Re: mtd: cfi: Fixed endless loop problem in CFI when value was written but corrupted.

[Chris Packham <Chris.Packham@alliedtelesis.co.nz>]

Hi All,

On 8/02/19 12:58 PM, Przemyslaw Sobon wrote:
> Fixes: dfeae1073583(mtd: cfi_cmdset_0002: Change write buffer to
>         check correct value)
> 
> There was an endless loop in CFI Flash driver when a value was written
> incorrectly. In such case chip_ready returns true but chip_good returns
> false and we never get out of the loop.
> 
> The solution was to break the loop in 2 cases, either device is ready or
> device is not ready and timeout elapsed. The correctness of the write is
> checked after the loop ended. That way we ensure the loop always ends.
> 
> Signed-off-by: Przemyslaw Sobon <psobon@amazon.com>

Mark (cc'd) has done some testing here, and assuming he's happy with the 
forgery.

Tested-by: Mark Tomlinson <Mark.Tomlinson@alliedtelesis.co.nz>

> ---
>   drivers/mtd/chips/cfi_cmdset_0002.c | 11 +++++++----
>   1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/mtd/chips/cfi_cmdset_0002.c b/drivers/mtd/chips/cfi_cmdset_0002.c
> index 72428b6bfc47..6cc31d2057e9 100644
> --- a/drivers/mtd/chips/cfi_cmdset_0002.c
> +++ b/drivers/mtd/chips/cfi_cmdset_0002.c
> @@ -1879,15 +1879,18 @@ static int __xipram do_write_buffer(struct map_info *map, struct flchip *chip,
>   		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 (chip_ready(map, adr))
> +			break;
>   
>   		/* Latency issues. Drop the lock, wait a while and retry */
>   		UDELAY(map, chip, adr, 1);
>   	}
>   
> +	if (chip_good(map, adr, datum)) {
> +		xip_enable(map, chip, adr);
> +		goto op_done;
> +	}
> +
>   	/*
>   	 * Recovery from write-buffer programming failures requires
>   	 * the write-to-buffer-reset sequence.  Since the last part
> 


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