linux-kernel - Re: [PATCH] mmc: dw_mmc: Wait for data transfer after response errors

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Message-id: <56FC856F.1010909@samsung.com>
Date:	Thu, 31 Mar 2016 11:03:27 +0900
From:	Jaehoon Chung <jh80.chung@...sung.com>
To:	Enric Balletbo Serra <eballetbo@...il.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Doug Anderson <dianders@...omium.org>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Alim Akhtar <alim.akhtar@...il.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Alim Akhtar <alim.akhtar@...sung.com>,
	Sonny Rao <sonnyrao@...omium.org>,
	Andrew Bresticker <abrestic@...omium.org>,
	Heiko Stuebner <heiko@...ech.de>,
	Addy Ke <addy.ke@...k-chips.com>,
	Alexandru Stan <amstan@...omium.org>,
	Chris Zhong <zyw@...k-chips.com>,
	Caesar Wang <wxt@...k-chips.com>,
	Javier Martinez Canillas <javier@....samsung.com>
Subject: Re: [PATCH] mmc: dw_mmc: Wait for data transfer after response errors

On 03/31/2016 02:16 AM, Enric Balletbo Serra wrote:
> 2016-03-24 17:22 GMT+01:00 Russell King - ARM Linux <linux@....linux.org.uk>:
>> On Thu, Mar 24, 2016 at 09:06:45AM -0700, Doug Anderson wrote:
>>> Russell,
>> ...
>>> Presumably this is similar to what you saw: the host saw the CRC error
>>> but the card knew nothing about it.  Sending the stop command during
>>> this time confused the card.  Presumably the card was in transfer
>>> state during this time?
>>
>> If the card was in transfer state for a command which expects a stop
>> command, and that stop command was issued after the card entered
>> the transfer state, then I'd expect the card to handle it... though
>> there's always the firmware bug issue.
>>
>> If the card hadn't entered transfer state at the time the stop command
>> was issued.. I think that's more likely to hit card firmware issues.
>>
>> With the tuning commands, there's another case you can hit though:
>> the data transfer may have completed before you get around to sending
>> the stop command.
>>
>> That's why, for sdhci, I came to the conclusion that waiting for the
>> data transfer to complete or timeout was the best solution for SDHCI.
>>
> 
> In fact I only saw the problem with dw_mmc-exynos, on dw_mmc-rockchip
> it doesn't happen because it enables the DW_MCI_QUIRK_BROKEN_DTO
> behaviour. What does this is use a kernel timer to signal when DTO
> interrupt does NOT come. Note that if I disable this quirk I can also
> saw the problem on rockchip.

Did you see the problem with exynos? Could you share which exynos chip you use?
Then i can check this with all exynos.

> 
>> Maybe, if sending a STOP command does cause card firmware issues, then:
>>
>> 1) it provides evidence that trying to send a stop command on response
>>    CRC error is the wrong thing to do (it was talked about making SDHCI
>>    do this.)
>>
> 
> Seems the same here, so guess is the wrong thing to do.
> 
>> 2) it suggests that the solution I came up with for SDHCI is the better
>>    solution, rather than trying to immediately recover the situation by
>>    sending a STOP command.
>>
> 
> I'm wondering if just enable this quirk on exynos too is the proper
> solution. Unfortunately I don't have enough documentation to check
> differences between those controllers.
> Also will really help have access to some hardware that uses
> dw_mmc-pltfm to check if, like on exynos, same issue is triggered.
> Anyone with the hardware who can do some tests?

I want to remove all quirks for dwmmc controller. (in progressing with Shawn.)

> 
> 
>> Maybe dw-mmc can do something similar, but with the lack of data transfer
>> timeout, maybe it's possible to do something with a kernel timer instead,
>> and check what the hardware is doing after a response CRC error?
>>
>> --
>> RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/
>> FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
>> according to speedtest.net.
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