Re: [PATCH v3 0/2] drm: minimum backlight overrides and implementation for amdgpu

[Jani Nikula]

On Wed, 31 Jul 2024, Thomas Weißschuh <linux@xxxxxxxxxxxxxx> wrote:
> The value of "min_input_signal" returned from ATIF on a Framework AMD 13
> is "12". This leads to a fairly bright minimum display backlight.
>
> Add a generic override helper for the user to override the settings
> provided by the firmware through the kernel cmdline.
> Also add amdgpu as a user of that helper.
>
> One solution would be a fixed firmware version, which was announced but
> has no timeline.

The flip side is that if we add this now, it pretty much has a timeline:
We'll have to carry and support it forever.

It's not a great prospect for something so specific. Not to mention that
the limits are generally there for electrical minimums that should not
be overridden. And before you know it, we'll have bug reports about
flickering screens...

BR,
Jani.


>
> This helper does conflict with the mode override via the cmdline.
> Only one can be specified.
> IMO the mode override can be extended to also handle "min-brightness"
> when that becomes necessary.
>
> ---
> Changes in v3:
> - Switch to cmdline override parameter
> - Link to v2: https://lore.kernel.org/r/20240623-amdgpu-min-backlight-quirk-v2-0-cecf7f49da9b@xxxxxxxxxxxxxx
>
> Changes in v2:
> - Introduce proper drm backlight quirk infrastructure
> - Quirk by EDID and DMI instead of only DMI
> - Limit quirk to only single Framework 13 matte panel
> - Link to v1: https://lore.kernel.org/r/20240610-amdgpu-min-backlight-quirk-v1-1-8459895a5b2a@xxxxxxxxxxxxxx
>
> ---
> Thomas Weißschuh (2):
>       drm/connector: add drm_connector_get_cmdline_min_brightness_override()
>       drm/amd/display: implement minimum brightness override
>
>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |  6 ++++
>  drivers/gpu/drm/drm_connector.c                   | 34 +++++++++++++++++++++++
>  include/drm/drm_connector.h                       |  2 ++
>  3 files changed, 42 insertions(+)
> ---
> base-commit: 36821612eb3091a21f7f4a907b497064725080c3
> change-id: 20240610-amdgpu-min-backlight-quirk-8402fd8e736a
>
> Best regards,

-- 
Jani Nikula, Intel