if (copy[0][j] == copy[1][j] ||
> + copy[0][j] == copy[2][j]) {
> + ((uint8_t *)p)[j] = copy[0][j];
> + } else if (copy[1][j] == copy[2][j]) {
> + ((uint8_t *)p)[j] = copy[1][j];
> + } else {
> + ((uint8_t *)p)[j] = 0;
> + for (k = 0; k < 8; k++) {
> + v8 = (copy[0][j] >> k) & 0x1;

v8 could be declared in the else statement of in the for loop.
The name could also be changed.

> + v8 += (copy[1][j] >> k) & 0x1;
> + v8 += (copy[2][j] >> k) & 0x1;
> + if (v8 > 1)
> + ((uint8_t *)p)[j] |= (1 << k);

Please use the BIT() macro.

> + }
> + }
> + }

Space.

> + if (onfi_crc16(ONFI_CRC_BASE, (uint8_t *)p, 254) !=
> + le16_to_cpu(p->crc)) {
> + pr_err("ONFI parameter recovery failed, aborting\n");
> + return 0;
> + }
> }
>
> /* Check version */

Thanks,
Miquèl

--
Miquel Raynal, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com

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