[PATCH v23 24/32] ASoC: qcom: qdsp6: Add PCM ops to track current state

[Wesley Cheng <quic_wcheng@xxxxxxxxxxx>]

Register PCM callbacks so that the Q6USB DPCM backend dai link can track
and update the status of the PCM device.  Utilize the SOC USB state APIs to
ensure that the SND kcontrol for the offload status is updated properly.

Signed-off-by: Wesley Cheng <quic_wcheng@xxxxxxxxxxx>
---
 sound/soc/qcom/qdsp6/q6usb.c | 52 +++++++++++++++++++++++++++++++++---
 1 file changed, 49 insertions(+), 3 deletions(-)

diff --git a/sound/soc/qcom/qdsp6/q6usb.c b/sound/soc/qcom/qdsp6/q6usb.c
index 5877f132f5f5..2715ac920273 100644
--- a/sound/soc/qcom/qdsp6/q6usb.c
+++ b/sound/soc/qcom/qdsp6/q6usb.c
@@ -30,6 +30,9 @@
 struct q6usb_status {
 	struct snd_soc_usb_device *sdev;
 	unsigned int pcm_index;
+	bool prepared;
+	bool running;
+	int session_id;
 };
 
 struct q6usb_port_data {
@@ -81,14 +84,48 @@ static int q6usb_hw_params(struct snd_pcm_substream *substream,
 		goto out;
 
 	data->status[data->sel_card_idx].pcm_index = data->sel_pcm_idx;
+	data->status[data->sel_card_idx].prepared = true;
+	data->status[data->sel_card_idx].session_id =
+		snd_soc_usb_prepare_session(data->usb, data->sel_card_idx,
+						data->sel_pcm_idx);
 out:
 	mutex_unlock(&data->mutex);
 
 	return ret;
 }
 
+static int q6usb_prepare(struct snd_pcm_substream *substream,
+		struct snd_soc_dai *dai)
+{
+	struct q6usb_port_data *data = dev_get_drvdata(dai->dev);
+
+	mutex_lock(&data->mutex);
+	data->status[data->sel_card_idx].running = true;
+	snd_soc_usb_set_session_state(data->usb,
+			data->status[data->sel_card_idx].session_id,
+			SND_SOC_USB_RUNNING);
+	mutex_unlock(&data->mutex);
+
+	return 0;
+}
+
+static void q6usb_shutdown(struct snd_pcm_substream *substream,
+				struct snd_soc_dai *dai)
+{
+	struct q6usb_port_data *data = dev_get_drvdata(dai->dev);
+
+	mutex_lock(&data->mutex);
+	data->status[data->sel_card_idx].running = false;
+	data->status[data->sel_card_idx].prepared = false;
+	snd_soc_usb_shutdown_session(data->usb,
+			data->status[data->sel_card_idx].session_id);
+	mutex_unlock(&data->mutex);
+}
+
 static const struct snd_soc_dai_ops q6usb_ops = {
 	.hw_params = q6usb_hw_params,
+	.prepare = q6usb_prepare,
+	.shutdown = q6usb_shutdown,
 };
 
 static struct snd_soc_dai_driver q6usb_be_dais[] = {
@@ -149,9 +186,14 @@ static int q6usb_put_offload_dev(struct snd_kcontrol *kcontrol,
 	int changed = 0;
 	int idx;
 
+	mutex_lock(&data->mutex);
+
+	/* Don't allow changes to the offloading devices if session is busy */
+	if (data->sel_card_idx >= 0 && data->status[data->sel_card_idx].prepared)
+		goto out;
+
 	idx = ucontrol->value.integer.value[0];
 
-	mutex_lock(&data->mutex);
 	switch (type) {
 	case SND_SOC_USB_KCTL_CARD_ROUTE:
 		if (idx >= 0 && test_bit(idx, &data->available_card_slot)) {
@@ -210,8 +252,12 @@ static int q6usb_alsa_connection_cb(struct snd_soc_usb *usb,
 
 	mutex_lock(&data->mutex);
 	if (connected) {
-		/* Selects the latest USB headset plugged in for offloading */
-		if (!data->idx_valid) {
+		/*
+		 * Select the latest USB headset plugged in, if session is
+		 * idle, and if no index selected by the kcontrol.
+		 */
+		if (!data->idx_valid &&
+			!data->status[data->sel_card_idx].prepared) {
 			data->sel_card_idx = sdev->card_idx;
 			data->sel_pcm_idx = 0;
 		}