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

[David Henningsson <david.henningsson@canonical.com>]

On 06/24/2013 04:18 PM, mengdong.lin@intel.com wrote:
> From: Mengdong Lin <mengdong.lin@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.

Thanks, but there seems to be no such checking of the ClkStopOK as you 
describe in the patch? Or am I missing something?

>
> 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.
>
> Signed-off-by: Mengdong Lin <mengdong.lin@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;
>   }
>



-- 
David Henningsson, Canonical Ltd.
https://launchpad.net/~diwic