drm/i915/pmu: Always sample an active ringbuffer

As we no longer have a precise indication of requests queued to an
engine, make no presumptions and just sample the ring registers to see
if the engine is busy.

v2: Report busy while the ring is idling on a semaphore/event.
v3: Give the struct a name!
v4: Always 0 outside the powerwell; trusting the powerwell is
accurate enough for our sampling pmu.
v5: Protect against gen7 mmio madness and try to improve grammar

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190223000102.14290-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/i915_pmu.c b/drivers/gpu/drm/i915/i915_pmu.c
index 13d70b9..6560c35 100644 (file)
--- a/drivers/gpu/drm/i915/i915_pmu.c
+++ b/drivers/gpu/drm/i915/i915_pmu.c
@@ -148,14 +148,6 @@ void i915_pmu_gt_unparked(struct drm_i915_private *i915)
        spin_unlock_irq(&i915->pmu.lock);
 }
 
-static bool grab_forcewake(struct drm_i915_private *i915, bool fw)
-{
-       if (!fw)
-               intel_uncore_forcewake_get(i915, FORCEWAKE_ALL);
-
-       return true;
-}
-
 static void
 add_sample(struct i915_pmu_sample *sample, u32 val)
 {
@@ -168,49 +160,48 @@ engines_sample(struct drm_i915_private *dev_priv, unsigned int period_ns)
        struct intel_engine_cs *engine;
        enum intel_engine_id id;
        intel_wakeref_t wakeref;
-       bool fw = false;
+       unsigned long flags;
 
        if ((dev_priv->pmu.enable & ENGINE_SAMPLE_MASK) == 0)
                return;
 
-       if (!dev_priv->gt.awake)
-               return;
-
-       wakeref = intel_runtime_pm_get_if_in_use(dev_priv);
+       wakeref = 0;
+       if (READ_ONCE(dev_priv->gt.awake))
+               wakeref = intel_runtime_pm_get_if_in_use(dev_priv);
        if (!wakeref)
                return;
 
+       spin_lock_irqsave(&dev_priv->uncore.lock, flags);
        for_each_engine(engine, dev_priv, id) {
-               u32 current_seqno = intel_engine_get_seqno(engine);
-               u32 last_seqno = intel_engine_last_submit(engine);
+               struct intel_engine_pmu *pmu = &engine->pmu;
+               bool busy;
                u32 val;
 
-               val = !i915_seqno_passed(current_seqno, last_seqno);
-
-               if (val)
-                       add_sample(&engine->pmu.sample[I915_SAMPLE_BUSY],
-                                  period_ns);
-
-               if (val && (engine->pmu.enable &
-                   (BIT(I915_SAMPLE_WAIT) | BIT(I915_SAMPLE_SEMA)))) {
-                       fw = grab_forcewake(dev_priv, fw);
-
-                       val = I915_READ_FW(RING_CTL(engine->mmio_base));
-               } else {
-                       val = 0;
-               }
+               val = I915_READ_FW(RING_CTL(engine->mmio_base));
+               if (val == 0) /* powerwell off => engine idle */
+                       continue;
 
                if (val & RING_WAIT)
-                       add_sample(&engine->pmu.sample[I915_SAMPLE_WAIT],
-                                  period_ns);
-
+                       add_sample(&pmu->sample[I915_SAMPLE_WAIT], period_ns);
                if (val & RING_WAIT_SEMAPHORE)
-                       add_sample(&engine->pmu.sample[I915_SAMPLE_SEMA],
-                                  period_ns);
-       }
+                       add_sample(&pmu->sample[I915_SAMPLE_SEMA], period_ns);
 
-       if (fw)
-               intel_uncore_forcewake_put(dev_priv, FORCEWAKE_ALL);
+               /*
+                * While waiting on a semaphore or event, MI_MODE reports the
+                * ring as idle. However, previously using the seqno, and with
+                * execlists sampling, we account for the ring waiting as the
+                * engine being busy. Therefore, we record the sample as being
+                * busy if either waiting or !idle.
+                */
+               busy = val & (RING_WAIT_SEMAPHORE | RING_WAIT);
+               if (!busy) {
+                       val = I915_READ_FW(RING_MI_MODE(engine->mmio_base));
+                       busy = !(val & MODE_IDLE);
+               }
+               if (busy)
+                       add_sample(&pmu->sample[I915_SAMPLE_BUSY], period_ns);
+       }
+       spin_unlock_irqrestore(&dev_priv->uncore.lock, flags);
 
        intel_runtime_pm_put(dev_priv, wakeref);
 }

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 710ffb2..5d45ad4 100644 (file)
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -392,7 +392,7 @@ struct intel_engine_cs {
                bool irq_armed;
        } breadcrumbs;
 
-       struct {
+       struct intel_engine_pmu {
                /**
                 * @enable: Bitmask of enable sample events on this engine.
                 *