linux-kernel - Re: [RFT 3/4] ARM: dts: exynos: Move CMU assigned ISP clocks to buses in Exynos3250

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Message-ID: <20200831083122.GA12874@kozik-lap>
Date:   Mon, 31 Aug 2020 10:31:22 +0200
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Sam Ravnborg <sam@...nborg.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Kukjin Kim <kgene@...nel.org>,
        Hoegeun Kwon <hoegeun.kwon@...sung.com>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Sylwester Nawrocki <snawrocki@...nel.org>
Subject: Re: [RFT 3/4] ARM: dts: exynos: Move CMU assigned ISP clocks to
 buses in Exynos3250

On Mon, Aug 31, 2020 at 10:19:06AM +0200, Krzysztof Kozlowski wrote:
> On Mon, Aug 31, 2020 at 10:11:02AM +0200, Marek Szyprowski wrote:
> > Hi Krzysztof,
> > 
> > On 29.08.2020 19:25, Krzysztof Kozlowski wrote:
> > > Commit 52005dece527 ("ARM: dts: Add assigned clock parents to CMU node
> > > for exynos3250") added assigned clocks under Clock Management Unit to
> > > fix hangs when accessing ISP registers.
> > >
> > > This is not the place for it as CMU does not have a required "clocks"
> > > property:
> > >
> > >    arch/arm/boot/dts/exynos3250-artik5-eval.dt.yaml: clock-controller@...30000: 'clocks' is a dependency of 'assigned-clocks'
> > >
> > > Signed-off-by: Krzysztof Kozlowski <krzk@...nel.org>
> > >
> > > ---
> > >
> > > Not tested and I wonder whether actually correct. For example, what will
> > > happen if devfreq (exynos-bus) is not built in?
> > >
> > > Could someone verify it?
> > 
> > Sorry, but this patch is not correct. Those clocks has noting with 
> > bus-freq. The assigned clocks property should stay where it is. Maybe 
> > one need to fix the schemas for dts verification. Those clocks has to be 
> > set (and so generic clock framework does) according to the assigned 
> > clocks properties once the clock controller is instantiated.
> > 
> > The only alternative would be to add exynos-subcmu variant to properly 
> > link CMU with the ISP power domain, but assuming that there is no Exynos 
> > 3250 ISP driver in mainline (and probably never will be), it is safe to 
> > keep those clocks sourced from 24MHz crystal.
> 
> Thanks for the clarification.  Another solution to silence the warning
> could be to add a "clocks" property for FIN_PLL, although the driver
> actually does not take it.
> 
> This is the only remaining dtschema check warning on Exynos3250 so it
> would be nice to at least silence it. My goal is to have all them
> schema-correct, or as close as possible (for Exynos4 the camera node is
> a trouble).

BTW, if you have some time, it would be awesome if you could test all
the series (on Exynos3250 obviously with this patch reverted):
https://github.com/krzk/linux/tree/for-next/dts-exynos-schema-cleanups

The Exynos5 cleanup is ongoing, so there will be more patches. But
Exynos3 and Exynos4 I finished.

Best regards,
Krzysztof