drm/i915: Only grab timestamps when needed

No need to call ktime_get_raw_ns twice per unlimited wait and can
also elimate a local variable.

v2: Added comment about silencing the compiler warning. (Daniel Vetter)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Dave Gordon <david.s.gordon@intel.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1452870672-13901-1-git-send-email-tvrtko.ursulin@linux.intel.com

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index ddc21d4b388d2419a63fbd4f4a5745deea80957b..6b0102da859c8fae0bc8ca6e67fef4b266c51c06 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1251,7 +1251,7 @@ int __i915_wait_request(struct drm_i915_gem_request *req,
        int state = interruptible ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE;
        DEFINE_WAIT(wait);
        unsigned long timeout_expire;
-       s64 before, now;
+       s64 before = 0; /* Only to silence a compiler warning. */
        int ret;
 
        WARN(!intel_irqs_enabled(dev_priv), "IRQs disabled");
@@ -1271,14 +1271,17 @@ int __i915_wait_request(struct drm_i915_gem_request *req,
                        return -ETIME;
 
                timeout_expire = jiffies + nsecs_to_jiffies_timeout(*timeout);
+
+               /*
+                * Record current time in case interrupted by signal, or wedged.
+                */
+               before = ktime_get_raw_ns();
        }
 
        if (INTEL_INFO(dev_priv)->gen >= 6)
                gen6_rps_boost(dev_priv, rps, req->emitted_jiffies);
 
-       /* Record current time in case interrupted by signal, or wedged */
        trace_i915_gem_request_wait_begin(req);
-       before = ktime_get_raw_ns();
 
        /* Optimistic spin for the next jiffie before touching IRQs */
        ret = __i915_spin_request(req, state);
@@ -1343,11 +1346,10 @@ int __i915_wait_request(struct drm_i915_gem_request *req,
        finish_wait(&ring->irq_queue, &wait);
 
 out:
-       now = ktime_get_raw_ns();
        trace_i915_gem_request_wait_end(req);
 
        if (timeout) {
-               s64 tres = *timeout - (now - before);
+               s64 tres = *timeout - (ktime_get_raw_ns() - before);
 
                *timeout = tres < 0 ? 0 : tres;