From: Swati Sharma <swati2.sha...@intel.com>

In this patch enables support for detecting link failures between
PCON and HDMI sink in i915 driver. HDMI link loss indication to
upstream DP source is indicated via IRQ_HPD. This is followed by
reading of HDMI link configuration status (HDMI_TX_LINK_ACTIVE_STATUS).
If the PCON → HDMI 2.1 link status is off; reinitiate frl link
training to recover. Also, report HDMI FRL link error count range for
each individual FRL active lane is indicated by
DOWNSTREAM_HDMI_ERROR_STATUS_LN registers.

v2: Checked for dpcd read and write failures and added debug message.
(Uma Shankar)

v3: Rearranged code to re-start FRL link training or fall back to
TMDS mode.

v4: Resused function to check frl which inturn restarts FRL and
fallback to TMDS mode.

Signed-off-by: Swati Sharma <swati2.sha...@intel.com>
Signed-off-by: Ankit Nautiyal <ankit.k.nauti...@intel.com>
Reviewed-by: Uma Shankar <uma.shan...@intel.com> (v2)
---
 drivers/gpu/drm/i915/display/intel_dp.c | 53 +++++++++++++++++++++++--
 1 file changed, 50 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c 
b/drivers/gpu/drm/i915/display/intel_dp.c
index 9d0adce14613..daf2faaa40fb 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -6005,6 +6005,28 @@ intel_dp_check_mst_status(struct intel_dp *intel_dp)
        return link_ok;
 }
 
+static void
+intel_dp_handle_hdmi_link_status_change(struct intel_dp *intel_dp)
+{
+       bool is_active;
+       u8 buf = 0;
+
+       is_active = drm_dp_pcon_hdmi_link_active(&intel_dp->aux);
+       if (intel_dp->frl.is_trained && !is_active) {
+               if (drm_dp_dpcd_readb(&intel_dp->aux, 
DP_PCON_HDMI_LINK_CONFIG_1, &buf) < 0)
+                       return;
+
+               buf &=  ~DP_PCON_ENABLE_HDMI_LINK;
+               if (drm_dp_dpcd_writeb(&intel_dp->aux, 
DP_PCON_HDMI_LINK_CONFIG_1, buf) < 0)
+                       return;
+
+               drm_dp_pcon_hdmi_frl_link_error_count(&intel_dp->aux, 
&intel_dp->attached_connector->base);
+
+               /* Restart FRL training or fall back to TMDS mode */
+               intel_dp_check_frl_training(intel_dp);
+       }
+}
+
 static bool
 intel_dp_needs_link_retrain(struct intel_dp *intel_dp)
 {
@@ -6370,7 +6392,7 @@ intel_dp_hotplug(struct intel_encoder *encoder,
        return state;
 }
 
-static void intel_dp_check_service_irq(struct intel_dp *intel_dp)
+static void intel_dp_check_device_service_irq(struct intel_dp *intel_dp)
 {
        struct drm_i915_private *i915 = dp_to_i915(intel_dp);
        u8 val;
@@ -6394,6 +6416,30 @@ static void intel_dp_check_service_irq(struct intel_dp 
*intel_dp)
                drm_dbg_kms(&i915->drm, "Sink specific irq unhandled\n");
 }
 
+static void intel_dp_check_link_service_irq(struct intel_dp *intel_dp)
+{
+       struct drm_i915_private *i915 = dp_to_i915(intel_dp);
+       u8 val;
+
+       if (intel_dp->dpcd[DP_DPCD_REV] < 0x11)
+               return;
+
+       if (drm_dp_dpcd_readb(&intel_dp->aux,
+                             DP_LINK_SERVICE_IRQ_VECTOR_ESI0, &val) != 1 || 
!val) {
+               drm_dbg_kms(&i915->drm, "Error in reading link service irq 
vector\n");
+               return;
+       }
+
+       if (drm_dp_dpcd_writeb(&intel_dp->aux,
+                              DP_LINK_SERVICE_IRQ_VECTOR_ESI0, val) != 1) {
+               drm_dbg_kms(&i915->drm, "Error in writing link service irq 
vector\n");
+               return;
+       }
+
+       if (val & HDMI_LINK_STATUS_CHANGED)
+               intel_dp_handle_hdmi_link_status_change(intel_dp);
+}
+
 /*
  * According to DP spec
  * 5.1.2:
@@ -6433,7 +6479,8 @@ intel_dp_short_pulse(struct intel_dp *intel_dp)
                return false;
        }
 
-       intel_dp_check_service_irq(intel_dp);
+       intel_dp_check_device_service_irq(intel_dp);
+       intel_dp_check_link_service_irq(intel_dp);
 
        /* Handle CEC interrupts, if any */
        drm_dp_cec_irq(&intel_dp->aux);
@@ -6863,7 +6910,7 @@ intel_dp_detect(struct drm_connector *connector,
            to_intel_connector(connector)->detect_edid)
                status = connector_status_connected;
 
-       intel_dp_check_service_irq(intel_dp);
+       intel_dp_check_device_service_irq(intel_dp);
 
 out:
        if (status != connector_status_connected && !intel_dp->is_mst)
-- 
2.17.1

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