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    SubjectRe: [PATCH v2 2/3] drm/msm/dp: do not re initialize of audio_comp at display_disable()
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    Quoting Kuogee Hsieh (2021-04-13 16:11:30)
    > At dongle unplug, dp initializes audio_comp followed by sending disconnect
    > event notification to audio and to make sure audio had shutdown completely
    > by wait for audio completion notification at display_disable(). This patch

    Is this dp_display_disable()? Doubtful that display_disable() is the
    function we're talking about.

    > will not re initialize audio_comp at display_disable() if audio shutdown
    > is triggered by dongle unplugged.

    This commit text seems to say the why before the what, where why is "dp
    initializes audio_comp followed by sending disconnect.." and the what is
    "this patch will no re-initialized audio_comp...". Can you reorder this
    so the what comes before the why?

    >
    > Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>
    > ---
    > drivers/gpu/drm/msm/dp/dp_display.c | 6 ++++--
    > 1 file changed, 4 insertions(+), 2 deletions(-)
    >
    > diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
    > index 0ba71c7..1d71c95 100644
    > --- a/drivers/gpu/drm/msm/dp/dp_display.c
    > +++ b/drivers/gpu/drm/msm/dp/dp_display.c
    > @@ -894,8 +894,10 @@ static int dp_display_disable(struct dp_display_private *dp, u32 data)
    > /* wait only if audio was enabled */
    > if (dp_display->audio_enabled) {
    > /* signal the disconnect event */
    > - reinit_completion(&dp->audio_comp);
    > - dp_display_handle_plugged_change(dp_display, false);
    > + if (dp->hpd_state != ST_DISCONNECT_PENDING) {
    > + reinit_completion(&dp->audio_comp);

    Why is this reinitialized here at all? Wouldn't it make more sense to
    initialize the completion once at cable plug in and then not initialize
    the completion anywhere else? Or initialize the completion whenever
    dp_display->audio_enabled is set to true and then only wait for the
    completion here if that boolean is true? Or initialize the completion
    when dp_display_handle_plugged_change() is passed true for the 'plugged'
    argument?

    I started reading the code and quickly got lost figuring out how
    dp_display_handle_plugged_change() worked and the interaction between
    the dp display code and the audio codec embedded in here. There seem to
    be a couple of conditions that cut off things early, like
    dp_display->audio_enabled and audio->engine_on. Why? Why does
    dp_display_signal_audio_complete() call complete_all() vs. just
    complete()? Please help! :(

    > + dp_display_handle_plugged_change(dp_display, false);

    I think it's this way because dp_hpd_unplug_handle() is the function
    that sets the hpd_state to ST_DISCONNECT_PENDING and then reinitializes
    the completion (why?) and calls dp_display_handle_plugged_change(). So
    the commit text could say that reinitializing the completion again here
    at dp_display_disable() is racing with the audio code in the case that
    dp_hpd_unplug_handle() already called
    dp_display_handle_plugged_change() and it would make more sense. But the
    question still stands why that race even exists in the first place vs.
    initializing the completion variable in only one place unconditionally
    when the cable is connected, in dp_hpd_plug_handle() or
    dp_display_post_enable().

    > + }
    > if (!wait_for_completion_timeout(&dp->audio_comp,
    > HZ * 5))
    > DRM_ERROR("audio comp timeout\n");

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