linux-kernel - Re: [RFC PATCH 2/2] ARM: EXYNOS: Make sure that the Exynos5420 MDMA0 clock is enabled during suspend

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Date:	Fri, 27 Mar 2015 16:15:23 +0100
From:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
CC:	Kukjin Kim <kgene@...nel.org>,
	Doug Anderson <dianders@...omium.org>,
	Olof Johansson <olof@...om.net>,
	Abhilash Kesavan <kesavan.abhilash@...il.com>,
	Kevin Hilman <khilman@...aro.org>,
	Tyler Baker <tyler.baker@...aro.org>,
	Steve Capper <steve.capper@...aro.org>,
	Amit Kucheria <amit.kucheria@...aro.org>,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 2/2] ARM: EXYNOS: Make sure that the Exynos5420 MDMA0
 clock is enabled during suspend

Hello Krzysztof,

Thanks a lot for your feedback.

On 03/27/2015 03:38 PM, Krzysztof Kozlowski wrote:
> 2015-03-27 15:21 GMT+01:00 Javier Martinez Canillas
> <javier.martinez@...labora.co.uk>:
>> Commit ae43b3289186 ("ARM: 8202/1: dmaengine: pl330: Add runtime Power
>> Management support v12") added pm support for the pl330 dma driver but
>> it makes the clock for the Exynos5420 MDMA0 DMA controller to be gated
>> during suspend and this clock needs to remain enabled in order to make
>> the system resume from a system suspend state.
>>
>> To make sure that the clock is enabled during suspend, enable it prior
>> to entering a suspend state and disable it once the system has resumed.
>>
>> Thanks to Abhilash Kesavan for figuring out that this was the issue.
>>
>> Fixes: ae43b32 ("ARM: 8202/1: dmaengine: pl330: Add runtime Power Management support v12")
>> Signed-off-by: Javier Martinez Canillas <javier.martinez@...labora.co.uk>
> 
> Hmmm... isn't a real problem elsewhere - like some clock hierarchy is
> wrong or incomplete? This rather looks like workaround for the
> problem.
>

That's a very good question, that's why I sent it as an RFC. I didn't find
anything relevant in the manual but I could certainly be missing something.

>>
>> @@ -516,6 +528,9 @@ static void exynos5420_pm_resume(void)
>>  {
>>         unsigned long tmp;
>>
>> +       if (!IS_ERR_OR_NULL(clk))
>> +               clk_disable_unprepare(clk);
>> +
> 
> Missing clk_put()
>

Yes, Sylwester already pointed it out. Sorry for missing that.
 
> Best regards,
> Krzysztof
> 

Best regards,
Javier
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