Quoting Sagar Arun Kamble (2017-10-06 13:13:40)
> Defined new struct intel_rc6 to hold RC6 specific state and
> intel_ring_pstate to hold ring specific state.
>
> v2: s/intel_ring_pstate/intel_llc_pstate and rebase. (Chris)
>
> Signed-off-by: Sagar Arun Kamble <sagar.a.kamble@xxxxxxxxx>
> Cc: Imre Deak <imre.deak@xxxxxxxxx>
> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
> Cc: Radoslaw Szwichtenberg <radoslaw.szwichtenberg@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_drv.c | 2 +-
> drivers/gpu/drm/i915/i915_drv.h | 10 ++++++++
> drivers/gpu/drm/i915/intel_pm.c | 57 +++++++++++++++++++++++++++++++----------
> 3 files changed, 54 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index 470807c..154f231 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -2502,7 +2502,7 @@ static int intel_runtime_suspend(struct device *kdev)
> struct drm_i915_private *dev_priv = to_i915(dev);
> int ret;
>
> - if (WARN_ON_ONCE(!(dev_priv->pm.rps.enabled && intel_rc6_enabled())))
> + if (WARN_ON_ONCE(!(dev_priv->pm.rc6.enabled && intel_rc6_enabled())))
> return -ENODEV;
>
> if (WARN_ON_ONCE(!HAS_RUNTIME_PM(dev_priv)))
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 45944a8..a07aa71 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -1363,8 +1363,18 @@ struct intel_rps {
> struct intel_rps_ei ei;
> };
>
> +struct intel_rc6 {
> + bool enabled;
> +};
> +
> +struct intel_llc_pstate {
> + bool configured;
> +};
> +
> struct intel_gen6_power_mgmt {
> struct intel_rps rps;
> + struct intel_rc6 rc6;
> + struct intel_llc_pstate llc_pstate;
> struct delayed_work autoenable_work;
>
> /*
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index 03264fe..df36a6f 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -7873,7 +7873,12 @@ static void intel_init_emon(struct drm_i915_private *dev_priv)
>
> static inline void intel_update_ring_freq(struct drm_i915_private *i915)
> {
> + if (READ_ONCE(i915->pm.llc_pstate.configured))
> + return;
Tell me about how you expect the locking around this function to be.
The READ_ONCE() implies that we are doing a optimistic peek outside of a
lock, but then we set configured without acquiring a lock, so I assume
we are inside some lock.
That looks true for all, we don't need READ_ONCE() anymore as we only
inspect inside the mutex (and so READ_ONCE is giving the wrong
impression).
> +
> gen6_update_ring_freq(i915);
> +
> + i915->pm.llc_pstate.configured = true;
> }
>
> void intel_disable_gt_powersave(struct drm_i915_private *dev_priv)
> {
> - if (!READ_ONCE(dev_priv->pm.rps.enabled))
> - return;
> -
> mutex_lock(&dev_priv->pm.pcu_lock);
>
> intel_disable_rc6(dev_priv);
> intel_disable_rps(dev_priv);
> + if (HAS_LLC(dev_priv))
> + dev_priv->pm.llc_pstate.configured = false;
Always clear it? If no llc, it can never be configured.
Hmm, better if we just made it symmetrical with
s/intel_update_ring_freq/intel_enable_llc_pstate/ and
intel_disable_llc_pstate here.
>
> - dev_priv->pm.rps.enabled = false;
> mutex_unlock(&dev_priv->pm.pcu_lock);
> }
> @@ -8080,7 +8103,10 @@ static void __intel_autoenable_gt_powersave(struct work_struct *work)
> struct intel_engine_cs *rcs;
> struct drm_i915_gem_request *req;
>
> - if (READ_ONCE(dev_priv->pm.rps.enabled))
> + if (READ_ONCE(dev_priv->pm.rps.enabled) &&
> + READ_ONCE(dev_priv->pm.rc6.enabled) &&
> + !(HAS_LLC(dev_priv) ^
> + READ_ONCE(dev_priv->pm.llc_pstate.configured)))
> goto out;
This optimisation has lost its appeal :)
Kill it, if we need something like it we can try again later.
-Chris
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