Hello,

Can you please provide your comments on this patch.

Thanks,
Balamanikandan

On 29/06/21 12:46 pm, Balamanikandan Gunasundar wrote:
> The command shall be used to induce bit errors in the nand page
> manually. The code flips a bit in the specified offset without
> changing the ECC. This helps to see how the software handles the
> error.
> 
> The patch is ported from
> https://patchwork.ozlabs.org/project/uboot/patch/\
> 1325691123-19565-1-git-send-email-holger.bru...@keymile.com
> 
> The implementation is inspired from
> 'mtd-utils/nand-utils/nandflipbits.c'
> 
> Signed-off-by: Balamanikandan Gunasundar 
> <balamanikandan.gunasun...@microchip.com>
> ---
>   cmd/nand.c | 127 +++++++++++++++++++++++++++++++++++++++++++++++++++--
>   1 file changed, 124 insertions(+), 3 deletions(-)
> 
> diff --git a/cmd/nand.c b/cmd/nand.c
> index 5bda69e819..ea1b0f9434 100644
> --- a/cmd/nand.c
> +++ b/cmd/nand.c
> @@ -17,6 +17,10 @@
>    * and/or modified under the terms of the GNU General Public License as
>    * published by the Free Software Foundation; either version 2 of the
>    * License, or (at your option) any later version.
> + *
> + * The function nand_biterror() in this file is inspired from
> + * mtd-utils/nand-utils/nandflipbits.c which was released under GPLv2
> + * only
>    */
>   
>   #include <common.h>
> @@ -40,6 +44,116 @@ int find_dev_and_part(const char *id, struct mtd_device 
> **dev,
>                     u8 *part_num, struct part_info **part);
>   #endif
>   
> +#define MAX_NUM_PAGES 64
> +
> +static int nand_biterror(struct mtd_info *mtd, ulong off, int bit)
> +{
> +     int ret = 0;
> +     int page = 0;
> +     ulong  block_off;
> +     u_char *datbuf[MAX_NUM_PAGES]; /* Data and OOB */
> +     u_char data;
> +     int pages_per_blk = mtd->erasesize / mtd->writesize;
> +     struct erase_info einfo;
> +
> +     if (pages_per_blk > MAX_NUM_PAGES) {
> +             printf("Too many pages in one erase block\n");
> +             return 1;
> +     }
> +
> +     if (bit < 0 || bit > 7) {
> +             printf("bit position 0 to 7 is allowed\n");
> +             return 1;
> +     }
> +
> +     /* Allocate memory */
> +     memset(datbuf, 0, sizeof(datbuf));
> +     for (page = 0; page < pages_per_blk ; page++) {
> +             datbuf[page] = malloc(mtd->writesize + mtd->oobsize);
> +             if (!datbuf[page]) {
> +                     printf("No memory for page buffer\n");
> +                     ret = -ENOMEM;
> +                     goto free_memory;
> +             }
> +     }
> +
> +     /* Align to erase block boundary */
> +     block_off = off & (~(mtd->erasesize - 1));
> +
> +     /* Read out memory as first step */
> +     for (page = 0; page < pages_per_blk ; page++) {
> +             struct mtd_oob_ops ops;
> +             loff_t addr = (loff_t)block_off;
> +
> +             memset(&ops, 0, sizeof(ops));
> +             ops.datbuf = datbuf[page];
> +             ops.oobbuf = datbuf[page] + mtd->writesize;
> +             ops.len = mtd->writesize;
> +             ops.ooblen = mtd->oobsize;
> +             ops.mode = MTD_OPS_RAW;
> +             ret = mtd_read_oob(mtd, addr, &ops);
> +             if (ret < 0) {
> +                     printf("Error (%d) reading page %08lx\n",
> +                            ret, block_off);
> +                     ret = 1;
> +                     goto free_memory;
> +             }
> +             block_off += mtd->writesize;
> +     }
> +
> +     /* Erase the block */
> +     memset(&einfo, 0, sizeof(einfo));
> +     einfo.mtd = mtd;
> +     /* Align to erase block boundary */
> +     einfo.addr = (loff_t)(off & (~(mtd->erasesize - 1)));
> +     einfo.len = mtd->erasesize;
> +     ret = mtd_erase(mtd, &einfo);
> +     if (ret < 0) {
> +             printf("Error (%d) nand_erase_nand page %08llx\n",
> +                    ret, einfo.addr);
> +             ret = 1;
> +             goto free_memory;
> +     }
> +
> +     /* Twist a bit in data part */
> +     block_off = off & (mtd->erasesize - 1);
> +     data = datbuf[block_off / mtd->writesize][block_off % mtd->writesize];
> +     data ^= (1 << bit);
> +     datbuf[block_off / mtd->writesize][block_off % mtd->writesize] = data;
> +
> +     printf("Flip data at 0x%lx with xor 0x%02x (bit=%d) to value=0x%02x\n",
> +            off, (1 << bit), bit, data);
> +
> +     /* Write back twisted data and unmodified OOB */
> +     /* Align to erase block boundary */
> +     block_off = off & (~(mtd->erasesize - 1));
> +     for (page = 0; page < pages_per_blk; page++) {
> +             struct mtd_oob_ops ops;
> +             loff_t addr = (loff_t)block_off;
> +
> +             memset(&ops, 0, sizeof(ops));
> +             ops.datbuf = datbuf[page];
> +             ops.oobbuf = datbuf[page] + mtd->writesize;
> +             ops.len = mtd->writesize;
> +             ops.ooblen = mtd->oobsize;
> +             ops.mode = MTD_OPS_RAW;
> +             ret = mtd_write_oob(mtd, addr, &ops);
> +             if (ret < 0) {
> +                     printf("Error (%d) write page %08lx\n", ret, block_off);
> +                     ret = 1;
> +                     goto free_memory;
> +             }
> +             block_off += mtd->writesize;
> +     }
> +
> +free_memory:
> +     for (page = 0; page < pages_per_blk ; page++) {
> +             if (datbuf[page])
> +                     free(datbuf[page]);
> +     }
> +     return ret;
> +}
> +
>   static int nand_dump(struct mtd_info *mtd, ulong off, int only_oob,
>                    int repeat)
>   {
> @@ -728,8 +842,15 @@ static int do_nand(cmd_tbl_t *cmdtp, int flag, int argc, 
> char * const argv[])
>       }
>   
>       if (strcmp(cmd, "biterr") == 0) {
> -             /* todo */
> -             return 1;
> +             int bit;
> +
> +             if (argc != 4)
> +                     goto usage;
> +
> +             off = (int)simple_strtoul(argv[2], NULL, 16);
> +             bit = (int)simple_strtoul(argv[3], NULL, 10);
> +             ret = nand_biterror(mtd, off, bit);
> +             return ret;
>       }
>   
>   #ifdef CONFIG_CMD_NAND_LOCK_UNLOCK
> @@ -820,7 +941,7 @@ static char nand_help_text[] =
>       "nand scrub [-y] off size | scrub.part partition | scrub.chip\n"
>       "    really clean NAND erasing bad blocks (UNSAFE)\n"
>       "nand markbad off [...] - mark bad block(s) at offset (UNSAFE)\n"
> -     "nand biterr off - make a bit error at offset (UNSAFE)"
> +     "nand biterr off bit - make a bit error at offset and bit position 
> (UNSAFE)"
>   #ifdef CONFIG_CMD_NAND_LOCK_UNLOCK
>       "\n"
>       "nand lock [tight] [status]\n"
> 

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