drm/i915: fix fdi related fifo underruns on hsw

Similar to

commit 37ca8d4ccd9860df0747aa2ea281a3c9c4bf8826
Author: Ville Syrjälä <ville.syrjala@linux.intel.com>
Date:   Fri Oct 30 19:20:27 2015 +0200

    drm/i915: Enable PCH FIFO underruns later on ILK/SNB/IVB

we can only enable fifo underrun reporting when using the fdi/lpt
after everything is set up and after a bit of waiting. The waiting
is required, enabling it right after enabling encoders will first trigger
an underrun on the pch and then, 1 frame later, an underrun on the
cpu. Two vblank waits after encoder enabling seems enough to curb it.

And similar to

Author: Ville Syrjälä <ville.syrjala@linux.intel.com>
Date:   Fri Nov 20 22:09:18 2015 +0200

    drm/i915: Suppress spurious CPU FIFO underruns on ILK-IVB

we also need to make sure cpu fifo underrun reporting is disabled when
enabling the fdi rx/tx and pch transcoder&port. But somehow this is
only needed when enabling, not also when disabling.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1448705139-12534-1-git-send-email-daniel.vetter@ffwll.ch
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91578
Tested-by: Mika Kahola <mika.kahola@intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-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
index b95c325..b332326 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -4978,7 +4978,11 @@ static void haswell_crtc_enable(struct drm_crtc *crtc)
 
        intel_crtc->active = true;
 
-       intel_set_cpu_fifo_underrun_reporting(dev_priv, pipe, true);
+       if (intel_crtc->config->has_pch_encoder)
+               intel_set_cpu_fifo_underrun_reporting(dev_priv, pipe, false);
+       else
+               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);
@@ -5022,9 +5026,13 @@ static void haswell_crtc_enable(struct drm_crtc *crtc)
                intel_opregion_notify_encoder(encoder, true);
        }
 
-       if (intel_crtc->config->has_pch_encoder)
+       if (intel_crtc->config->has_pch_encoder) {
+               intel_wait_for_vblank(dev, pipe);
+               intel_wait_for_vblank(dev, pipe);
+               intel_set_cpu_fifo_underrun_reporting(dev_priv, pipe, true);
                intel_set_pch_fifo_underrun_reporting(dev_priv, TRANSCODER_A,
                                                      true);
+       }
 
        /* If we change the relative order between pipe/planes enabling, we need
         * to change the workaround. */