linux-kernel - Re: [PATCH] mmc: core: need retune if error value is -EIO

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Date:	Thu, 18 Aug 2016 16:10:37 +0800
From:	Shawn Lin <shawn.lin@...k-chips.com>
To:	Adrian Hunter <adrian.hunter@...el.com>,
	Ulf Hansson <ulf.hansson@...aro.org>
Cc:	shawn.lin@...k-chips.com, Jaehoon Chung <jh80.chung@...sung.com>,
	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-rockchip@...ts.infradead.org
Subject: Re: [PATCH] mmc: core: need retune if error value is -EIO

On 2016/8/18 15:19, Adrian Hunter wrote:
> On 04/08/16 11:30, Shawn Lin wrote:
>> We need to do retune if receiving -EIO, otherwise we
>> could see debug dump like:
>>
>> [ 89.057226] bcmsdh_sdmmc: Failed to Read byte F1:@0x1001f=ff, Err: -5
>> [ 89.058811] bcmsdh_sdmmc: Failed to Read byte F1:@0x1001f=ff, Err: -5
>> [ 89.059415] bcmsdh_sdmmc: Failed to Read byte F1:@0x1000e=ff, Err: -84
>> [ 89.254248] dwmmc_rockchip fe310000.dwmmc: Successfully tuned phase to 199
>> [ 89.273912] dhd_set_suspend: Remove extra suspend setting
>> [ 89.274478] dhd_enable_packet_filter: enter, value = 0
>> 64 bytes from 112.90.83.112: icmp_seq=24 ttl=53 time=1321 ms
>> 64 bytes from 112.90.83.112: icmp_seq=25 ttl=53 time=319 ms
>> 64 bytes from 112.90.83.112: icmp_seq=26 ttl=53 time=69.8 ms
>> 64 bytes from 112.90.83.112: icmp_seq=27 ttl=53 time=37.5 ms
>> ...
>>
>> In this case we see dw_mmc finally enter retune process, but
>> if this patch is applied, we could save more time to make it
>> work. Also many host drivers will generate -EIO, so this patch
>> can also prevent them from failing to enter retune process.
>
> The current logic is re-tune on CRC errors.  -EIO isn't informative
> and drivers can use it for cases that clearly are not related to tuning.
>

It actually relates to tuning. If failing to sample data or cmd-resp,
the controller generate timeout interrupt in principle rather than
explicit CRC ones. So it makes sense for them to return -EIO instead of
-EILSEQ as it's hard for the driver to understand what was happening,
crc? device is broken? ...

> A driver can call mmc_retune_needed() itself in other cases.

It's no so clear to this retune design as if the driver already knows
it's a CRC, it will generate -EILSEQ and let core do tuning again, so
it means they don't need to call mmc_return_needed in their drivers.
Unless let drivers return CRC in any cases of CRC or timeout, but that
may make core do tuning more frequently even if not relating to tuning
which seems a little painful.

So it looks quite vague to me.:)

>
>>
>> Signed-off-by: Shawn Lin <shawn.lin@...k-chips.com>
>> ---
>>
>>  drivers/mmc/core/core.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
>> index e55cde6..18d0af5 100644
>> --- a/drivers/mmc/core/core.c
>> +++ b/drivers/mmc/core/core.c
>> @@ -133,7 +133,8 @@ void mmc_request_done(struct mmc_host *host, struct mmc_request *mrq)
>>  	/* Flag re-tuning needed on CRC errors */
>>  	if ((cmd->opcode != MMC_SEND_TUNING_BLOCK &&
>>  	    cmd->opcode != MMC_SEND_TUNING_BLOCK_HS200) &&
>> -	    (err == -EILSEQ || (mrq->sbc && mrq->sbc->error == -EILSEQ) ||
>> +	    (err == -EILSEQ || err == -EIO ||
>> +	    (mrq->sbc && mrq->sbc->error == -EILSEQ) ||
>>  	    (mrq->data && mrq->data->error == -EILSEQ) ||
>>  	    (mrq->stop && mrq->stop->error == -EILSEQ)))
>>  		mmc_retune_needed(host);
>>
>
>
>
>


-- 
Best Regards
Shawn Lin