Re: [PATCH v4 02/11] mtd: cfi_cmdset_0002: Remove chip_ready() from do_write_buffer()

[Boris Brezillon <bbrezillon@kernel.org>]

On Tue,  5 Feb 2019 02:35:41 +0900
Tokunori Ikegami <ikegami_to@yahoo.co.jp> wrote:

> It is enough to use chip_good() only so chip_ready() is not necessary.
> Since chip_good() is doing the same check chip_ready() is doing plus an extra
> check to make sure we end up with the data we wrote.
> 
> For this change the order to check timeout also will be changed at same time.
> The order is not a hard requirement, it's just better to avoid the case where
> the data update happens just after the timeout has expired.
> 
> Signed-off-by: Tokunori Ikegami <ikegami_to@yahoo.co.jp>

This patch actually fixes a bug (as reported in the other thread), so
please add Fixes and Cc-stable tags and explain why it might cause
an infinite loop in the commit message.

> Cc: Fabio Bettoni <fbettoni@gmail.com>
> Co: Hauke Mehrtens <hauke@hauke-m.de>
> Co: Koen Vandeputte <koen.vandeputte@ncentric.com>
> Cc: Chris Packham <chris.packham@alliedtelesis.co.nz>
> Cc: Joakim Tjernlund <Joakim.Tjernlund@infinera.com>
> Cc: Boris Brezillon <boris.brezillon@free-electrons.com>
> Cc: linux-mtd@lists.infradead.org
> ---
> Changes since v3:
> - Update the commit message for the comment.
> - Change the email address of Tokunori Ikegami to ikegami_to@yahoo.co.jp.
> 
> Changes since v2:
> - None.
> 
> Changes since v1:
> - None.
> 
>  drivers/mtd/chips/cfi_cmdset_0002.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mtd/chips/cfi_cmdset_0002.c b/drivers/mtd/chips/cfi_cmdset_0002.c
> index 91a491b..ca9d5fa 100755
> --- a/drivers/mtd/chips/cfi_cmdset_0002.c
> +++ b/drivers/mtd/chips/cfi_cmdset_0002.c
> @@ -1878,14 +1878,14 @@ static int __xipram do_write_buffer(struct map_info *map, struct flchip *chip,
>  			continue;
>  		}
>  
> -		if (time_after(jiffies, timeo) && !chip_ready(map, adr))
> -			break;
> -
>  		if (chip_good(map, adr, datum)) {
>  			xip_enable(map, chip, adr);
>  			goto op_done;
>  		}
>  
> +		if (time_after(jiffies, timeo))
> +			break;
> +
>  		/* Latency issues. Drop the lock, wait a while and retry */
>  		UDELAY(map, chip, adr, 1);
>  	}


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