From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
When the video timings are suitably aligned so that all different
periods start at phase 0 (ie. none of the periods start mid-pixel)
we can inform the sink about this. Supposedly the sink can then
optimize certain things. Obviously this is only relevant when
outputting >8bpc data since otherwise there are no mid-pixel phases.
Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/intel_hdmi.c | 48 +++++++++++++++++++++++++++++++++++++++
1 file changed, 48 insertions(+)
diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
index bd09812..d268c1a 100644
--- a/drivers/gpu/drm/i915/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/intel_hdmi.c
@@ -493,6 +493,49 @@ static bool hdmi_sink_is_deep_color(struct drm_encoder *encoder)
return false;
}
+/*
+ * Determine if default_phase=1 can be indicated in the GCP infoframe.
+ *
+ * From HDMI specification 1.4a:
+ * - The first pixel of each Video Data Period shall always have a pixel packing phase of 0
+ * - The first pixel following each Video Data Period shall have a pixel packing phase of 0
+ * - The PP bits shall be constant for all GCPs and will be equal to the last packing phase
+ * - The first pixel following every transition of HSYNC or VSYNC shall have a pixel packing
+ * phase of 0
+ */
+static bool gcp_default_phase_possible(int pipe_bpp,
+ const struct drm_display_mode *mode)
+{
+ unsigned int pixels_per_group;
+
+ switch (pipe_bpp) {
+ case 30:
+ /* 4 pixels in 5 clocks */
+ pixels_per_group = 4;
+ break;
+ case 36:
+ /* 2 pixels in 3 clocks */
+ pixels_per_group = 2;
+ break;
+ case 48:
+ /* 1 pixel in 2 clocks */
+ pixels_per_group = 1;
+ break;
+ default:
+ /* phase information not relevant for 8bpc */
+ return false;
+ }
+
+ return mode->crtc_hdisplay % pixels_per_group == 0 &&
+ mode->crtc_htotal % pixels_per_group == 0 &&
+ mode->crtc_hblank_start % pixels_per_group == 0 &&
+ mode->crtc_hblank_end % pixels_per_group == 0 &&
+ mode->crtc_hsync_start % pixels_per_group == 0 &&
+ mode->crtc_hsync_end % pixels_per_group == 0 &&
+ ((mode->flags & DRM_MODE_FLAG_INTERLACE) == 0 ||
+ mode->crtc_htotal/2 % pixels_per_group == 0);
+}
+
static bool intel_set_gcp_infoframe(struct drm_encoder *encoder)
{
struct drm_i915_private *dev_priv = encoder->dev->dev_private;
@@ -512,6 +555,11 @@ static bool intel_set_gcp_infoframe(struct drm_encoder *encoder)
if (hdmi_sink_is_deep_color(encoder))
val |= GCP_COLOR_INDICATION;
+ /* Enable default_phase whenever the display mode is suitably aligned */
+ if (gcp_default_phase_possible(crtc->config.pipe_bpp,
+ &crtc->config.adjusted_mode))
+ val |= GCP_DEFAULT_PHASE_ENABLE;
+
I915_WRITE(reg, val);
return val != 0;
--
2.0.4
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