linux-kernel - Re: [PATCH] mmc: tmio: Fix hang during suspend

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Message-ID: <CAPDyKFpyZM8thDhtcw4PUhGPezdag=6Fv_J9nejvenPNdTu-aA@mail.gmail.com>
Date:	Mon, 18 Aug 2014 15:10:53 +0200
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Ian Molton <ian.molton@...ethink.co.uk>
Cc:	Geert Uytterhoeven <geert+renesas@...der.be>,
	Chris Ball <chris@...ntf.net>,
	Linux MMC List <linux-mmc@...r.kernel.org>,
	Linux-sh list <linux-sh@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mmc: tmio: Fix hang during suspend

On 18 August 2014 14:36, Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> Hi Ian,
>
> On Fri, Aug 15, 2014 at 2:49 PM, Ian Molton <ian.molton@...ethink.co.uk> wrote:
>> On Thu, 14 Aug 2014 17:23:53 +0200
>> Geert Uytterhoeven <geert+renesas@...der.be> wrote:
>>
>>> On R-Car Gen 2, the SDHI registers cannot be accessed while the SDHI
>>> module clock is disabled. Doing so will cause a lock-up.
>>>
>>> When suspending, enable the module clock before disabling the SDHI
>>> interrupts, and disable the clock again afterwards.
>>
>> This feels wrong. Why can't interrupts be disabled prior to turning the clock off?
>
> The clock is handled by runtime PM. So if SDHI becomes idle, the clock
> is turned off.
> However, the card insertion interrupt is still enabled.
> If all interrupts would be disabled when the clock is turned off, I believe card
> insertion can no longer be detected.
>
> BTW, I'm still wondering why tmio_mmc_host_resume() works without
> enabling the clock, as it calls tmio_mmc_enable_dma(), which also writes to
> an SDHI register (CTL_DMA_ENABLE).

A while ago, I tried to rework the runtime PM handling of tmio.

http://www.spinics.net/lists/linux-mmc/msg23177.html

The hole set never got merged, due to that we couldn't get them tested
on hardware and there were a lack in review.

We might want to pick them up to see if those may solve our problem. :-)

Kind regards
Uffe

>
>>> This fixes suspend and resume on r8a7791/koelsch.
>>>
>>> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
>>> ---
>>>  drivers/mmc/host/tmio_mmc_pio.c | 10 ++++++++++
>>>  1 file changed, 10 insertions(+)
>>>
>>> diff --git a/drivers/mmc/host/tmio_mmc_pio.c b/drivers/mmc/host/tmio_mmc_pio.c
>>> index faf0924e71cb..83192420a7e3 100644
>>> --- a/drivers/mmc/host/tmio_mmc_pio.c
>>> +++ b/drivers/mmc/host/tmio_mmc_pio.c
>>> @@ -1147,8 +1147,18 @@ int tmio_mmc_host_suspend(struct device *dev)
>>>  {
>>>       struct mmc_host *mmc = dev_get_drvdata(dev);
>>>       struct tmio_mmc_host *host = mmc_priv(mmc);
>>> +     struct tmio_mmc_data *pdata = host->pdata;
>>> +
>>> +     if (pdata->clk_enable) {
>>> +             unsigned int f;
>>> +             pdata->clk_enable(host->pdev, &f);
>>> +     }
>>>
>>>       tmio_mmc_disable_mmc_irqs(host, TMIO_MASK_ALL);
>>> +
>>> +     if (pdata->clk_disable)
>>> +             pdata->clk_disable(host->pdev);
>>> +
>>>       return 0;
>>>  }
>>>  EXPORT_SYMBOL(tmio_mmc_host_suspend);
>>> --
>>> 1.9.1
>
> Gr{oetje,eeting}s,
>
>                         Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds
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