[PATCH v4 0/3] drm: Minimum backlight overrides and implementation for amdgpu

[Thomas Weißschuh]

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.

Introduce a quirk to override "min_input_signal" to "0" which leads to a
much lower minimum brightness, which is still readable even in daylight.

Tested on a Framework AMD 13 BIOS 3.05 and Framework AMD 16.

One solution would be a fixed firmware version, which was announced but
has no timeline.

---
Changes in v4:
- Switch back to v2 implementation
- Add MODULE_DESCRIPTION()
- Simplify quirk infrastructure to only handle min backlight quirks.
  It can be extended if necessary.
- Expand documentation.
- Link to v3: https://lore.kernel.org/r/20240731-amdgpu-min-backlight-quirk-v3-0-46d40bb21a62@weissschuh.net

Changes in v3:
- Switch to cmdline override parameter
- Link to v2: https://lore.kernel.org/r/20240623-amdgpu-min-backlight-quirk-v2-0-cecf7f49da9b@weissschuh.net

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@weissschuh.net

---
Thomas Weißschuh (3):
      drm: Add panel backlight quirks
      drm: panel-backlight-quirks: Add Framework 13 matte panel
      drm/amd/display: Add support for minimum backlight quirk

 Documentation/gpu/drm-kms-helpers.rst             |  3 +
 drivers/gpu/drm/Kconfig                           |  4 ++
 drivers/gpu/drm/Makefile                          |  1 +
 drivers/gpu/drm/amd/amdgpu/Kconfig                |  1 +
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 10 +++
 drivers/gpu/drm/drm_panel_backlight_quirks.c      | 77 +++++++++++++++++++++++
 include/drm/drm_utils.h                           |  3 +
 7 files changed, 99 insertions(+)
---
base-commit: d74da846046aeec9333e802f5918bd3261fb5509
change-id: 20240610-amdgpu-min-backlight-quirk-8402fd8e736a

Best regards,
-- 
Thomas Weißschuh <linux at weissschuh.net>