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

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Date:   Fri, 20 Jan 2017 19:32:26 +0200
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Javier Martinez Canillas <javier@....samsung.com>
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

On Fri, Jan 20, 2017 at 02:15:40PM -0300, Javier Martinez Canillas wrote:
> 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.

Okay then, I'll skip the patch. Resend if it turns out to be needed.


Best regards,
Krzysztof