drm/radeon: disable native backlight control on pre-r6xx asics (v2)

commit b7bc596ebbe0cddc97d76ef9309f64471bbf13eb upstream.

Just use the acpi interface.  That's what windows uses on this
generation and it's the only thing that seems to work reliably
on these generation parts.

You can still force the native backlight interface by setting
radeon.backlight=1

Bug:
https://bugzilla.kernel.org/show_bug.cgi?id=88501

v2: merge into above if/else block

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/radeon/radeon_encoders.c b/drivers/gpu/drm/radeon/radeon_encoders.c
index 15edf23b465c2ba90cca2f2ffb7c242971bda2bf..1ca64b615fc05fa4d2e40ce172adba2f109dc788 100644 (file)
--- a/drivers/gpu/drm/radeon/radeon_encoders.c
+++ b/drivers/gpu/drm/radeon/radeon_encoders.c
@@ -179,6 +179,9 @@ static void radeon_encoder_add_backlight(struct radeon_encoder *radeon_encoder,
                    (rdev->pdev->subsystem_vendor == 0x1734) &&
                    (rdev->pdev->subsystem_device == 0x1107))
                        use_bl = false;
+               /* disable native backlight control on older asics */
+               else if (rdev->family < CHIP_R600)
+                       use_bl = false;
                else
                        use_bl = true;
        }