[PATCH 1/1 REPOST] drm: fix colour banding on Lenovo Thinkpad L540 panel

[Francesco P. Lovergine]

Hi,

there is an issue with Lenovo Thinkpad L540 panel i.e. a bad looking 
color banding with dark colors mainly, very similar to that present
in other models as pointed in referenced bugs.
That happens with any kernel starting from 4.8 up to the current.

Bug: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1749420
Bug: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1788308
Reviewed-by: Alex Deucher <alexdeucher at gmail.com> 
Signed-off-by: Francesco Paolo Lovergine <frankie at debian.org>
---
  drivers/gpu/drm/drm_edid.c | 3 +++
  1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 6325877c5fd6..48e06cc33e4d 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -141,6 +141,9 @@ static const struct edid_quirk {
  	/* LGD panel of HP zBook 17 G2, eDP 10 bpc, but reports unknown bpc */
  	{ "LGD", 764, EDID_QUIRK_FORCE_10BPC },

+	/* LGD panel of Lenovo L540 reports 8 bpc, but is a 6 bpc panel */
+	{ "LGD", 0x038e, EDID_QUIRK_FORCE_6BPC },
+
  	/* LG Philips LCD LP154W01-A5 */
  	{ "LPL", 0, EDID_QUIRK_DETAILED_USE_MAXIMUM_SIZE },
  	{ "LPL", 0x2a00, EDID_QUIRK_DETAILED_USE_MAXIMUM_SIZE },
-- 
2.30.2

-- 
Francesco P. Lovergine