linux-kernel - Re: [PATCH v3 6/6] drm/msm/dp: do not end dp link training until video is ready

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Message-ID: <CAE-0n52n6ypCLrA3mWHekh9Caq8rT5ngV2X5MWdGYA8DJQb92g@mail.gmail.com>
Date:   Tue, 10 Aug 2021 14:35:54 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Kuogee Hsieh <khsieh@...eaurora.org>,
        dri-devel@...ts.freedesktop.org, robdclark@...il.com,
        sean@...rly.run
Cc:     abhinavk@...eaurora.org, aravindh@...eaurora.org, airlied@...ux.ie,
        daniel@...ll.ch, bjorn.andersson@...aro.org,
        linux-arm-msm@...r.kernel.org, freedreno@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 6/6] drm/msm/dp: do not end dp link training until
 video is ready

Quoting Kuogee Hsieh (2021-08-05 13:44:55)
> Initialize both pre-emphasis and voltage swing level to 0 before
> start link training and do not end link training until video is
> ready to reduce the period between end of link training and video
> start to meet Link Layer CTS requirement.  Some dongle main link
> symbol may become unlocked again if host did not end link training
> soon enough after completion of link training 2. Host have to re
> train main link if loss of symbol locked detected before end link
> training so that the coming video stream can be transmitted to sink
> properly. This fixes Link Layer CTS cases 4.3.2.1, 4.3.2.2, 4.3.2.3
> and 4.3.2.4.
>
> Changes in v3:
> -- merge retrain link if loss of symbol locked happen into this patch
> -- replace dp_ctrl_loss_symbol_lock() with dp_ctrl_channel_eq_ok()
>
> Signed-off-by: Kuogee Hsieh <khsieh@...eaurora.org>
> ---

Reviewed-by: Stephen Boyd <swboyd@...omium.org>