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

[libin.yang at intel.com]

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>
---
 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.
 	 */
-- 
2.7.4