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Date: Mon, 14 Jan 2019 09:45:27 +0100
From: Boris Brezillon <bbrezillon@kernel.org>
To: Przemyslaw Sobon <psobon@amazon.com>
Cc: David Woodhouse <dwmw2@infradead.org>, Brian Norris
 <computersforpeace@gmail.com>, "Marek Vasut" <marek.vasut@gmail.com>,
 Richard Weinberger <richard@nod.at>, <linux-mtd@lists.infradead.org>
Subject: Re: [PATCH] Fixed endless loop problem in CFI when value was
 written but corrupted.
Message-ID: <20190114094527.49093d25@bbrezillon>
In-Reply-To: <20190108165125.GA95492@dev-dsk-psobon-2c-1dd9f399.us-west-2.amazon.com>
References: <20190108165125.GA95492@dev-dsk-psobon-2c-1dd9f399.us-west-2.amazon.com>
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Hi Przemyslaw,

Subject prefix should be "mtd: cfi: ".

On Tue, 8 Jan 2019 16:51:25 +0000
Przemyslaw Sobon <psobon@amazon.com> wrote:

> 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>
> ---
>  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

Can you look at this series [1], it might fix your problem. I didn't
apply these patches because I was not happy with the explanation given
in the commit message and Ikegami never sent a v4 to address that :-/.

Regards,

Boris

[1]http://patchwork.ozlabs.org/project/linux-mtd/list/?series=72607