linux-kernel - Re: [PATCH v3] drm/msm/dp: check hpd_state before push idle pattern at dp_bridge

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Date:   Wed, 10 Aug 2022 17:22:52 -0500
From:   Stephen Boyd <swboyd@...omium.org>
To:     Kuogee Hsieh <quic_khsieh@...cinc.com>, agross@...nel.org,
        airlied@...ux.ie, bjorn.andersson@...aro.org, daniel@...ll.ch,
        dianders@...omium.org, dmitry.baryshkov@...aro.org,
        robdclark@...il.com, sean@...rly.run, vkoul@...nel.org
Cc:     quic_abhinavk@...cinc.com, quic_aravindh@...cinc.com,
        quic_sbillaka@...cinc.com, freedreno@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] drm/msm/dp: check hpd_state before push idle pattern
 at dp_bridge_disable()

Quoting Kuogee Hsieh (2022-08-10 12:25:51)
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index b36f8b6..678289a 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -1729,10 +1729,20 @@ void dp_bridge_disable(struct drm_bridge *drm_bridge)
>         struct msm_dp_bridge *dp_bridge = to_dp_bridge(drm_bridge);
>         struct msm_dp *dp = dp_bridge->dp_display;
>         struct dp_display_private *dp_display;
> +       u32 state;
>
>         dp_display = container_of(dp, struct dp_display_private, dp_display);
>
> +       mutex_lock(&dp_display->event_mutex);
> +
> +       state = dp_display->hpd_state;
> +       if (state != ST_DISCONNECT_PENDING && state != ST_CONNECTED) {

It's concerning that we have to check this at all. Are we still
interjecting into the disable path when the cable is disconnected?

> +               mutex_unlock(&dp_display->event_mutex);
> +               return;
> +       }
> +
>         dp_ctrl_push_idle(dp_display->ctrl);
> +       mutex_unlock(&dp_display->event_mutex);