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

This reverts commit e467e0bd ("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: e467e0bd ("drm/msm/dp: use drm_bridge_hpd_notify() to report HPD status changes")
Link: https://gitlab.freedesktop.org/drm/msm/-/issues/50Reported-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/Zd3YPGmrprxv-N-O@hovoldconsulting.com/Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Tested-by: Paloma Arellano <quic_parellan@quicinc.com>
Tested-by: Johan Hovold <johan+linaro@kernel.org>
Tested-by: Neil Armstrong <neil.armstrong@linaro.org> # on SM8650-HDK
Patchwork: https://patchwork.freedesktop.org/patch/580313/
Link: https://lore.kernel.org/r/20240227220808.50146-1-dmitry.baryshkov@linaro.org

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;
 }