[alsa-devel] [PATCH v2] ASoC: codec: hdac_hdmi add device_link to card device

[Pierre-Louis Bossart]

On 4/13/19 8:18 AM, libin.yang at intel.com wrote:
> From: Libin Yang <libin.yang at intel.com>
> 
> In resume from S3, HDAC HDMI codec driver dapm event callback may be
> operated before HDMI codec driver turns on the display audio power
> domain because of the contest between display driver and hdmi codec driver.
> 
> This patch adds the device_link between soc card device (consumer) and
> hdmi codec device (supplier) to make sure the sequence is always correct.
> 
> Signed-off-by: Libin Yang <libin.yang at intel.com>

Acked-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>

Libin, please follow-up on the question from Takashi on CC:ing to 
stable. I would guess this probably would be needed for 4.14+, older 
stuff is unlikely to work anyways due to other issues.

> ---
>   sound/soc/codecs/hdac_hdmi.c | 11 +++++++++++
>   1 file changed, 11 insertions(+)
> 
> diff --git a/sound/soc/codecs/hdac_hdmi.c b/sound/soc/codecs/hdac_hdmi.c
> index 5eeb0fe..4de1fbf 100644
> --- a/sound/soc/codecs/hdac_hdmi.c
> +++ b/sound/soc/codecs/hdac_hdmi.c
> @@ -1855,6 +1855,17 @@ static int hdmi_codec_probe(struct snd_soc_component *component)
>   	hdmi->card = dapm->card->snd_card;
>   
>   	/*
> +	 * Setup a device_link between card device and HDMI codec device.
> +	 * The card device is the consumer and the HDMI codec device is
> +	 * the supplier. With this setting, we can make sure that the audio
> +	 * domain in display power will be always turned on before operating
> +	 * on the HDMI audio codec registers.
> +	 * Let's use the flag DL_FLAG_AUTOREMOVE_CONSUMER. This can make
> +	 * sure the device link is freed when the machine driver is removed.
> +	 */
> +	device_link_add(component->card->dev, &hdev->dev, DL_FLAG_RPM_ACTIVE |
> +			DL_FLAG_AUTOREMOVE_CONSUMER);
> +	/*
>   	 * hdac_device core already sets the state to active and calls
>   	 * get_noresume. So enable runtime and set the device to suspend.
>   	 */
>