RE: [PATCH v3] cfi: fix deadloop in cfi_cmdset_0002.c do_write_buffer

["Tokunori Ikegami" <ikegami.t@xxxxxxxxx>]

> -----Original Message-----
> From: linux-mtd [mailto:linux-mtd-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf
> Of Liu Jian
> Sent: Tuesday, February 26, 2019 11:01 PM
> To: dwmw2@xxxxxxxxxxxxx; computersforpeace@xxxxxxxxx;
> bbrezillon@xxxxxxxxxx; marek.vasut@xxxxxxxxx; richard@xxxxxx;
> joakim.tjernlund@xxxxxxxxxxxx; ikegami@xxxxxxxxxxxxxxxxxxxx;
> keescook@xxxxxxxxxxxx; vigneshr@xxxxxx
> Cc: linux-mtd@xxxxxxxxxxxxxxxxxxx; liujian56@xxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx
> Subject: [PATCH v3] cfi: fix deadloop in cfi_cmdset_0002.c do_write_buffer
> 
> In function do_write_buffer(), in the for loop, there is a case
> chip_ready() returns 1 while chip_good() returns 0, so it never
> break the loop.
> To fix this, chip_good() is enough and it should timeout if it stay
> bad for a while.
> 
> Fixes: dfeae1073583("mtd: cfi_cmdset_0002: Change write buffer to check
> correct value")
> Signed-off-by: Yi Huaijie <yihuaijie@xxxxxxxxxx>
> Signed-off-by: Liu Jian <liujian56@xxxxxxxxxx>
> Reviewed-by: Tokunori Ikegami <ikegami_to@xxxxxxxxxxx>
> ---
> v2->v3:
> Follow Vignesh's advice:
> add one more check for check_good() even when time_after() returns true.
> 
>  drivers/mtd/chips/cfi_cmdset_0002.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/chips/cfi_cmdset_0002.c
> b/drivers/mtd/chips/cfi_cmdset_0002.c
> index 72428b6..3da2376 100644
> --- a/drivers/mtd/chips/cfi_cmdset_0002.c
> +++ b/drivers/mtd/chips/cfi_cmdset_0002.c
> @@ -1876,7 +1876,7 @@ static int __xipram do_write_buffer(struct map_info
> *map, struct flchip *chip,
>  			continue;
>  		}
> 
> -		if (time_after(jiffies, timeo) && !chip_ready(map, adr))
> +		if (time_after(jiffies, timeo) && !chip_good(map, adr,
> datum))

  Just another idea to understand easily.

    unsigned long now = jiffies;

    if (chip_good(map, adr, datum)) {
        xip_enable(map, chip, adr);
        goto op_done;
    }

    if (time_after(now, timeo) {
        break;
    }

Regards,
Ikegami

>  			break;
> 
>  		if (chip_good(map, adr, datum)) {
> --
> 2.7.4
> 
> 
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