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

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Date:   Mon, 31 Aug 2020 10:19:06 +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 10:11:02AM +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).

Best regards,
Krzysztof