[PATCH 1/3] drm/i915: Suppress spurious CPU FIFO underruns on ILK-IVB

ville.syrjala
2015-11-20T20:09:38Z

From: Ville Syrjälä <ville.syrjala@linux.intel.com>

We still get spurious pipe underruns on ILK/SNB/IVB under two
circumstances when dealing with PCH ports:
* When the pipe has been disabled, but FDI RX/TX is still enabled
* During FDI link training

Both cases seem to happen at least when we do VGA+HDMI cloning
from the same pipe. I don't think I've seen them when not cloning,
but can't be 100% sure.

Disable underrun reporting around those places to eliminate the
dmesg errors.

Testcase: igt/kms_setmode/basic-clone-single-crtc
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
drivers/gpu/drm/i915/intel_display.c | 20 +++++++++++++++++++-
1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 68fb449ded77..8a8104b7947d 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -4137,6 +4137,12 @@ 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);

@@ -4170,6 +4176,8 @@ 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 =
@@ -5062,12 +5070,22 @@ 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)
--
2.4.10