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

[Alex Deucher]

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 at gmail.com>
Cc: stable at kernel.org
---
 drivers/gpu/drm/radeon/radeon_pm.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/radeon/radeon_pm.c b/drivers/gpu/drm/radeon/radeon_pm.c
index a3d25f4..9a8031b 100644
--- 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);
-- 
1.7.1.1