linux-kernel - Re: [PATCH 1/3] clk: exynos-audss: Keep the parent of mout

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Message-ID: <53AA3D71.5010000@gmail.com>
Date:	Wed, 25 Jun 2014 08:39:37 +0530
From:	Tushar Behera <trblinux@...il.com>
To:	Doug Anderson <dianders@...gle.com>,
	Tushar Behera <tushar.b@...sung.com>
CC:	Kevin Hilman <khilman@...aro.org>,
	lkml <linux-kernel@...r.kernel.org>,
	ML Devicetree <devicetree@...r.kernel.org>,
	linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
	ML Arch-Arm <linux-arm-kernel@...ts.infradead.org>,
	Mike Turquette <mturquette@...aro.org>,
	Tomasz Figa <t.figa@...sung.com>,
	Russell King <linux@....linux.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Mark Rutland <mark.rutland@....com>,
	Pawel Moll <pawel.moll@....com>,
	Rob Herring <robh+dt@...nel.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Shaik Ameer Basha <shaik.ameer@...sung.com>
Subject: Re: [PATCH 1/3] clk: exynos-audss: Keep the parent of mout_audss
 always enabled

On 06/25/2014 04:29 AM, Doug Anderson wrote:
> Tushar,
> 
> On Thu, Jun 12, 2014 at 12:40 AM, Tushar Behera <tushar.b@...sung.com> wrote:
>> On Wed, Jun 11, 2014 at 10:20 PM, Kevin Hilman <khilman@...aro.org> wrote:
>>> Tushar Behera <tushar.b@...sung.com> writes:
>>>
>>>> When the output clock of AUDSS mux is disabled, we are getting kernel
>>>> oops while doing a clk_get() on other clocks provided by AUDSS.
>>>>
>>>> Though user manual doesn't specify this dependency, we came across
>>>> this issue while disabling the parent of AUDSS mux clocks.
>>>>
>>>> Keeping the parents of AUDSS mux always enabled fixes this issue.
>>>
>>> While this patch works (and fixes the boot problem for me), it seems
>>> like it's papering over the real problem.
>>>
>>
>> Thanks for testing.
>>
>>> Seems like the right fix is actually modelling the clocks properly so
>>> that enabling a child clock ensures that the parent is also enabled.
>>>
>>
>> Patch 2/3 was to ensure we have proper clock tree defined for
>> Exynos5420. While testing with audio disabled, that patch alone fixed
>> the issue. But when audio was enabled (and hence I2S0 was trying to
>> access the clocks), we got some kernel oops during late booting, hence
>> I came up this solution.
>>
>> The solution might be a little half-baked because of the urgency to
>> push the fix, but will try to dig more into the issue on Monday when I
>> resume office.
> 
> Which Monday were you referring to?  ;)
> 

Sorry that I couldn't get deeper into this issue. Thanks for reminding
though.

> ...but in all seriousness do you have an official status update on
> this patch?  It seems as if it's not needed and all you need is
> <https://patchwork.kernel.org/patch/4333581/>, but it would be nice to
> get an official confirmation.

I have tested various scenarios with only patch 2/3, which seems to be
sufficient for the time being. I have not encountered the older issue
till now. I was thinking of testing a bit further, but given that you
have already asked for, we can go ahead with only patch 2/3 right now.

In case any further issue comes up, I will post patch 1/3 as per the
review comments that I have got.

> 
> Thanks!
> 
> -Doug
> --
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> 


-- 
Tushar Behera
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