linux-kernel - Re: [PATCH v4 7/7] RFC: drm/panfrost: devfreq: Add support for 2 regulators

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Message-ID: <CANMq1KCD-Ut3bjEmtpPCgOf+KHyi9cw7QSsxcQrWU4h2juZCUQ@mail.gmail.com>
Date:   Thu, 13 Feb 2020 16:24:59 +0800
From:   Nicolas Boichat <drinkcat@...omium.org>
To:     Rob Herring <robh+dt@...nel.org>
Cc:     David Airlie <airlied@...ux.ie>, Daniel Vetter <daniel@...ll.ch>,
        Mark Rutland <mark.rutland@....com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        Steven Price <steven.price@....com>,
        Alyssa Rosenzweig <alyssa.rosenzweig@...labora.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Devicetree List <devicetree@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>
Subject: Re: [PATCH v4 7/7] RFC: drm/panfrost: devfreq: Add support for 2 regulators

On Thu, Feb 13, 2020 at 3:57 PM Nicolas Boichat <drinkcat@...omium.org> wrote:
> > > [snip]
> > > But then there's a slight problem: panfrost_devfreq uses a bunch of
> > > clk_get_rate calls, and the clock PLLs (at least on MTK platform) are
> > > never fully precise, so we get back 299999955 for 300 Mhz and
> > > 799999878 for 800 Mhz. That means that the kernel is unable to keep
> > > devfreq stats as neither of these values are in the table:
> > > [ 4802.470952] devfreq devfreq1: Couldn't update frequency transition
> > > information.
> > > The kbase driver fixes this by remembering the last set frequency, and
> > > reporting that to devfreq. Should we do that as well or is there a
> > > better fix?

This one is my bad, I was missing this patch in my forklift to 4.19:
22bd4df9dadf46f drm/panfrost: devfreq: Round frequencies to OPPs

(should really try to boot that board on linux-next, but that's for
another time)