Attached is the difference between kernel 4.7 and 4.8 in the Intel
graphics driver. It's still a big diff, but at least eliminates my above
theories about the cause of the regression. Now the main suspect, I
think, would be:
@@ -12095,21 +12181,11 @@ connected_sink_compute_bpp(struct intel_connector
*connector,
pipe_config->pipe_bpp = connector->base.display_info.bpc*3;
}
- /* Clamp bpp to default limit on screens without EDID 1.4 */
- if (connector->base.display_info.bpc == 0) {
- int type = connector->base.connector_type;
- int clamp_bpp = 24;
-
- /* Fall back to 18 bpp when DP sink capability is unknown. */
- if (type == DRM_MODE_CONNECTOR_DisplayPort ||
- type == DRM_MODE_CONNECTOR_eDP)
- clamp_bpp = 18;
-
- if (bpp > clamp_bpp) {
- DRM_DEBUG_KMS("clamping display bpp (was %d) to default
limit of %d\n",
- bpp, clamp_bpp);
- pipe_config->pipe_bpp = clamp_bpp;
- }
+ /* Clamp bpp to 8 on screens without EDID 1.4 */
+ if (connector->base.display_info.bpc == 0 && bpp > 24) {
+ DRM_DEBUG_KMS("clamping display bpp (was %d) to default limit
of 24\n",
+ bpp);
+ pipe_config->pipe_bpp = 24;
}
}
** Patch added: "i915_changes_v4.7-v4.8.diff.gz"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1749420/+attachment/5056341/+files/i915_changes_v4.7-v4.8.diff.gz
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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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