drm/radeon/DCE4+: clear bios scratch dpms bit (v2)

commit 6802d4ba upstream.

The BlankCrtc table in some DCE8 boards has some
logic shortcuts for the vbios when this bit is set.
Clear it for driver use.

v2: fix typo

Bug:
https://bugs.freedesktop.org/show_bug.cgi?id=73420Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/gpu/drm/radeon/radeon_atombios.c

@@ -2735,6 +2735,10 @@ void radeon_atom_initialize_bios_scratch_regs(struct drm_device *dev)
 	/* tell the bios not to handle mode switching */
 	bios_6_scratch |= ATOM_S6_ACC_BLOCK_DISPLAY_SWITCH;
 
+	/* clear the vbios dpms state */
+	if (ASIC_IS_DCE4(rdev))
+		bios_2_scratch &= ~ATOM_S2_DEVICE_DPMS_STATE;
+
 	if (rdev->family >= CHIP_R600) {
 		WREG32(R600_BIOS_2_SCRATCH, bios_2_scratch);
 		WREG32(R600_BIOS_6_SCRATCH, bios_6_scratch);