[Intel-gfx] [RFC 1/8] drm/i915: Introduce intel_runtime_pm_disable to pair intel_runtime_pm_enable

[Imre Deak]

On Fri, Aug 10, 2018 at 08:11:31AM +0100, Chris Wilson wrote:
> Currently, we cancel the extra wakeref we have for !runtime-pm devices
> inside power_wells_fini_hw. However, this is not strictly paired with
> the acquisition of that wakeref in runtime_pm_enable (as the fini_hw may
> be called on errors paths before we even call runtime_pm_enable). Make
> the symmetry more explicit and include a check that we do release all of
> our rpm wakerefs.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/i915_drv.c         |  8 ++++++--
>  drivers/gpu/drm/i915/intel_drv.h        |  1 +
>  drivers/gpu/drm/i915/intel_runtime_pm.c | 24 +++++++++++++++---------
>  3 files changed, 22 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index 9dce55182c3a..62ef105a241d 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -1281,6 +1281,8 @@ static void i915_driver_register(struct drm_i915_private *dev_priv)
>  	 */
>  	if (INTEL_INFO(dev_priv)->num_pipes)
>  		drm_kms_helper_poll_init(dev);
> +
> +	intel_runtime_pm_enable(dev_priv);
>  }
>  
>  /**
> @@ -1289,6 +1291,8 @@ static void i915_driver_register(struct drm_i915_private *dev_priv)
>   */
>  static void i915_driver_unregister(struct drm_i915_private *dev_priv)
>  {
> +	intel_runtime_pm_disable(dev_priv);
> +
>  	intel_fbdev_unregister(dev_priv);
>  	intel_audio_deinit(dev_priv);
>  
> @@ -1408,8 +1412,6 @@ int i915_driver_load(struct pci_dev *pdev, const struct pci_device_id *ent)
>  
>  	i915_driver_register(dev_priv);
>  
> -	intel_runtime_pm_enable(dev_priv);
> -
>  	intel_init_ipc(dev_priv);
>  
>  	intel_runtime_pm_put(dev_priv);
> @@ -1474,6 +1476,8 @@ void i915_driver_unload(struct drm_device *dev)
>  	i915_driver_cleanup_mmio(dev_priv);
>  
>  	intel_display_power_put(dev_priv, POWER_DOMAIN_INIT);
> +
> +	WARN_ON(atomic_read(&dev_priv->runtime_pm.wakeref_count));

This probably WARNs atm at least due to having a low-level
pm_runtime_put_autosuspend() in intel_runtime_pm_enable(); but a
corresponding intel_runtime_pm_get() in intel_power_domains_fini_hw() (via
intel_display_set_init_power) which is i915 specific. The following
would fix that:

diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
index e209edbc561d..1623c0d2cf57 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.c
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
@@ -3806,6 +3806,10 @@ void intel_power_domains_fini_hw(struct drm_i915_private *dev_priv)
 	 */
 	intel_display_set_init_power(dev_priv, true);
 
+	/* Hand over RPM reference to PM core */
+	pm_runtime_get_noresume(kdev);
+	intel_runtime_pm_put(dev_priv);
+
 	/* Remove the refcount we took to keep power well support disabled. */
 	if (!i915_modparams.disable_power_well)
 		intel_display_power_put(dev_priv, POWER_DOMAIN_INIT);

>  }
>  
>  static void i915_driver_release(struct drm_device *dev)
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 0601abb8c71f..dc6c0cec9b36 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -1956,6 +1956,7 @@ void intel_power_domains_verify_state(struct drm_i915_private *dev_priv);
>  void bxt_display_core_init(struct drm_i915_private *dev_priv, bool resume);
>  void bxt_display_core_uninit(struct drm_i915_private *dev_priv);
>  void intel_runtime_pm_enable(struct drm_i915_private *dev_priv);
> +void intel_runtime_pm_disable(struct drm_i915_private *dev_priv);
>  const char *
>  intel_display_power_domain_str(enum intel_display_power_domain domain);
>  
> diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
> index e209edbc561d..b78c3b48aa62 100644
> --- a/drivers/gpu/drm/i915/intel_runtime_pm.c
> +++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
> @@ -3793,8 +3793,6 @@ void intel_power_domains_init_hw(struct drm_i915_private *dev_priv, bool resume)
>   */
>  void intel_power_domains_fini_hw(struct drm_i915_private *dev_priv)
>  {
> -	struct device *kdev = &dev_priv->drm.pdev->dev;
> -
>  	/*
>  	 * The i915.ko module is still not prepared to be loaded when
>  	 * the power well is not enabled, so just enable it in case
> @@ -3809,13 +3807,6 @@ void intel_power_domains_fini_hw(struct drm_i915_private *dev_priv)
>  	/* Remove the refcount we took to keep power well support disabled. */
>  	if (!i915_modparams.disable_power_well)
>  		intel_display_power_put(dev_priv, POWER_DOMAIN_INIT);
> -
> -	/*
> -	 * Remove the refcount we took in intel_runtime_pm_enable() in case
> -	 * the platform doesn't support runtime PM.
> -	 */
> -	if (!HAS_RUNTIME_PM(dev_priv))
> -		pm_runtime_put(kdev);
>  }
>  
>  /**
> @@ -4074,3 +4065,18 @@ void intel_runtime_pm_enable(struct drm_i915_private *dev_priv)
>  	 */
>  	pm_runtime_put_autosuspend(kdev);
>  }
> +
> +void intel_runtime_pm_disable(struct drm_i915_private *dev_priv)
> +{
> +	struct pci_dev *pdev = dev_priv->drm.pdev;
> +	struct device *kdev = &pdev->dev;
> +
> +	pm_runtime_dont_use_autosuspend(kdev);
> +
> +	/*
> +	 * Remove the refcount we took in intel_runtime_pm_enable() in case
> +	 * the platform doesn't support runtime PM.
> +	 */
> +	if (!HAS_RUNTIME_PM(dev_priv))
> +		pm_runtime_put(kdev);
> +}
> -- 
> 2.18.0
>