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From:   Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Date:   Mon, 21 Mar 2022 20:39:59 +0300
Message-ID: <CAA8EJpribc722wN2jR5sQEkX6FiaE_SdBk8B5HPamCXZWhEd7A@mail.gmail.com>
Subject: Re: [PATCH v6 1/5] drm/msm/disp/dpu1: set mdp clk to the maximum
 frequency in opp table during probe
To:     Vinod Polimera <vpolimer@qti.qualcomm.com>
Cc:     Stephen Boyd <swboyd@chromium.org>,
        quic_vpolimer <quic_vpolimer@quicinc.com>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "dri-devel@lists.freedesktop.org" <dri-devel@lists.freedesktop.org>,
        "freedreno@lists.freedesktop.org" <freedreno@lists.freedesktop.org>,
        "linux-arm-msm@vger.kernel.org" <linux-arm-msm@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "robdclark@gmail.com" <robdclark@gmail.com>,
        "dianders@chromium.org" <dianders@chromium.org>,
        quic_kalyant <quic_kalyant@quicinc.com>
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On Mon, 21 Mar 2022 at 19:21, Vinod Polimera <vpolimer@qti.qualcomm.com> wrote:
>
>
>
> > -----Original Message-----
> > From: Stephen Boyd <swboyd@chromium.org>
> > Sent: Friday, March 18, 2022 2:41 AM
> > To: quic_vpolimer <quic_vpolimer@quicinc.com>;
> > devicetree@vger.kernel.org; dri-devel@lists.freedesktop.org;
> > freedreno@lists.freedesktop.org; linux-arm-msm@vger.kernel.org
> > Cc: linux-kernel@vger.kernel.org; robdclark@gmail.com;
> > dmitry.baryshkov@linaro.org; dianders@chromium.org; quic_kalyant
> > <quic_kalyant@quicinc.com>
> > Subject: Re: [PATCH v6 1/5] drm/msm/disp/dpu1: set mdp clk to the
> > maximum frequency in opp table during probe
> >
> > WARNING: This email originated from outside of Qualcomm. Please be wary
> > of any links or attachments, and do not enable macros.
> >
> > Quoting Vinod Polimera (2022-03-14 07:46:53)
> > > use max clock during probe/bind sequence from the opp table.
> > > The clock will be scaled down when framework sends an update.
> >
> > Capitalize 'use'.
> >
> > Why is it important to use max frequency during probe/bind? Does not
> > setting the clk rate during probe mean that we'll never use the max
> > rate? Does it speed things up during probe?
>
> We need to vote mdp clock during probe/bind so that rails are not set at undetermined state as pointed out by Dmitry.
> Since we dont know what will be the rate set in boot loader, it would be ideal to vote at max frequency.
> There could be a firmware display programmed in bootloader and we want to transition it to kernel without underflowing.

This should be expressed in the commit message.


-- 
With best wishes
Dmitry