linux-kernel - Re: [PACTH v3] mmc: sdhci: Do not allow tuning procedure to be interrupted

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Date:	Thu, 18 Aug 2016 16:46:49 +0300
From:	Adrian Hunter <adrian.hunter@...el.com>
To:	Christopher Freeman <cfreeman@...dia.com>,
	Robert Foss <robert.foss@...labora.com>
Cc:	ulf.hansson@...aro.org, linux-mmc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Andrew Bresticker <abrestic@...omium.org>,
	Kevin Cernekee <cernekee@...omium.org>,
	Benson Leung <bleung@...omium.org>
Subject: Re: [PACTH v3] mmc: sdhci: Do not allow tuning procedure to be
 interrupted

On 18/08/16 01:12, Christopher Freeman wrote:
> On 08-17 01:31 PM, Robert Foss wrote:
>>
>>
>> On 2016-08-17 06:47 AM, Adrian Hunter wrote:
>>> On 17/08/16 00:25, robert.foss@...labora.com wrote:
>>>> From: Christopher Freeman <cfreeman@...dia.com>
>>>>
>>>> wait_event_interruptible_timeout() will return early if the blocked
>>>> process receives a signal, causing the driver to abort the tuning
>>>> procedure and possibly leaving the controller in a bad state.  Since the
>>>> tuning command is expected to complete quickly (<50ms) and we've set a
>>>> timeout, use wait_event_timeout() instead.
>>>>
>>>> Signed-off-by: Christopher Freeman <cfreeman@...dia.com>
>>>> Tested-by: Robert Foss <robert.foss@...labora.com>
>>>> Signed-off-by: Robert Foss <robert.foss@...labora.com>
>>>> Reviewed-by: Benson Leung <bleung@...omium.org>
>>>
>>> The mmc block queues are kernel threads which I would expect ignore signals,
>>> so I am curious how you hit this?
>>
>> The issue was discovered on (tegra2?) hardware that is sensitive to
>> being interrupted during tuning and having the controller left in a
>> sensitive state.
>>
>> @Christopher Freeman: Maybe you can provide us with some additional details?
>>
> 
> It was found with Tegra 210.  The signalling was an issue because tuning was
> kicked off from an ioctl to the wifi device on the controller.
> 
> FWIW, this issue was particular to the wifi driver (bcmdhd) and the android
> tree.   It in part depends on the way the wifi driver is able to reset the
> sdio device via a routine that's not present in mainline: sdio_reset_comm.
> I believe the wifi driver would power on the wifi chip and trigger tuning in
> the aforementioned ioctl.  Process that sent the ioctl was some network or wifi
> manager service on Android.
> 
> Let me know if you would like any more details.

Thanks for the explanation.

> 
>>>
>>> In any case:
>>>
>>> Acked-by: Adrian Hunter <adrian.hunter@...el.com>
>>>
>