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=16581

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Cc: stable@kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>

diff --git a/drivers/gpu/drm/radeon/radeon_pm.c b/drivers/gpu/drm/radeon/radeon_pm.c
index 58038f5cab38d4b0c31ac7c2abfbad9a18c533b2..477ba673e1b45530894b2b9bb6f087ff51f23c0a 100644 (file)
--- a/drivers/gpu/drm/radeon/radeon_pm.c
+++ b/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);