[Intel-gfx] [PATCH 5/5] drm/i915/ilk: Move register read under spinlock

[Tvrtko Ursulin]

From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

Code does read-modify-write but the read was outside the lock.

It is fine since the caller holds struct mutex, but if we
correct this we open up the opportunity for decreasing the
mutex duration time since the call to ironlake_enable_drps
does not need it any longer since it is covered by the
mchdev_lock lock.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/intel_pm.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 8e869f183404..b63cdb23b222 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -4116,11 +4116,13 @@ bool ironlake_set_drps(struct drm_device *dev, u8 val)
 static void ironlake_enable_drps(struct drm_device *dev)
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
-	u32 rgvmodectl = I915_READ(MEMMODECTL);
+	u32 rgvmodectl;
 	u8 fmax, fmin, fstart, vstart;
 
 	spin_lock_irq(&mchdev_lock);
 
+	rgvmodectl = I915_READ(MEMMODECTL);
+
 	/* Enable temp reporting */
 	I915_WRITE16(PMMISC, I915_READ(PMMISC) | MCPPCE_EN);
 	I915_WRITE16(TSC1, I915_READ(TSC1) | TSE);
@@ -6240,8 +6242,8 @@ void intel_enable_gt_powersave(struct drm_device *dev)
 		return;
 
 	if (IS_IRONLAKE_M(dev)) {
-		mutex_lock(&dev->struct_mutex);
 		ironlake_enable_drps(dev);
+		mutex_lock(&dev->struct_mutex);
 		intel_init_emon(dev);
 		mutex_unlock(&dev->struct_mutex);
 	} else if (INTEL_INFO(dev)->gen >= 6) {
-- 
1.9.1