drm/amd/display: Initialise backlight level values from hw

commit 52d3d115e9cc975b90b1fc49abf6d36ad5e8847a upstream.

Internal backlight levels are initialised from ACPI but the values
are sometimes out of sync with the levels in effect until there has
been a read from hardware (eg triggered by reading from sysfs).

This means that the first drm_commit can cause the levels to be set
to a different value than the actual starting one, which results in
a sudden change in brightness.

This path shows the problem (when the values are out of sync):

   amdgpu_dm_atomic_commit_tail()
   -> amdgpu_dm_commit_streams()
   -> amdgpu_dm_backlight_set_level(..., dm->brightness[n])

This patch calls the backlight ops get_brightness explicitly
at the end of backlight registration to make sure dm->brightness[n]
is in sync with the actual hardware levels.

Fixes: 2fe87f54abdc ("drm/amd/display: Set default brightness according to ACPI")
Signed-off-by: Vivek Das Mohapatra <vivek@collabora.com>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 318b1c36d82a0cd2b06a4bb43272fa6f1bc8adc1)
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

0 files changed, 0 insertions, 0 deletions