drm/i915: Try to shut up more ILK underruns

Take a bigger hammer to the underrun suppression on ILK. Instead of
trying to suppress them at specific points in the modeset sequence just
silence them across the entire sequence. This gets rid of some underruns
at least on my ILK. Note that this changes SNB and IVB to follow the
same approach just to keep the code less convoluted. The difference is
that on those platforms we won't suppress CPU underruns for port A since
it doesn't seem to be necessary.

My ILK has port A eDP and two PCH HDMI ports, so I can't be sure this is
as effective on other PCH port types. Perhaps we still need some of
Daniel's extra vblank waits [2]?

I've still been able to trigger an underrun on the other pipe, but
fixing that perhaps needs the LP1+ disable trick I implemented here [1]
which never got merged.

A few details which hamper stress testing on my ILK are that sometimes
the PCH transcoder gets messed up and refuses to shut down, and sometimes
even the panel power sequencer apparently gets stuck on the always on
position.

[1] https://lists.freedesktop.org/archives/intel-gfx/2014-March/041317.html
[2] https://lists.freedesktop.org/archives/intel-gfx/2016-January/086397.html

v2: Add a note that we also get underruns when enabling PCH ports

Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> (v1)
Link: http://patchwork.freedesktop.org/patch/msgid/1459536799-18109-2-git-send-email-ville.syrjala@linux.intel.com
Reviewed-by: Patrik Jakobsson <patrik.jakobsson@linux.intel.com>

1 files changed, 23 insertions, 22 deletions

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 551541b3038c..bf9e3474222d 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -4088,12 +4088,6 @@ static void ironlake_pch_enable(struct drm_crtc *crtc)
 	I915_WRITE(FDI_RX_TUSIZE1(pipe),
 		   I915_READ(PIPE_DATA_M1(pipe)) & TU_SIZE_MASK);
 
-	/*
-	 * Sometimes spurious CPU pipe underruns happen during FDI
-	 * training, at least with VGA+HDMI cloning. Suppress them.
-	 */
-	intel_set_cpu_fifo_underrun_reporting(dev_priv, pipe, false);
-
 	/* For PCH output, training FDI link */
 	dev_priv->display.fdi_link_train(crtc);
 
@@ -4128,8 +4122,6 @@ static void ironlake_pch_enable(struct drm_crtc *crtc)
 
 	intel_fdi_normal_train(crtc);
 
-	intel_set_cpu_fifo_underrun_reporting(dev_priv, pipe, true);
-
 	/* For PCH DP, enable TRANS_DP_CTL */
 	if (HAS_PCH_CPT(dev) && intel_crtc->config->has_dp_encoder) {
 		const struct drm_display_mode *adjusted_mode =
@@ -4732,6 +4724,18 @@ static void ironlake_crtc_enable(struct drm_crtc *crtc)
 	if (WARN_ON(intel_crtc->active))
 		return;
 
+	/*
+	 * Sometimes spurious CPU pipe underruns happen during FDI
+	 * training, at least with VGA+HDMI cloning. Suppress them.
+	 *
+	 * On ILK we get an occasional spurious CPU pipe underruns
+	 * between eDP port A enable and vdd enable. Also PCH port
+	 * enable seems to result in the occasional CPU pipe underrun.
+	 *
+	 * Spurious PCH underruns also occur during PCH enabling.
+	 */
+	if (intel_crtc->config->has_pch_encoder || IS_GEN5(dev_priv))
+		intel_set_cpu_fifo_underrun_reporting(dev_priv, pipe, false);
 	if (intel_crtc->config->has_pch_encoder)
 		intel_set_pch_fifo_underrun_reporting(dev_priv, pipe, false);
 
@@ -4753,8 +4757,6 @@ static void ironlake_crtc_enable(struct drm_crtc *crtc)
 
 	intel_crtc->active = true;
 
-	intel_set_cpu_fifo_underrun_reporting(dev_priv, pipe, true);
-
 	for_each_encoder_on_crtc(dev, crtc, encoder)
 		if (encoder->pre_enable)
 			encoder->pre_enable(encoder);
@@ -4796,6 +4798,7 @@ static void ironlake_crtc_enable(struct drm_crtc *crtc)
 	/* Must wait for vblank to avoid spurious PCH FIFO underruns */
 	if (intel_crtc->config->has_pch_encoder)
 		intel_wait_for_vblank(dev, pipe);
+	intel_set_cpu_fifo_underrun_reporting(dev_priv, pipe, true);
 	intel_set_pch_fifo_underrun_reporting(dev_priv, pipe, true);
 }
 
@@ -4948,8 +4951,15 @@ static void ironlake_crtc_disable(struct drm_crtc *crtc)
 	struct intel_encoder *encoder;
 	int pipe = intel_crtc->pipe;
 
-	if (intel_crtc->config->has_pch_encoder)
+	/*
+	 * Sometimes spurious CPU pipe underruns happen when the
+	 * pipe is already disabled, but FDI RX/TX is still enabled.
+	 * Happens at least with VGA+HDMI cloning. Suppress them.
+	 */
+	if (intel_crtc->config->has_pch_encoder) {
+		intel_set_cpu_fifo_underrun_reporting(dev_priv, pipe, false);
 		intel_set_pch_fifo_underrun_reporting(dev_priv, pipe, false);
+	}
 
 	for_each_encoder_on_crtc(dev, crtc, encoder)
 		encoder->disable(encoder);
@@ -4957,22 +4967,12 @@ static void ironlake_crtc_disable(struct drm_crtc *crtc)
 	drm_crtc_vblank_off(crtc);
 	assert_vblank_disabled(crtc);
 
-	/*
-	 * Sometimes spurious CPU pipe underruns happen when the
-	 * pipe is already disabled, but FDI RX/TX is still enabled.
-	 * Happens at least with VGA+HDMI cloning. Suppress them.
-	 */
-	if (intel_crtc->config->has_pch_encoder)
-		intel_set_cpu_fifo_underrun_reporting(dev_priv, pipe, false);
-
 	intel_disable_pipe(intel_crtc);
 
 	ironlake_pfit_disable(intel_crtc, false);
 
-	if (intel_crtc->config->has_pch_encoder) {
+	if (intel_crtc->config->has_pch_encoder)
 		ironlake_fdi_disable(crtc);
-		intel_set_cpu_fifo_underrun_reporting(dev_priv, pipe, true);
-	}
 
 	for_each_encoder_on_crtc(dev, crtc, encoder)
 		if (encoder->post_disable)
@@ -5002,6 +5002,7 @@ static void ironlake_crtc_disable(struct drm_crtc *crtc)
 		ironlake_fdi_pll_disable(intel_crtc);
 	}
 
+	intel_set_cpu_fifo_underrun_reporting(dev_priv, pipe, true);
 	intel_set_pch_fifo_underrun_reporting(dev_priv, pipe, true);
 }