linux-kernel - Re: [PATCH 7/8] spi: spi-s3c64xx: Increase transfer timeout

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Date:   Wed, 19 Aug 2020 15:39:56 +0200
From:   Lukasz Stelmach <l.stelmach@...sung.com>
To:     Krzysztof Kozlowski <krzk@...nel.org>
Cc:     Kukjin Kim <kgene@...nel.org>, Andi Shyti <andi@...zian.org>,
        Mark Brown <broonie@...nel.org>, linux-spi@...r.kernel.org,
        linux-samsung-soc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        m.szyprowski@...sung.com, b.zolnierkie@...sung.com
Subject: Re: [PATCH 7/8] spi: spi-s3c64xx: Increase transfer timeout

It was <2020-08-19 śro 14:49>, when Krzysztof Kozlowski wrote:
> On Wed, Aug 19, 2020 at 02:32:07PM +0200, Łukasz Stelmach wrote:
>> Signed-off-by: Łukasz Stelmach <l.stelmach@...sung.com>
>
> Why? Everything works fine and suddenly minimum timeout is 100 ms?

Actually I am not 100% sure the max() call is required, maybe +30 is
enough. Definitely some minimum value is required because for small
tranfers (100s of bytes) ms is 0 after the first assignment.

>> ---
>>  drivers/spi/spi-s3c64xx.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>> 
>> diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
>> index 27d77600a820..27db1e0f6f32 100644
>> --- a/drivers/spi/spi-s3c64xx.c
>> +++ b/drivers/spi/spi-s3c64xx.c
>> @@ -464,7 +464,8 @@ static int s3c64xx_wait_for_dma(struct s3c64xx_spi_driver_data *sdd,
>>  
>>  	/* millisecs to xfer 'len' bytes @ 'cur_speed' */
>>  	ms = xfer->len * 8 * 1000 / sdd->cur_speed;
>> -	ms += 10; /* some tolerance */
>> +	ms = (ms * 10) + 30;    /* some tolerance */
>> +	ms = max(ms, 100);      /* minimum timeout */
>>  
>>  	val = msecs_to_jiffies(ms) + 10;
>>  	val = wait_for_completion_timeout(&sdd->xfer_completion, val);
>> -- 
>> 2.26.2
>> 
>
>

-- 
Łukasz Stelmach
Samsung R&D Institute Poland
Samsung Electronics

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