drm/radeon/evergreen+: wait for the MC to settle after MC blackout

commit ed39fadd upstream.

Some chips seem to need a little delay after blacking out
the MC before the requests actually stop.

May fix:
https://bugs.freedesktop.org/show_bug.cgi?id=56139
https://bugs.freedesktop.org/show_bug.cgi?id=57567Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/gpu/drm/radeon/evergreen.c

@@ -1065,6 +1065,8 @@ void evergreen_mc_stop(struct radeon_device *rdev, struct evergreen_mc_save *sav
 		WREG32(EVERGREEN_D5VGA_CONTROL, 0);
 		WREG32(EVERGREEN_D6VGA_CONTROL, 0);
 	}
+	/* wait for the MC to settle */
+	udelay(100);
 }
 
 void evergreen_mc_resume(struct radeon_device *rdev, struct evergreen_mc_save *save)