Wait a minute... it sounds like dithering is always going to be disabled
(since commit 611032bfa71a7) for the case of (pipe_config->pipe_bpp ==
6*3).
index 5a9da484bb23..ef65b4be5e56 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -13060,8 +13060,11 @@ intel_modeset_pipe_config(struct drm_crtc *crtc,
}
/* Dithering seems to not pass-through bits correctly when it should, so
- * only enable it on 6bpc panels. */
- pipe_config->dither = pipe_config->pipe_bpp == 6*3;
+ * only enable it on 6bpc panels and when its not a compliance
+ * test requesting 6bpc video pattern.
+ */
+ pipe_config->dither = (pipe_config->pipe_bpp == 6*3) &&
+ !pipe_config->dither_force_disable;
DRM_DEBUG_KMS("hw max bpp: %i, pipe bpp: %i, dithering: %i\n",
base_bpp, pipe_config->pipe_bpp, pipe_config->dither);
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index e245802c5727..0fafbec6dacf 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -28,8 +28,10 @@
#include <linux/i2c.h>
#include <linux/slab.h>
#include <linux/export.h>
+#include <linux/types.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
+#include <asm/byteorder.h>
#include <drm/drmP.h>
#include <drm/drm_atomic_helper.h>
#include <drm/drm_crtc.h>
@@ -1593,6 +1595,13 @@ static int intel_dp_compute_bpp(struct intel_dp
*intel_dp,
if (bpc > 0)
bpp = min(bpp, 3*bpc);
+ /* For DP Compliance we override the computed bpp for the pipe */
+ if (intel_dp->compliance.test_data.bpc != 0) {
+ pipe_config->pipe_bpp = 3*intel_dp->compliance.test_data.bpc;
+ pipe_config->dither_force_disable = pipe_config->pipe_bpp ==
6*3;
+ DRM_DEBUG_KMS("Setting pipe_bpp to %d\n",
+ pipe_config->pipe_bpp);
+ }
return bpp;
}
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https://bugs.launchpad.net/bugs/1749420
Title:
Colour banding and artefacts appear system-wide on an Asus Zenbook
UX303LA with Intel HD 4400 graphics
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