linux-kernel - RE: [PATCH v6 6/8] drm/msm/dp: remove unnecessary delay during boot

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Date:   Mon, 4 Apr 2022 13:52:55 +0000
From:   "Sankeerth Billakanti (QUIC)" <quic_sbillaka@...cinc.com>
To:     Doug Anderson <dianders@...omium.org>,
        "Sankeerth Billakanti (QUIC)" <quic_sbillaka@...cinc.com>
CC:     dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, Rob Clark <robdclark@...il.com>,
        Sean Paul <seanpaul@...omium.org>,
        Stephen Boyd <swboyd@...omium.org>,
        quic_kalyant <quic_kalyant@...cinc.com>,
        "Abhinav Kumar (QUIC)" <quic_abhinavk@...cinc.com>,
        "Kuogee Hsieh (QUIC)" <quic_khsieh@...cinc.com>,
        "bjorn.andersson@...aro.org" <bjorn.andersson@...aro.org>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        "dmitry.baryshkov@...aro.org" <dmitry.baryshkov@...aro.org>,
        quic_vproddut <quic_vproddut@...cinc.com>,
        "Aravind Venkateswaran (QUIC)" <quic_aravindh@...cinc.com>
Subject: RE: [PATCH v6 6/8] drm/msm/dp: remove unnecessary delay during boot

Hi Doug,

> On Wed, Mar 30, 2022 at 9:04 AM Sankeerth Billakanti
> <quic_sbillaka@...cinc.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.

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.

> -Doug

Thank you,
Sankeerth