[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 at 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 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