linux-kernel - Re: [PATCH AUTOSEL 6.2 18/60] drm/msm/dp: Remove INIT

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Date:   Mon, 27 Feb 2023 10:12:20 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Sasha Levin <sashal@...nel.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Bjorn Andersson <quic_bjorande@...cinc.com>,
        Kuogee Hsieh <quic_khsieh@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        robdclark@...il.com, quic_abhinavk@...cinc.com, airlied@...il.com,
        daniel@...ll.ch, swboyd@...omium.org, johan+linaro@...nel.org,
        quic_sbillaka@...cinc.com, linux-arm-msm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org
Subject: Re: [PATCH AUTOSEL 6.2 18/60] drm/msm/dp: Remove INIT_SETUP delay

On Sun, Feb 26, 2023 at 09:00:03PM -0500, Sasha Levin wrote:
> From: Bjorn Andersson <quic_bjorande@...cinc.com>
> 
> [ Upstream commit e17af1c9d861dc177e5b56009bd4f71ace688d97 ]
> 
> During initalization of the DisplayPort controller an EV_HPD_INIT_SETUP
> event is generated, but with a delay of 100 units. This delay existed to
> circumvent bug in the QMP combo PHY driver, where if the DP part was
> powered up before USB, the common properties would not be properly
> initialized - and USB wouldn't work.
> 
> This issue was resolved in the recent refactoring of the QMP driver,
> so it's now possible to remove this delay.
> 
> While there is still a timing dependency in the current implementation,
> test indicates that it's now possible to boot with an external display
> on USB Type-C and have the display power up, without disconnecting and
> reconnecting the cable.
>
> Signed-off-by: Bjorn Andersson <quic_bjorande@...cinc.com>
> Reviewed-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
> Patchwork: https://patchwork.freedesktop.org/patch/518729/
> Link: https://lore.kernel.org/r/20230117172951.2748456-1-quic_bjorande@quicinc.com
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> Signed-off-by: Sasha Levin <sashal@...nel.org>

This is not a bug fix and should not be backported.

Johan