[PATCH 1/1] drm: This patch fixes colour banding caused by wrong information passed by the Lenovo Thinkpad L540 panel.

[PATCH 1/1] drm: This patch fixes colour banding caused by wrong information passed by the Lenovo Thinkpad L540 panel.

[Francesco Paolo Lovergine]

Hi, 

there is an issue with Lenovo Thinkpad L540 very similar to those described here:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1749420 or here:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1788308
that is a bad looking color banding with dark colors mainly.
It happens with any kernel starting from 4.8 up to the current.

Signed-off-by: Francesco Paolo Lovergine <frankie@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

Re: [PATCH 1/1] drm: This patch fixes colour banding caused by wrong information passed by the Lenovo Thinkpad L540 panel.

[Alex Deucher]

On Thu, Sep 23, 2021 at 2:15 PM Francesco Paolo Lovergine
<frankie@debian.org> wrote:
>
> Hi,

The patch title is a little long.  How about something like:

drm: fix colour banding on Lenovo Thinkpad L540 panel

>
> there is an issue with Lenovo Thinkpad L540 very similar to those described here:
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1749420 or here:
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1788308
> that is a bad looking color banding with dark colors mainly.
> It happens with any kernel starting from 4.8 up to the current.

Bugs should be referenced like:
Bug: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1749420
Bug: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1788308

Otherwise looks good to me.

Alex

>
> Signed-off-by: Francesco Paolo Lovergine <frankie@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

[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@gmail.com> 
Signed-off-by: Francesco Paolo Lovergine <frankie@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