Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
> This reverts commit 0b702dca26580e3bbfbbaf22dfc29280b6263414.
>
> CI reports that this is not as reliable as it first appears, with
> failures starting to sporadically occur in selftests.
>
> Fixes: 0b702dca2658 ("drm/i915: Avoid waking the engines just to check if they are idle")
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxx>
> Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
> Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
Reviewed-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/intel_engine_cs.c | 17 ++++++-----------
> 1 file changed, 6 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
> index 4f244019560d..b7b626195eda 100644
> --- a/drivers/gpu/drm/i915/intel_engine_cs.c
> +++ b/drivers/gpu/drm/i915/intel_engine_cs.c
> @@ -968,7 +968,6 @@ static bool ring_is_idle(struct intel_engine_cs *engine)
> {
> struct drm_i915_private *dev_priv = engine->i915;
> intel_wakeref_t wakeref;
> - unsigned long flags;
> bool idle = true;
>
> if (I915_SELFTEST_ONLY(!engine->mmio_base))
> @@ -979,19 +978,15 @@ static bool ring_is_idle(struct intel_engine_cs *engine)
> if (!wakeref)
> return true;
>
> - spin_lock_irqsave(&dev_priv->uncore.lock, flags);
> + /* First check that no commands are left in the ring */
> + if ((I915_READ_HEAD(engine) & HEAD_ADDR) !=
> + (I915_READ_TAIL(engine) & TAIL_ADDR))
> + idle = false;
>
> - /*
> - * Check that no commands are left in the ring.
> - *
> - * If the engine is not awake, both reads return 0 as we do so without
> - * forcewake.
> - */
> - if ((I915_READ_FW(RING_HEAD(engine->mmio_base)) & HEAD_ADDR) !=
> - (I915_READ_FW(RING_TAIL(engine->mmio_base)) & TAIL_ADDR))
> + /* No bit for gen2, so assume the CS parser is idle */
> + if (INTEL_GEN(dev_priv) > 2 && !(I915_READ_MODE(engine) & MODE_IDLE))
> idle = false;
>
> - spin_unlock_irqrestore(&dev_priv->uncore.lock, flags);
> intel_runtime_pm_put(dev_priv, wakeref);
>
> return idle;
> --
> 2.20.1
>
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