linux-kernel - Re: [PATCH 4.4 25/31] mmc: dw_mmc: Wait for data transfer after response errors.

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Date:   Thu, 26 Aug 2021 08:31:28 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     Nobuhiro Iwamatsu <iwamatsu@...auri.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        stable@...r.kernel.org, Doug Anderson <dianders@...omium.org>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Alim Akhtar <alim.akhtar@...il.com>,
        Jaehoon Chung <jh80.chung@...sung.com>,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH 4.4 25/31] mmc: dw_mmc: Wait for data transfer after
 response errors.

On Thu, Aug 26, 2021 at 08:59:53PM +0900, Nobuhiro Iwamatsu wrote:
>Hi,
>
>
>2021年8月25日(水) 2:39 Sasha Levin <sashal@...nel.org>:
>>
>> From: Doug Anderson <dianders@...omium.org>
>>
>> [ Upstream commit 46d179525a1f6d16957dcb4624517bc04142b3e7 ]
>>
>> According to the DesignWare state machine description, after we get a
>> "response error" or "response CRC error" we move into data transfer
>> mode. That means that we don't necessarily need to special case
>> trying to deal with the failure right away. We can wait until we are
>> notified that the data transfer is complete (with or without errors)
>> and then we can deal with the failure.
>>
>> It may sound strange to defer dealing with a command that we know will
>> fail anyway, but this appears to fix a bug. During tuning (CMD19) on
>> a specific card on an rk3288-based system, we found that we could get
>> a "response CRC error". Sending the stop command after the "response
>> CRC error" would then throw the system into a confused state causing
>> all future tuning phases to report failure.
>>
>> When in the confused state, the controller would show these (hex codes
>> are interrupt status register):
>>  CMD ERR: 0x00000046 (cmd=19)
>>  CMD ERR: 0x0000004e (cmd=12)
>>  DATA ERR: 0x00000208
>>  DATA ERR: 0x0000020c
>>  CMD ERR: 0x00000104 (cmd=19)
>>  CMD ERR: 0x00000104 (cmd=12)
>>  DATA ERR: 0x00000208
>>  DATA ERR: 0x0000020c
>>  ...
>>  ...
>>
>> It is inherently difficult to deal with the complexity of trying to
>> correctly send a stop command while a data transfer is taking place
>> since you need to deal with different corner cases caused by the fact
>> that the data transfer could complete (with errors or without errors)
>> during various places in sending the stop command (dw_mci_stop_dma,
>> send_stop_abort, etc)
>>
>> Instead of adding a bunch of extra complexity to deal with this, it
>> seems much simpler to just use the more straightforward (and less
>> error-prone) path of letting the data transfer finish. There
>> shouldn't be any huge benefit to sending the stop command slightly
>> earlier, anyway.
>>
>> Signed-off-by: Doug Anderson <dianders@...omium.org>
>> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>
>> Cc: Alim Akhtar <alim.akhtar@...il.com>
>> Signed-off-by: Jaehoon Chung <jh80.chung@...sung.com>
>> Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
>> Signed-off-by: Sasha Levin <sashal@...nel.org>
>
>This commit also requires the following modifications:
>  ba2d139b02ba68: mmc: dw_mmc: Fix occasional hang after tuning on eMMC
>
>Please apply this commit too.

Will do, thanks!

-- 
Thanks,
Sasha