[PATCH] Revert "drm/msm/dp: use drm_bridge_hpd_notify() to report HPD status changes"

[neil.armstrong at linaro.org]

On 27/02/2024 23:08, Dmitry Baryshkov wrote:
> This reverts commit e467e0bde881 ("drm/msm/dp: use
> drm_bridge_hpd_notify() to report HPD status changes").
> 
> The commit changed the way how the MSM DP driver communicates
> HPD-related events to the userspace. The mentioned commit made some of
> the HPD events being reported earlier. This way userspace starts poking
> around. It interacts in a bad way with the dp_bridge_detect and the
> driver's state machine, ending up either with the very long delays
> during hotplug detection or even inability of the DP driver to report
> the display as connected.
> 
> A proper fix will involve redesigning of the HPD handling in the MSM DP
> driver. It is underway, but it will be intrusive and can not be thought
> about as a simple fix for the issue. Thus, revert the offending commit.
> 
> Fixes: e467e0bde881 ("drm/msm/dp: use drm_bridge_hpd_notify() to report HPD status changes")
> Link: https://gitlab.freedesktop.org/drm/msm/-/issues/50
> Reported-by: Johan Hovold <johan at kernel.org>
> Link: https://lore.kernel.org/r/Zd3YPGmrprxv-N-O@hovoldconsulting.com/
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov at linaro.org>
> ---
>   drivers/gpu/drm/msm/dp/dp_display.c | 20 ++++++++++++++++++--
>   1 file changed, 18 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index d37d599aec27..4c72124ffb5d 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -329,10 +329,26 @@ static const struct component_ops dp_display_comp_ops = {
>   	.unbind = dp_display_unbind,
>   };
>   
> +static void dp_display_send_hpd_event(struct msm_dp *dp_display)
> +{
> +	struct dp_display_private *dp;
> +	struct drm_connector *connector;
> +
> +	dp = container_of(dp_display, struct dp_display_private, dp_display);
> +
> +	connector = dp->dp_display.connector;
> +	drm_helper_hpd_irq_event(connector->dev);
> +}
> +
>   static int dp_display_send_hpd_notification(struct dp_display_private *dp,
>   					    bool hpd)
>   {
> -	struct drm_bridge *bridge = dp->dp_display.bridge;
> +	if ((hpd && dp->dp_display.link_ready) ||
> +			(!hpd && !dp->dp_display.link_ready)) {
> +		drm_dbg_dp(dp->drm_dev, "HPD already %s\n",
> +				(hpd ? "on" : "off"));
> +		return 0;
> +	}
>   
>   	/* reset video pattern flag on disconnect */
>   	if (!hpd) {
> @@ -348,7 +364,7 @@ static int dp_display_send_hpd_notification(struct dp_display_private *dp,
>   
>   	drm_dbg_dp(dp->drm_dev, "type=%d hpd=%d\n",
>   			dp->dp_display.connector_type, hpd);
> -	drm_bridge_hpd_notify(bridge, dp->dp_display.link_ready);
> +	dp_display_send_hpd_event(&dp->dp_display);
>   
>   	return 0;
>   }

Tested-by: Neil Armstrong <neil.armstrong at linaro.org> # on SM8650-HDK