[RFC] mtd: nand: Add a STATUS CMD after write verification

[Bastian Hecht]

2012/4/18 Bastian Hecht <hechtb at googlemail.com>:
> When using CONFIG_MTD_NAND_VERIFY_WRITE=y an extra read command is sent
> to the NAND chip after writing a page. We need an extra status command
> to avoid hick-ups that lead to page write failures.
> ---
>
> Hello all,
>
> I'm experiencing problems with my current setup and
> CONFIG_MTD_NAND_VERIFY_WRITE=y. Usually the command sequence is like
> 0x70            Status read
> 0x80 0x10       Page prog
> 0x70
> 0x80 0x10       Page prog
> 0x70
> ...
>
> When activating write verification there is a read command before the
> page prog.

I've written this unclearly. I mean if we issue multiple page writes,
the page writes are not preceeded by a status read, but by a page read
command from the last verification.

> 0x80 0x10
> 0x70
> 0x0             read
> 0x80 0x10
> 0x70
> ...
> This makes my chip write garbage, while the patch fixes it.
> Now I wonder if this problem is caused by my NAND chip only, or if this
> is a general problem that should be adressed.
> ---
>  drivers/mtd/nand/nand_base.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
> index 8a393f9..62d6691 100644
> --- a/drivers/mtd/nand/nand_base.c
> +++ b/drivers/mtd/nand/nand_base.c
> @@ -2101,6 +2101,8 @@ static int nand_write_page(struct mtd_info *mtd, struct nand_chip *chip,
>
>        if (chip->verify_buf(mtd, buf, mtd->writesize))
>                return -EIO;
> +
> +       chip->cmdfunc(mtd, NAND_CMD_STATUS, -1, -1);
>  #endif
>        return 0;
>  }
> --
> 1.7.5.4
>