drm/radeon/kms/pm: bail early if nothing's changing

If we aren't changing the power state, no need to take
locks and schedule fences, etc.

There seem to be lock ordering issues in the CP and
fence code in some cases; see bug 29140 below.

Fixes:
https://bugs.freedesktop.org/show_bug.cgi?id=29140
Possibly also:
https://bugzilla.kernel.org/show_bug.cgi?id=16581Signed-off-by: NAlex Deucher <alexdeucher@gmail.com>
Cc: stable@kernel.org
Signed-off-by: NDave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/radeon_pm.c

@@ -226,6 +226,11 @@ static void radeon_pm_set_clocks(struct radeon_device *rdev)
 {
 	int i;
 
+	/* no need to take locks, etc. if nothing's going to change */
+	if ((rdev->pm.requested_clock_mode_index == rdev->pm.current_clock_mode_index) &&
+	    (rdev->pm.requested_power_state_index == rdev->pm.current_power_state_index))
+		return;
+
 	mutex_lock(&rdev->ddev->struct_mutex);
 	mutex_lock(&rdev->vram_mutex);
 	mutex_lock(&rdev->cp.mutex);