Re: [PATCH] drm/i915: Restore user forcewake domains across suspend

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On Wed, Aug 08, 2018 at 10:08:42PM +0100, Chris Wilson wrote:
> On suspend, we cancel the automatic forcewake and clear all other sources
> of forcewake so the machine can sleep before we do suspend. However, we
> expose the forcewake to userspace (only via debugfs, but nevertheless we
> do) and want to restore that upon resume or else our accounting will be
> off and we may not acquire the forcewake before we use it. So record
> which domains we cleared on suspend and reacquire them early on resume.
> 
> v2: Hold the spinlock to appease our sanitychecks
> 
> Reported-by: Imre Deak <imre.deak@xxxxxxxxxxxxxxx>
> Fixes: b8473050805f ("drm/i915: Fix forcewake active domain tracking")
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxx>
> Cc: Imre Deak <imre.deak@xxxxxxxxxxxxxxx>

The issue happens to fix itself by the first reg access needing an auto
FW during resume, but such an access isn't guaranteed:

Reviewed-by: Imre Deak <imre.deak@xxxxxxxxx>

> ---
>  drivers/gpu/drm/i915/intel_uncore.c           | 44 ++++++++++---------
>  drivers/gpu/drm/i915/intel_uncore.h           |  1 +
>  drivers/gpu/drm/i915/selftests/intel_uncore.c |  2 +-
>  3 files changed, 26 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
> index 284be151f645..cf40361fe181 100644
> --- a/drivers/gpu/drm/i915/intel_uncore.c
> +++ b/drivers/gpu/drm/i915/intel_uncore.c
> @@ -369,8 +369,8 @@ intel_uncore_fw_release_timer(struct hrtimer *timer)
>  }
>  
>  /* Note callers must have acquired the PUNIT->PMIC bus, before calling this. */
> -static void intel_uncore_forcewake_reset(struct drm_i915_private *dev_priv,
> -					 bool restore)
> +static unsigned int
> +intel_uncore_forcewake_reset(struct drm_i915_private *dev_priv)
>  {
>  	unsigned long irqflags;
>  	struct intel_uncore_forcewake_domain *domain;
> @@ -422,20 +422,11 @@ static void intel_uncore_forcewake_reset(struct drm_i915_private *dev_priv,
>  		dev_priv->uncore.funcs.force_wake_put(dev_priv, fw);
>  
>  	fw_domains_reset(dev_priv, dev_priv->uncore.fw_domains);
> -
> -	if (restore) { /* If reset with a user forcewake, try to restore */
> -		if (fw)
> -			dev_priv->uncore.funcs.force_wake_get(dev_priv, fw);
> -
> -		if (IS_GEN6(dev_priv) || IS_GEN7(dev_priv))
> -			dev_priv->uncore.fifo_count =
> -				fifo_free_entries(dev_priv);
> -	}
> -
> -	if (!restore)
> -		assert_forcewakes_inactive(dev_priv);
> +	assert_forcewakes_inactive(dev_priv);
>  
>  	spin_unlock_irqrestore(&dev_priv->uncore.lock, irqflags);
> +
> +	return fw; /* track the lost user forcewake domains */
>  }
>  
>  static u64 gen9_edram_size(struct drm_i915_private *dev_priv)
> @@ -544,7 +535,7 @@ check_for_unclaimed_mmio(struct drm_i915_private *dev_priv)
>  }
>  
>  static void __intel_uncore_early_sanitize(struct drm_i915_private *dev_priv,
> -					  bool restore_forcewake)
> +					  unsigned int restore_forcewake)
>  {
>  	/* clear out unclaimed reg detection bit */
>  	if (check_for_unclaimed_mmio(dev_priv))
> @@ -559,7 +550,17 @@ static void __intel_uncore_early_sanitize(struct drm_i915_private *dev_priv,
>  	}
>  
>  	iosf_mbi_punit_acquire();
> -	intel_uncore_forcewake_reset(dev_priv, restore_forcewake);
> +	intel_uncore_forcewake_reset(dev_priv);
> +	if (restore_forcewake) {
> +		spin_lock_irq(&dev_priv->uncore.lock);
> +		dev_priv->uncore.funcs.force_wake_get(dev_priv,
> +						      restore_forcewake);
> +
> +		if (IS_GEN6(dev_priv) || IS_GEN7(dev_priv))
> +			dev_priv->uncore.fifo_count =
> +				fifo_free_entries(dev_priv);
> +		spin_unlock_irq(&dev_priv->uncore.lock);
> +	}
>  	iosf_mbi_punit_release();
>  }
>  
> @@ -568,13 +569,16 @@ void intel_uncore_suspend(struct drm_i915_private *dev_priv)
>  	iosf_mbi_punit_acquire();
>  	iosf_mbi_unregister_pmic_bus_access_notifier_unlocked(
>  		&dev_priv->uncore.pmic_bus_access_nb);
> -	intel_uncore_forcewake_reset(dev_priv, false);
> +	dev_priv->uncore.fw_domains_user =
> +		intel_uncore_forcewake_reset(dev_priv);
>  	iosf_mbi_punit_release();
>  }
>  
>  void intel_uncore_resume_early(struct drm_i915_private *dev_priv)
>  {
> -	__intel_uncore_early_sanitize(dev_priv, true);
> +	__intel_uncore_early_sanitize(dev_priv,
> +				      dev_priv->uncore.fw_domains_user);
> +
>  	iosf_mbi_register_pmic_bus_access_notifier(
>  		&dev_priv->uncore.pmic_bus_access_nb);
>  	i915_check_and_clear_faults(dev_priv);
> @@ -1555,7 +1559,7 @@ void intel_uncore_init(struct drm_i915_private *dev_priv)
>  
>  	intel_uncore_edram_detect(dev_priv);
>  	intel_uncore_fw_domains_init(dev_priv);
> -	__intel_uncore_early_sanitize(dev_priv, false);
> +	__intel_uncore_early_sanitize(dev_priv, 0);
>  
>  	dev_priv->uncore.unclaimed_mmio_check = 1;
>  	dev_priv->uncore.pmic_bus_access_nb.notifier_call =
> @@ -1642,7 +1646,7 @@ void intel_uncore_fini(struct drm_i915_private *dev_priv)
>  	iosf_mbi_punit_acquire();
>  	iosf_mbi_unregister_pmic_bus_access_notifier_unlocked(
>  		&dev_priv->uncore.pmic_bus_access_nb);
> -	intel_uncore_forcewake_reset(dev_priv, false);
> +	intel_uncore_forcewake_reset(dev_priv);
>  	iosf_mbi_punit_release();
>  }
>  
> diff --git a/drivers/gpu/drm/i915/intel_uncore.h b/drivers/gpu/drm/i915/intel_uncore.h
> index 2fbe93178fb2..137d8ac856fe 100644
> --- a/drivers/gpu/drm/i915/intel_uncore.h
> +++ b/drivers/gpu/drm/i915/intel_uncore.h
> @@ -104,6 +104,7 @@ struct intel_uncore {
>  
>  	enum forcewake_domains fw_domains;
>  	enum forcewake_domains fw_domains_active;
> +	enum forcewake_domains fw_domains_user;
>  
>  	u32 fw_set;
>  	u32 fw_clear;
> diff --git a/drivers/gpu/drm/i915/selftests/intel_uncore.c b/drivers/gpu/drm/i915/selftests/intel_uncore.c
> index 47bc5b2ddb56..81d9d31042a9 100644
> --- a/drivers/gpu/drm/i915/selftests/intel_uncore.c
> +++ b/drivers/gpu/drm/i915/selftests/intel_uncore.c
> @@ -160,7 +160,7 @@ static int intel_uncore_check_forcewake_domains(struct drm_i915_private *dev_pri
>  		i915_reg_t reg = { offset };
>  
>  		iosf_mbi_punit_acquire();
> -		intel_uncore_forcewake_reset(dev_priv, false);
> +		intel_uncore_forcewake_reset(dev_priv);
>  		iosf_mbi_punit_release();
>  
>  		check_for_unclaimed_mmio(dev_priv);
> -- 
> 2.18.0
> 
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