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

We get spurious PCH FIFO underruns if we enable the reporting too soon
after enabling the crtc. Move it to be the last step, after the encoder
enable. Additionally we need an extra vblank wait, otherwise we still
get the underruns. Presumably the pipe/fdi isn't yet fully up and running
otherwise.

For symmetry, disable the PCH underrun reporting as the first thing,
just before encoder disable, when shutting down the crtc.

v2: Do the PCH underrun enable unconditionally (Jani, Daniel)

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org> (v1)
Link: http://patchwork.freedesktop.org/patch/msgid/1446225627-10809-1-git-send-email-ville.syrjala@linux.intel.com

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index a2d5938a9367f49acf200d36766c0672c99e5795..c0b6a2428048f0bf024f76b2fb6051af4f8aa300 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -4840,7 +4840,6 @@ static void ironlake_crtc_enable(struct drm_crtc *crtc)
        intel_crtc->active = true;
 
        intel_set_cpu_fifo_underrun_reporting(dev_priv, pipe, true);
-       intel_set_pch_fifo_underrun_reporting(dev_priv, pipe, true);
 
        for_each_encoder_on_crtc(dev, crtc, encoder)
                if (encoder->pre_enable)
@@ -4878,6 +4877,11 @@ static void ironlake_crtc_enable(struct drm_crtc *crtc)
 
        if (HAS_PCH_CPT(dev))
                cpt_verify_modeset(dev, intel_crtc->pipe);
+
+       /* 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_pch_fifo_underrun_reporting(dev_priv, pipe, true);
 }
 
 /* IPS only exists on ULT machines and is tied to pipe A. */
@@ -5006,15 +5010,15 @@ static void ironlake_crtc_disable(struct drm_crtc *crtc)
        int pipe = intel_crtc->pipe;
        u32 reg, temp;
 
+       if (intel_crtc->config->has_pch_encoder)
+               intel_set_pch_fifo_underrun_reporting(dev_priv, pipe, false);
+
        for_each_encoder_on_crtc(dev, crtc, encoder)
                encoder->disable(encoder);
 
        drm_crtc_vblank_off(crtc);
        assert_vblank_disabled(crtc);
 
-       if (intel_crtc->config->has_pch_encoder)
-               intel_set_pch_fifo_underrun_reporting(dev_priv, pipe, false);
-
        intel_disable_pipe(intel_crtc);
 
        ironlake_pfit_disable(intel_crtc, false);