drm/radeon: Fix backlight control on iMac 12,1

The iMac 12,1 does not use the gmux driver for backlight, so the radeon
backlight device is needed to set the brightness.

Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1838
Signed-off-by: Nicholas Bishop <nicholasbishop@google.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

diff --git a/drivers/gpu/drm/radeon/atombios_encoders.c b/drivers/gpu/drm/radeon/atombios_encoders.c
index 0fce73b9a64691ae0dbfd8b2f597d633a31d1df0..70bd84b7ef2b0a2bcf27a051d1c85c2e5cee09ed 100644 (file)
--- a/drivers/gpu/drm/radeon/atombios_encoders.c
+++ b/drivers/gpu/drm/radeon/atombios_encoders.c
@@ -198,7 +198,8 @@ void radeon_atom_backlight_init(struct radeon_encoder *radeon_encoder,
         * so don't register a backlight device
         */
        if ((rdev->pdev->subsystem_vendor == PCI_VENDOR_ID_APPLE) &&
-           (rdev->pdev->device == 0x6741))
+           (rdev->pdev->device == 0x6741) &&
+           !dmi_match(DMI_PRODUCT_NAME, "iMac12,1"))
                return;
 
        if (!radeon_encoder->enc_priv)