drm/i915: use pipe_config for lvds dithering
Up to now we've relied on the bios to get this right for us. Let's try
out whether our code has improved a bit, since we should dither
always when the output bpp doesn't match the plane bpp.
- gen5+ should be fine, since we only use the bios hint as an upgrade.
- gen4 changes, since here dithering is still controlled in the lvds
register.
- gen2/3 has implicit dithering depeding upon whether you use 2 or 3
lvds pairs (which makes sense, since it only supports 8bpc pipe
outpu configurations).
- hsw doesn't support lvds.
v2: Remove redudant dither setting.
v3: Completly drop reliance on dev_priv->lvds_dither.
v4: Enable dithering on gen2/3 only when we have a 18bpp panel, since
up-dithering to a 24bpp panel is not supported by the hw. Spotted by
Ville.
v5: Also only enable lvds port dithering on gen4 for 18bpp modes. In
practice this only excludes dithering a 10bpc plane down for a 24bpp
lvds panel. Not something we truly care about. Again noticed by Ville.
v6: Actually git add.
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 3595c82..a5fe976 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -213,6 +213,11 @@
/* DP has a bunch of special case unfortunately, so mark the pipe
* accordingly. */
bool has_dp_encoder;
+
+ /*
+ * Enable dithering, used when the selected pipe bpp doesn't match the
+ * plane bpp.
+ */
bool dither;
/* Controls for the clock computation, to override various stages. */