From: Nicholas Bishop <nicholasbishop@xxxxxxxxxx> commit 364438fd629f7611a84c8e6d7de91659300f1502 upstream. 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@xxxxxxxxxx> Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/gpu/drm/radeon/atombios_encoders.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/drivers/gpu/drm/radeon/atombios_encoders.c +++ b/drivers/gpu/drm/radeon/atombios_encoders.c @@ -193,7 +193,8 @@ void radeon_atom_backlight_init(struct r * 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)
