linux-kernel - Re: [PATCH 2/2] ARM: dts: exynos: Use correct mfc

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Message-ID: <55cdceb9-d768-d5a9-7bc2-d4ef26d2e5e8@osg.samsung.com>
Date:   Fri, 20 Jan 2017 14:15:40 -0300
From:   Javier Martinez Canillas <javier@....samsung.com>
To:     Krzysztof Kozlowski <krzk@...nel.org>
Cc:     linux-kernel@...r.kernel.org, Inki Dae <inki.dae@...sung.com>,
        Andi Shyti <andi.shyti@...sung.com>,
        Shuah Khan <shuahkh@....samsung.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Andrzej Hajda <a.hajda@...sung.com>,
        devicetree@...r.kernel.org, Kukjin Kim <kgene@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        linux-samsung-soc@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/2] ARM: dts: exynos: Use correct mfc_pd async-bridge
 clock for Exynos5420

Hello Krzysztof,

On 01/20/2017 01:28 PM, Krzysztof Kozlowski wrote:
> On Thu, Jan 19, 2017 at 07:29:55PM -0300, Javier Martinez Canillas wrote:
>> Commit 94aed538e032 ("ARM: dts: exynos: Add async-bridge clock to MFC
>> power domain for Exynos5420") fixed an imprecise external abort error
>> when the MFC registers were tried to be accessed and the needed clock
>> for the asynchronous bridges were gated.
>>
>> But according to the Exynos5420 manual the "Gating AXI clock for MFC"
>> is not CLK_ACLK333 but CLK_MFC.
>>
>> The end effect is the same because CLK_ACLK333 is a parent of CLK_MFC
>> but the correct clock should be used instead.
>>
>> Signed-off-by: Javier Martinez Canillas <javier@....samsung.com>
>>
>> ---
>>
>>  arch/arm/boot/dts/exynos5420.dtsi | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Is this still needed?
> 

Not really, only if we care about correctness in the existing power domains
that have their clocks defined. But as said, even currently with CLK_ACLK333
works due to the clock hierarchy.

I think is less of an issue now that we prefer to mark clocks that needs to
be ungated as critical instead of growing the DT ABI.

> Best regards,
> Krzysztof
> 
 
Best regards,
-- 
Javier Martinez Canillas
Open Source Group
Samsung Research America