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drm/i915/pmu: Only use exclusive mmio access for gen7 

On gen7, we have to avoid concurrent access to the same mmio cacheline,
and so coordinate all mmio access with the uncore->lock. However, for
pmu, we want to avoid perturbing the system and disabling interrupts
unnecessarily, so restrict the w/a to gen7 where it is requied to
prevent machine hangs.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191108103511.20951-2-chris@chris-wilson.co.uk
This commit is contained in:
Chris Wilson 2019-11-08 10:35:11 +00:00
parent c1c82d267a
commit d79e1bd676
1 changed files with 19 additions and 2 deletions
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21
drivers/gpu/drm/i915/i915_pmu.c
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@ -292,6 +292,16 @@ add_sample(struct i915_pmu_sample *sample, u32 val)
sample->cur += val;
}
static bool exclusive_mmio_access(const struct drm_i915_private *i915)
{
/*
* We have to avoid concurrent mmio cache line access on gen7 or
* risk a machine hang. For a fun history lesson dig out the old
* userspace intel_gpu_top and run it on Ivybridge or Haswell!
*/
return IS_GEN(i915, 7);
}
static void
engines_sample(struct intel_gt *gt, unsigned int period_ns)
{
@ -304,6 +314,7 @@ engines_sample(struct intel_gt *gt, unsigned int period_ns)
for_each_engine(engine, gt, id) {
struct intel_engine_pmu *pmu = &engine->pmu;
spinlock_t *mmio_lock;
unsigned long flags;
bool busy;
u32 val;
@ -311,7 +322,12 @@ engines_sample(struct intel_gt *gt, unsigned int period_ns)
if (!intel_engine_pm_get_if_awake(engine))
continue;
spin_lock_irqsave(&engine->uncore->lock, flags);
mmio_lock = NULL;
if (exclusive_mmio_access(i915))
mmio_lock = &engine->uncore->lock;
if (unlikely(mmio_lock))
spin_lock_irqsave(mmio_lock, flags);
val = ENGINE_READ_FW(engine, RING_CTL);
if (val == 0) /* powerwell off => engine idle */
@ -342,7 +358,8 @@ engines_sample(struct intel_gt *gt, unsigned int period_ns)
add_sample(&pmu->sample[I915_SAMPLE_BUSY], period_ns);
skip:
spin_unlock_irqrestore(&engine->uncore->lock, flags);
if (unlikely(mmio_lock))
spin_unlock_irqrestore(mmio_lock, flags);
intel_engine_pm_put(engine);
}
}