drm/amd/display: Get backlight from PWM if DMCU is not initialized

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On Carrizo/Stoney systems we set backlight through panel_cntl, i.e.
directly via the PWM registers, if DMCU is not initialized. We
always read it back through ABM registers which leads to a
mismatch and forces atomic_commit to program the backlight
each time.

Instead make sure we use the same logic for backlight readback,
i.e. read it from panel_cntl if DMCU is not initialized.

We also need to remove some extraneous and incorrect calculations
at the end of dce_get_16_bit_backlight_from_pwm.

Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1666
Cc: stable@vger.kernel.org

Reviewed-by: Josip Pavic <josip.pavic@amd.com>
Acked-by: Mikita Lipski <mikita.lipski@amd.com>
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

...

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Harry Wentland 2021-08-16 15:57:12 -04:00 • committed by Alex Deucher

parent 7b89bf8318

commit 9e0d55ae54

2 changed files with 12 additions and 14 deletions

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16

drivers/gpu/drm/amd/display/dc/core/dc_link.c

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10

drivers/gpu/drm/amd/display/dc/dce/dce_panel_cntl.c

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