From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tomasz Figa <t.figa@samsung.com>
Subject: Re: sdhci_s3c_consider_clock scheduling while atomic - clk_round_rate
Date: Tue, 24 Jun 2014 17:52:21 +0200
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To: Daniel Drake <drake@endlessm.com>, linux-samsung-soc <linux-samsung-soc@vger.kernel.org>
Cc: linux-mmc@vger.kernel.org, ben-linux@fluff.org, Tomasz Figa <tomasz.figa@gmail.com>, Ulf Hansson <ulf.hansson@linaro.org>, Chris Ball <chris@printf.net>, Mike Turquette <mturquette@linaro.org>
List-Id: linux-mmc@vger.kernel.org

Hi Daniel,

[adding Ulf, Chris and Mike to the discussion]

On 24.06.2014 11:48, Daniel Drake wrote:
> sdhci_s3c_set_clock is called from sdhci_do_set_ios with interrupts
> disabled, and this calls into sdhci_s3c_consider_clock().
> 
> The patch "mmc: sdhci-s3c: Cache bus clock rates" addressed some
> scheduling while atomic in this function, but there are more issues
> here, seen while testing 3.16-rc2 on exynos4412:
> 
> BUG: sleeping function called from invalid context at kernel/locking/mutex.c:103
> in_atomic(): 1, irqs_disabled(): 128, pid: 75, name: mmcqd/0
> Preemption disabled at:[<  (null)>]   (null)
> 
> CPU: 0 PID: 75 Comm: mmcqd/0 Not tainted 3.16.0-rc2-00028-ge9fe7eb-dirty #77
> [<c0016140>] (unwind_backtrace) from [<c0011e14>] (show_stack+0x10/0x14)
> [<c0011e14>] (show_stack) from [<c05ce8a8>] (dump_stack+0x84/0xc4)
> [<c05ce8a8>] (dump_stack) from [<c05d2de0>] (mutex_lock+0x1c/0x3c)
> [<c05d2de0>] (mutex_lock) from [<c046214c>] (clk_prepare_lock+0x6c/0xf4)
> [<c046214c>] (clk_prepare_lock) from [<c04625ac>] (clk_round_rate+0x10/0x2c)
> [<c04625ac>] (clk_round_rate) from [<c0447628>] (sdhci_s3c_set_clock+0x4c/0x1e8)
> [<c0447628>] (sdhci_s3c_set_clock) from [<c0447818>]
> (sdhci_cmu_set_clock+0x54/0x140)
> [<c0447818>] (sdhci_cmu_set_clock) from [<c0443a38>]
> (sdhci_do_set_ios+0x138/0x58c)
> [<c0443a38>] (sdhci_do_set_ios) from [<c0443864>] (sdhci_set_ios+0x28/0x34)
> 
> clk_round_rate cannot be called here because it takes a mutex.
> 
> sdhci_s3c_set_clock() also calls into clk_prepare_enable() which looks
> like it could trigger this problem too.

Apparently this is related to generic sdhci code calling .set_clock()
under spin_lock_irqsave(). For reference, see sdhci_do_set_ios() and
sdhci_tasklet_finish().

Chris, Ulf, any suggestions?

Best regards,
Tomasz