drm/i915: Disable PSR when a PSR aux error happen

While PSR is active hardware will do aux transactions by it self to
wakeup sink to receive a new frame when necessary. If that
transaction is not acked by sink, hardware will trigger this
interruption.

So let's disable PSR as it is a hint that there is problem with this
sink.

The removed FIXME was asking to manually train the link but we don't
need to do that as by spec sink should do a short pulse when it is
out of sync with source, we just need to make sure it is awaken and
the SDP header with PSR inactive set it will trigger the short pulse
with a error set in the link status.

v3: added workarround to fix scheduled work starvation cause by
to frequent PSR error interruption

v4: only setting irq_aux_error as we don't care in clear it and
not using dev_priv->irq_lock as consequence.

v5: rebased: using edp_psr_shift()

Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181121225441.18785-4-jose.souza@intel.com

drivers/gpu/drm/i915/i915_drv.h

@@ -505,6 +505,7 @@ struct i915_psr {
 	ktime_t last_entry_attempt;
 	ktime_t last_exit;
 	bool sink_not_reliable;
+	bool irq_aux_error;
 };
 
 enum intel_pch {

drivers/gpu/drm/i915/intel_psr.c

@@ -169,6 +169,7 @@ void intel_psr_irq_handler(struct drm_i915_private *dev_priv, u32 psr_iir)
 	u32 transcoders = BIT(TRANSCODER_EDP);
 	enum transcoder cpu_transcoder;
 	ktime_t time_ns =  ktime_get();
+	u32 mask = 0;
 
 	if (INTEL_GEN(dev_priv) >= 8)
 		transcoders |= BIT(TRANSCODER_A) |
@@ -178,11 +179,23 @@ void intel_psr_irq_handler(struct drm_i915_private *dev_priv, u32 psr_iir)
 	for_each_cpu_transcoder_masked(dev_priv, cpu_transcoder, transcoders) {
 		int shift = edp_psr_shift(cpu_transcoder);
 
-		/* FIXME: Exit PSR and link train manually when this happens. */
-		if (psr_iir & EDP_PSR_ERROR(shift))
-			DRM_DEBUG_KMS("[transcoder %s] PSR aux error\n",
+		if (psr_iir & EDP_PSR_ERROR(shift)) {
+			DRM_WARN("[transcoder %s] PSR aux error\n",
 				 transcoder_name(cpu_transcoder));
 
+			dev_priv->psr.irq_aux_error = true;
+
+			/*
+			 * If this interruption is not masked it will keep
+			 * interrupting so fast that it prevents the scheduled
+			 * work to run.
+			 * Also after a PSR error, we don't want to arm PSR
+			 * again so we don't care about unmask the interruption
+			 * or unset irq_aux_error.
+			 */
+			mask |= EDP_PSR_ERROR(shift);
+		}
+
 		if (psr_iir & EDP_PSR_PRE_ENTRY(shift)) {
 			dev_priv->psr.last_entry_attempt = time_ns;
 			DRM_DEBUG_KMS("[transcoder %s] PSR entry attempt in 2 vblanks\n",
@@ -203,6 +216,13 @@ void intel_psr_irq_handler(struct drm_i915_private *dev_priv, u32 psr_iir)
 			}
 		}
 	}
+
+	if (mask) {
+		mask |= I915_READ(EDP_PSR_IMR);
+		I915_WRITE(EDP_PSR_IMR, mask);
+
+		schedule_work(&dev_priv->psr.work);
+	}
 }
 
 static bool intel_dp_get_colorimetry_status(struct intel_dp *intel_dp)
@@ -938,6 +958,16 @@ int intel_psr_set_debugfs_mode(struct drm_i915_private *dev_priv,
 	return ret;
 }
 
+static void intel_psr_handle_irq(struct drm_i915_private *dev_priv)
+{
+	struct i915_psr *psr = &dev_priv->psr;
+
+	intel_psr_disable_locked(psr->dp);
+	psr->sink_not_reliable = true;
+	/* let's make sure that sink is awaken */
+	drm_dp_dpcd_writeb(&psr->dp->aux, DP_SET_POWER, DP_SET_POWER_D0);
+}
+
 static void intel_psr_work(struct work_struct *work)
 {
 	struct drm_i915_private *dev_priv =
@@ -948,6 +978,9 @@ static void intel_psr_work(struct work_struct *work)
 	if (!dev_priv->psr.enabled)
 		goto unlock;
 
+	if (READ_ONCE(dev_priv->psr.irq_aux_error))
+		intel_psr_handle_irq(dev_priv);
+
 	/*
 	 * We have to make sure PSR is ready for re-enable
 	 * otherwise it keeps disabled until next full enable/disable cycle.