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drm/i915/dp: Revert "drm/i915/dp: fall back to 18 bpp when sink capability is unknown"

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This reverts commit 013dd9e03872
("drm/i915/dp: fall back to 18 bpp when sink capability is unknown")

This commit introduced a regression into stable kernels,
as it reduces output color depth to 6 bpc for any video
sink connected to a Displayport connector if that sink
doesn't report a specific color depth via EDID, or if
our EDID parser doesn't actually recognize the proper
bpc from EDID.

Affected are active DisplayPort->VGA converters and
active DisplayPort->DVI converters. Both should be
able to handle 8 bpc, but are degraded to 6 bpc with
this patch.

The reverted commit was meant to fix
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=105331

A followup patch implements a fix for that specific bug,
which is caused by a faulty EDID of the affected DP panel
by adding a new EDID quirk for that panel.

DP 18 bpp fallback handling and other improvements to
DP sink bpc detection will be handled for future
kernels in a separate series of patches.

Please backport to stable.

Signed-off-by: Mario Kleiner <mario.kleiner.de@gmail.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Cc: stable@vger.kernel.org
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>
This commit is contained in:
Mario Kleiner 2016-07-06 12:05:45 +02:00 committed by Dave Airlie
parent e10aec652f
commit 196f954e25
1 changed files with 5 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
drivers/gpu/drm/i915/intel_display.c
View File

@ -12106,21 +12106,11 @@ 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;
}
}