[alsa-devel] [PATCH v2 3/3] ALSA: hda - implement a refcount for i915 power well switch

[Takashi Iwai]

At Tue, 28 Apr 2015 20:43:19 +0800,
mengdong.lin at intel.com wrote:
> 
> From: Mengdong Lin <mengdong.lin at intel.com>
> 
> This is to check the refcount of audio driver and reduce calling to i915.

This has to be implemented before patch 1 & 2, I suppose.

But, you don't mention about the new mutex at all.  Why do you need
it?


Takashi

> 
> Signed-off-by: Mengdong Lin <mengdong.lin at intel.com>
> 
> diff --git a/sound/pci/hda/hda_i915.c b/sound/pci/hda/hda_i915.c
> index 52a85d8..e831691 100644
> --- a/sound/pci/hda/hda_i915.c
> +++ b/sound/pci/hda/hda_i915.c
> @@ -42,11 +42,16 @@ int hda_display_power(struct hda_intel *hda, bool enable)
>  
>  	dev_dbg(&hda->chip.pci->dev, "display power %s\n",
>  		enable ? "enable" : "disable");
> -	if (enable)
> -		acomp->ops->get_power(acomp->dev);
> -	else
> -		acomp->ops->put_power(acomp->dev);
> -
> +	mutex_lock(&hda->display_power.lock);
> +	if (enable) {
> +		if (!hda->display_power.use_count++)
> +			acomp->ops->get_power(acomp->dev);
> +	} else {
> +		WARN_ON(!hda->display_power.use_count);
> +		if (!--hda->display_power.use_count)
> +			acomp->ops->put_power(acomp->dev);
> +	}
> +	mutex_unlock(&hda->display_power.lock);
>  	return 0;
>  }
>  
> @@ -171,6 +176,8 @@ int hda_i915_init(struct hda_intel *hda)
>  
>  	dev_dbg(dev, "bound to i915 component master\n");
>  
> +	mutex_init(&hda->display_power.lock);
> +
>  	return 0;
>  out_master_del:
>  	component_master_del(dev, &hda_component_master_ops);
> diff --git a/sound/pci/hda/hda_intel.h b/sound/pci/hda/hda_intel.h
> index 2069898..3ca000a 100644
> --- a/sound/pci/hda/hda_intel.h
> +++ b/sound/pci/hda/hda_intel.h
> @@ -19,6 +19,11 @@
>  #include <drm/i915_component.h>
>  #include "hda_controller.h"
>  
> +struct i915_display_power {
> +	struct mutex lock;
> +	int use_count;
> +};
> +
>  struct hda_intel {
>  	struct azx chip;
>  
> @@ -46,6 +51,7 @@ struct hda_intel {
>  
>  	/* i915 component interface */
>  	struct i915_audio_component audio_component;
> +	struct i915_display_power display_power;
>  };
>  
>  #ifdef CONFIG_SND_HDA_I915
> -- 
> 1.9.1
>