drm/i915/display/psr: Lock and unlock PSR around pipe updates

Frontbuffer rendering and page flips can race with each other
and this can potentialy cause issues with PSR2 selective fetch.

And because pipe/crtc updates are time sentive we can't grab the
PSR lock after intel_pipe_update_start() and before
intel_pipe_update_end().

So here adding the lock and unlock functions and calls, the
proper PSR2 selective fetch handling will come in a separated patch.

v2:
- fixed new functions documentation
Reviewed-by: Jouni Högander <jouni.hogander@intel.com>
Cc: Jouni Högander <jouni.hogander@intel.com>
Cc: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220405155344.47219-2-jose.souza@intel.com

drivers/gpu/drm/i915/display/intel_crtc.c

@@ -507,6 +507,8 @@ void intel_pipe_update_start(struct intel_crtc_state *new_crtc_state)
 						      VBLANK_EVASION_TIME_US);
 	max = vblank_start - 1;
 
+	intel_psr_lock(new_crtc_state);
+
 	if (min <= 0 || max <= 0)
 		goto irq_disable;
 
@@ -518,7 +520,7 @@ void intel_pipe_update_start(struct intel_crtc_state *new_crtc_state)
 	 * VBL interrupts will start the PSR exit and prevent a PSR
 	 * re-entry as well.
 	 */
-	intel_psr_wait_for_idle(new_crtc_state);
+	intel_psr_wait_for_idle_locked(new_crtc_state);
 
 	local_irq_disable();
 
@@ -683,6 +685,8 @@ void intel_pipe_update_end(struct intel_crtc_state *new_crtc_state)
 
 	local_irq_enable();
 
+	intel_psr_unlock(new_crtc_state);
+
 	if (intel_vgpu_active(dev_priv))
 		return;
 

drivers/gpu/drm/i915/display/intel_psr.c

@@ -1548,10 +1548,19 @@ void intel_psr2_program_plane_sel_fetch(struct intel_plane *plane,
 void intel_psr2_program_trans_man_trk_ctl(const struct intel_crtc_state *crtc_state)
 {
 	struct drm_i915_private *dev_priv = to_i915(crtc_state->uapi.crtc->dev);
+	struct intel_encoder *encoder;
 
 	if (!crtc_state->enable_psr2_sel_fetch)
 		return;
 
+	for_each_intel_encoder_mask_with_psr(&dev_priv->drm, encoder,
+					     crtc_state->uapi.encoder_mask) {
+		struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
+
+		lockdep_assert_held(&intel_dp->psr.lock);
+		break;
+	}
+
 	intel_de_write(dev_priv, PSR2_MAN_TRK_CTL(crtc_state->cpu_transcoder),
 		       crtc_state->psr2_man_track_ctl);
 }
@@ -1919,13 +1928,13 @@ static int _psr1_ready_for_pipe_update_locked(struct intel_dp *intel_dp)
 }
 
 /**
- * intel_psr_wait_for_idle - wait for PSR be ready for a pipe update
+ * intel_psr_wait_for_idle_locked - wait for PSR be ready for a pipe update
  * @new_crtc_state: new CRTC state
  *
  * This function is expected to be called from pipe_update_start() where it is
  * not expected to race with PSR enable or disable.
  */
-void intel_psr_wait_for_idle(const struct intel_crtc_state *new_crtc_state)
+void intel_psr_wait_for_idle_locked(const struct intel_crtc_state *new_crtc_state)
 {
 	struct drm_i915_private *dev_priv = to_i915(new_crtc_state->uapi.crtc->dev);
 	struct intel_encoder *encoder;
@@ -1938,12 +1947,10 @@ void intel_psr_wait_for_idle(const struct intel_crtc_state *new_crtc_state)
 		struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
 		int ret;
 
-		mutex_lock(&intel_dp->psr.lock);
+		lockdep_assert_held(&intel_dp->psr.lock);
 
-		if (!intel_dp->psr.enabled) {
-			mutex_unlock(&intel_dp->psr.lock);
+		if (!intel_dp->psr.enabled)
 			continue;
-		}
 
 		if (intel_dp->psr.psr2_enabled)
 			ret = _psr2_ready_for_pipe_update_locked(intel_dp);
@@ -1952,8 +1959,6 @@ void intel_psr_wait_for_idle(const struct intel_crtc_state *new_crtc_state)
 
 		if (ret)
 			drm_err(&dev_priv->drm, "PSR wait timed out, atomic update may fail\n");
-
-		mutex_unlock(&intel_dp->psr.lock);
 	}
 }
 
@@ -2444,3 +2449,51 @@ bool intel_psr_enabled(struct intel_dp *intel_dp)
 
 	return ret;
 }
+
+/**
+ * intel_psr_lock - grab PSR lock
+ * @crtc_state: the crtc state
+ *
+ * This is initially meant to be used by around CRTC update, when
+ * vblank sensitive registers are updated and we need grab the lock
+ * before it to avoid vblank evasion.
+ */
+void intel_psr_lock(const struct intel_crtc_state *crtc_state)
+{
+	struct drm_i915_private *i915 = to_i915(crtc_state->uapi.crtc->dev);
+	struct intel_encoder *encoder;
+
+	if (!crtc_state->has_psr)
+		return;
+
+	for_each_intel_encoder_mask_with_psr(&i915->drm, encoder,
+					     crtc_state->uapi.encoder_mask) {
+		struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
+
+		mutex_lock(&intel_dp->psr.lock);
+		break;
+	}
+}
+
+/**
+ * intel_psr_unlock - release PSR lock
+ * @crtc_state: the crtc state
+ *
+ * Release the PSR lock that was held during pipe update.
+ */
+void intel_psr_unlock(const struct intel_crtc_state *crtc_state)
+{
+	struct drm_i915_private *i915 = to_i915(crtc_state->uapi.crtc->dev);
+	struct intel_encoder *encoder;
+
+	if (!crtc_state->has_psr)
+		return;
+
+	for_each_intel_encoder_mask_with_psr(&i915->drm, encoder,
+					     crtc_state->uapi.encoder_mask) {
+		struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
+
+		mutex_unlock(&intel_dp->psr.lock);
+		break;
+	}
+}

drivers/gpu/drm/i915/display/intel_psr.h

@@ -41,7 +41,7 @@ void intel_psr_get_config(struct intel_encoder *encoder,
 			  struct intel_crtc_state *pipe_config);
 void intel_psr_irq_handler(struct intel_dp *intel_dp, u32 psr_iir);
 void intel_psr_short_pulse(struct intel_dp *intel_dp);
-void intel_psr_wait_for_idle(const struct intel_crtc_state *new_crtc_state);
+void intel_psr_wait_for_idle_locked(const struct intel_crtc_state *new_crtc_state);
 bool intel_psr_enabled(struct intel_dp *intel_dp);
 int intel_psr2_sel_fetch_update(struct intel_atomic_state *state,
 				struct intel_crtc *crtc);
@@ -55,4 +55,7 @@ void intel_psr2_disable_plane_sel_fetch(struct intel_plane *plane,
 void intel_psr_pause(struct intel_dp *intel_dp);
 void intel_psr_resume(struct intel_dp *intel_dp);
 
+void intel_psr_lock(const struct intel_crtc_state *crtc_state);
+void intel_psr_unlock(const struct intel_crtc_state *crtc_state);
+
 #endif /* __INTEL_PSR_H__ */