drm/i915: Don't mark PCH underrun reporting as disabled for transcoder B/C on LPT-H

vsyrjala · vsyrjala · commit a168f5b3f179 · 2016-08-05T20:00:17.000+03:00
Marking PCH transcoder FIFO underrun reporting as disabled for transcoder B/C on LPT-H will block us from enabling the south error interrupt. So let's only mark transcoder A underrun reporting as disabled initially. This is a little tricky to hit since you need a machine with LPT-H, and the BIOS must enable either pipe B or C at boot. Then i915 would mark the "transcoder B/C" underrun reporting as disabled and never enable it again, meaning south interrupts would never get enabled either. The only other interrupt in there is actually the poison interrupt which, if we could ever trigger it, would just result in a little error in dmesg. Here's the resulting change in SDEIMR on my HSW when I boot it with multiple displays attached: - (0x000c4004): 0xf115ffff + (0x000c4004): 0xf114ffff My previous attempt [1] tried to fix this a little differently, but Daniel requested I do this instead. [1] https://lists.freedesktop.org/archives/intel-gfx/2015-November/081420.html Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Link: http://patchwork.freedesktop.org/patch/msgid/1470416417-15021-1-git-send-email-ville.syrjala@linux.intel.com Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
@@ -15771,6 +15771,13 @@ static bool intel_encoder_has_connectors(struct intel_encoder *encoder)
 	return false;
 }
 
+static bool has_pch_trancoder(struct drm_i915_private *dev_priv,
+			      enum transcoder pch_transcoder)
+{
+	return HAS_PCH_IBX(dev_priv) || HAS_PCH_CPT(dev_priv) ||
+		(HAS_PCH_LPT_H(dev_priv) && pch_transcoder == TRANSCODER_A);
+}
+
 static void intel_sanitize_crtc(struct intel_crtc *crtc)
 {
 	struct drm_device *dev = crtc->base.dev;
@@ -15849,7 +15856,17 @@ static void intel_sanitize_crtc(struct intel_crtc *crtc)
 		 * worst a fifo underrun happens which also sets this to false.
 		 */
 		crtc->cpu_fifo_underrun_disabled = true;
-		crtc->pch_fifo_underrun_disabled = true;
+		/*
+		 * We track the PCH trancoder underrun reporting state
+		 * within the crtc. With crtc for pipe A housing the underrun
+		 * reporting state for PCH transcoder A, crtc for pipe B housing
+		 * it for PCH transcoder B, etc. LPT-H has only PCH transcoder A,
+		 * and marking underrun reporting as disabled for the non-existing
+		 * PCH transcoders B and C would prevent enabling the south
+		 * error interrupt (see cpt_can_enable_serr_int()).
+		 */
+		if (has_pch_trancoder(dev_priv, (enum transcoder)crtc->pipe))
+			crtc->pch_fifo_underrun_disabled = true;
 	}
 }
 
