[alsa-devel] [RFC PATCH] ALSA: hda - reset hda link during system/runtime suspend

[Takashi Iwai]

At Mon, 24 Jun 2013 10:18:54 -0400,
mengdong.lin at intel.com wrote:
> 
> From: Mengdong Lin <mengdong.lin at intel.com>
> 
> If all the codecs report ClkStopOK (OK to stop bus clock) after being put to
> D3, this patch will reset the HDA link before the controller is put to D3.
> 
> So the link will be in reset during system or runtime suspend, the bus clock
> stops and the codecs are in D3(ClkStop) state.
> 
> This may help to reduce power consumption by dozens of mW on some peripheral
> hda codecs.

Do you have the actually measured result, or is it just a hypothesis?

The patch looks safe, so I'm going to apply it, but would like to know
the influence.


thanks,

Takashi

> 
> Signed-off-by: Mengdong Lin <mengdong.lin at intel.com>
> 
> diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
> index f089fa0..9f110c7 100644
> --- a/sound/pci/hda/hda_intel.c
> +++ b/sound/pci/hda/hda_intel.c
> @@ -1120,6 +1120,20 @@ static void azx_load_dsp_cleanup(struct hda_bus *bus,
>  				 struct snd_dma_buffer *dmab);
>  #endif
>  
> +/* enter link reset */
> +static void azx_reset_link(struct azx *chip)
> +{
> +	unsigned long timeout;
> +
> +	/* reset controller */
> +	azx_writel(chip, GCTL, azx_readl(chip, GCTL) & ~ICH6_GCTL_RESET);
> +
> +	timeout = jiffies + msecs_to_jiffies(100);
> +	while ((azx_readb(chip, GCTL) & ICH6_GCTL_RESET) &&
> +			time_before(jiffies, timeout))
> +		usleep_range(500, 1000);
> +}
> +
>  /* reset codec link */
>  static int azx_reset(struct azx *chip, int full_reset)
>  {
> @@ -2894,6 +2908,7 @@ static int azx_suspend(struct device *dev)
>  	if (chip->initialized)
>  		snd_hda_suspend(chip->bus);
>  	azx_stop_chip(chip);
> +	azx_reset_link(chip);
>  	if (chip->irq >= 0) {
>  		free_irq(chip->irq, chip);
>  		chip->irq = -1;
> @@ -2946,6 +2961,7 @@ static int azx_runtime_suspend(struct device *dev)
>  	struct azx *chip = card->private_data;
>  
>  	azx_stop_chip(chip);
> +	azx_reset_link(chip);
>  	azx_clear_irq_pending(chip);
>  	return 0;
>  }
> -- 
> 1.7.10.4
>