[Intel-gfx] [PATCH v3 1/3] drm/i915/display: ignore long HPDs based on a flag

[Vinod Govindapillai]

Some panels generate long HPD events even while connected to
the port. This cause some unexpected CI execution issues. A
new flag is added to track if such spurious long HPDs can be
ignored and are not processed further if the flag is set.

v2: Address patch styling comments (Jani Nikula)

v3: Ignoring the HPD moved to hotplug handler and now applies
    to all types of outputs (Imre Deak)

Signed-off-by: Vinod Govindapillai <vinod.govindapillai at intel.com>
---
 drivers/gpu/drm/i915/display/intel_display_core.h | 11 +++++++++++
 drivers/gpu/drm/i915/display/intel_hotplug.c      |  7 +++++++
 2 files changed, 18 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_display_core.h b/drivers/gpu/drm/i915/display/intel_display_core.h
index fb8670aa2932..251f774bd590 100644
--- a/drivers/gpu/drm/i915/display/intel_display_core.h
+++ b/drivers/gpu/drm/i915/display/intel_display_core.h
@@ -182,6 +182,17 @@ struct intel_hotplug {
 	 * blocked behind the non-DP one.
 	 */
 	struct workqueue_struct *dp_wq;
+
+	/*
+	 * Flag to track if long HPDs need not to be processed
+	 *
+	 * Some panels generate long HPDs while keep connected to the port.
+	 * This can cause issues with CI tests results. In CI systems we
+	 * don't expect to disconnect the panels and could ignore the long
+	 * HPDs generated from the faulty panels. This flag can be used as
+	 * cue to ignore the long HPDs and can be set / unset using debugfs.
+	 */
+	bool ignore_long_hpd;
 };
 
 struct intel_vbt_data {
diff --git a/drivers/gpu/drm/i915/display/intel_hotplug.c b/drivers/gpu/drm/i915/display/intel_hotplug.c
index 907ab7526cb4..f0a2aa648bb8 100644
--- a/drivers/gpu/drm/i915/display/intel_hotplug.c
+++ b/drivers/gpu/drm/i915/display/intel_hotplug.c
@@ -389,6 +389,13 @@ static void i915_hotplug_work_func(struct work_struct *work)
 
 	spin_unlock_irq(&dev_priv->irq_lock);
 
+	/* Skip calling encode hotplug handlers if ignore long HPD set*/
+	if (dev_priv->display.hotplug.ignore_long_hpd) {
+		drm_dbg_kms(&dev_priv->drm, "Ignore HPD flag on - skip encoder hotplug handlers\n");
+		mutex_unlock(&dev_priv->drm.mode_config.mutex);
+		return;
+	}
+
 	drm_connector_list_iter_begin(&dev_priv->drm, &conn_iter);
 	for_each_intel_connector_iter(connector, &conn_iter) {
 		enum hpd_pin pin;
-- 
2.34.1