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Date: Wed, 26 Jun 2013 22:57:13 +0200
Message-ID: <CAPDyKFpKYeqoFn=S6P2tu1s2C28daCh4vcHTUCCRUOx2_MHShg@mail.gmail.com>
Subject: Re: [RFC PATCH] mmc: Enable wakeup_sources for mmc core
From: Ulf Hansson <ulf.hansson@linaro.org>
To: Zoran Markovic <zoran.markovic@linaro.org>
Cc: Colin Cross <ccross@android.com>, lkml <linux-kernel@vger.kernel.org>,
        linux-mmc@vger.kernel.org, San Mehat <san@google.com>,
        John Stultz <john.stultz@linaro.org>, Chris Ball <cjb@laptop.org>,
        Johan Rudholm <johan.rudholm@stericsson.com>,
        Jaehoon Chung <jh80.chung@samsung.com>,
        Konstantin Dorfman <kdorfman@codeaurora.org>,
        Guennadi Liakhovetski <g.liakhovetski@gmx.de>,
        Tejun Heo <tj@kernel.org>, Andrew Morton <akpm@linux-foundation.org>
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On 24 June 2013 21:58, Zoran Markovic <zoran.markovic@linaro.org> wrote:
>>> This patch is ported from the Android common tree, so you've probably
>>> been using it.
>>
>> We removed more or less all Android code in the mmc subsystem, since
>> it just didn't work. :-)
>>
>> The "deferred resume" was very useful though, so after some rework we
>> kept it and could then improve the system resume time significantly.
>
> For what it's worth, I fixed one bug I noticed in the Android kernel:
> if a system has a non-removable MMC device, a suspend/resume cycle on
> this device would hold a wake lock forever. This was a visible issue
> on the panda board I am using.
>
> If there are doubts on whether or not the system should stay awake
> during a MMC mount, we have the option to make the calls to
> wakeup_source_register/unregister configurable. Skipping these calls
> would leave the .ws field NULL, in which case
> __pm_stay_awake/__pm_relax/__pm_wakeup_event would do nothing.

Even if we make this feature configurable, I can't see any host driver
that would benefit from it as of today. The reason is simply that host
drivers do not configure it's card detect irq as a wakeup irq. Myself
is also having quite hard to see the benefit of doing that, but I
don't know all the use cases.

Let's see if we can get someone else to provide input...

>
> Thoughts?
>
> - Zoran


Kind regards
Ulf Hansson
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