[PATCH 08/25] drm/i915/pmu: Always sample an active ringbuffer

Chris Wilson
2019-02-19T12:22:45Z

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.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
---
drivers/gpu/drm/i915/i915_pmu.c | 60 ++++++++++---------------
drivers/gpu/drm/i915/intel_ringbuffer.h | 2 +-
2 files changed, 24 insertions(+), 38 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_pmu.c b/drivers/gpu/drm/i915/i915_pmu.c
index 13d70b90dd0f..21adad72bd86 100644
--- 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 +160,43 @@ 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;

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;

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);
+ /*
+ * MI_MODE reports IDLE if the ring is waiting, but we regard
+ * this as being busy instead, as the engine is busy with the
+ * user request.
+ */
+ 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);
+ }

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 710ffb221775..5d45ad4ecca9 100644
--- 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.
*