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From:   Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Date:   Tue, 5 Apr 2022 00:13:03 +0300
Message-ID: <CAA8EJpqOzn4xh1N9GhEbH6YY5uHPdeqhiDnSNMM+ZQ3GdaWFrA@mail.gmail.com>
Subject: Re: [PATCH v6 6/8] drm/msm/dp: remove unnecessary delay during boot
To:     "Sankeerth Billakanti (QUIC)" <quic_sbillaka@quicinc.com>
Cc:     Doug Anderson <dianders@chromium.org>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        freedreno <freedreno@lists.freedesktop.org>,
        LKML <linux-kernel@vger.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>, Rob Clark <robdclark@gmail.com>,
        Sean Paul <seanpaul@chromium.org>,
        Stephen Boyd <swboyd@chromium.org>,
        quic_kalyant <quic_kalyant@quicinc.com>,
        "Abhinav Kumar (QUIC)" <quic_abhinavk@quicinc.com>,
        "Kuogee Hsieh (QUIC)" <quic_khsieh@quicinc.com>,
        "bjorn.andersson@linaro.org" <bjorn.andersson@linaro.org>,
        Sean Paul <sean@poorly.run>, David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        quic_vproddut <quic_vproddut@quicinc.com>,
        "Aravind Venkateswaran (QUIC)" <quic_aravindh@quicinc.com>
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On Mon, 4 Apr 2022 at 16:53, Sankeerth Billakanti (QUIC)
<quic_sbillaka@quicinc.com> wrote:
>
> Hi Doug,
>
> > On Wed, Mar 30, 2022 at 9:04 AM Sankeerth Billakanti
> > <quic_sbillaka@quicinc.com> wrote:
> > >
> > > Remove the unnecessary delay in executing the EV_HPD_INIT_SETUP
> > event.
> >
> > Tell me more and put it in the commit message! Why did it used to be
> > necessary and why is it no longer necessary? Inquiring minds want to know.
> >
>
> Okay. I will add proper description. The DP phy is shared with usb and executing the
> dp phy_init before the usb phy_init was causing usb devices to not function.

I always wondered, how does this work for the 4-lane DP dongles, where
there is no USB mode/lanes?

> Earlier, enabling phy_init was done when the EV_HPD_INIT_SETUP event was executed.
> So, we had scheduled it to execute after 10 second to let the usb driver complete the phy_init first.
>
> Kuogee made the below change to move the DP phy_init to execute after the DP is connected
> https://patchwork.kernel.org/project/linux-arm-msm/patch/1642531648-8448-2-git-send-email-quic_khsieh@quicinc.com/
>
> So, there is no need for the DP driver to wait 10 seconds for the phy initialization anymore.
>
> eDP PHY is not shared with usb. So, it can be programmed anytime, hence not needing any delay.


-- 
With best wishes
Dmitry