[PATCH v2 2/2] ALSA: usb: qcom: manage offload device usage

[Guan-Yu Lin <guanyulin@google.com>]

The Qualcomm USB audio offload driver currently does not report its offload
activity to the USB core. This prevents the USB core from properly tracking
active offload sessions, which could allow the device to auto-suspend while
audio offloading is in progress.

Integrate usb_offload_get() and usb_offload_put() calls into the offload
stream setup and teardown paths. Specifically, call usb_offload_get() when
initializing the event ring and usb_offload_put() when freeing it.

Since the updated usb_offload_get() and usb_offload_put() APIs require the
caller to hold the USB device lock, add the necessary device locking in
handle_uaudio_stream_req() and qmi_stop_session() to satisfy this
requirement.

Cc: stable@vger.kernel.org
Fixes: ef82a4803aab ("xhci: sideband: add api to trace sideband usage")
Signed-off-by: Guan-Yu Lin <guanyulin@google.com>
---
 sound/usb/qcom/qc_audio_offload.c | 102 ++++++++++++++++++------------
 1 file changed, 60 insertions(+), 42 deletions(-)

diff --git a/sound/usb/qcom/qc_audio_offload.c b/sound/usb/qcom/qc_audio_offload.c
index cfb30a195364..1da243662327 100644
--- a/sound/usb/qcom/qc_audio_offload.c
+++ b/sound/usb/qcom/qc_audio_offload.c
@@ -699,6 +699,7 @@ static void uaudio_event_ring_cleanup_free(struct uaudio_dev *dev)
 		uaudio_iommu_unmap(MEM_EVENT_RING, IOVA_BASE, PAGE_SIZE,
 				   PAGE_SIZE);
 		xhci_sideband_remove_interrupter(uadev[dev->chip->card->number].sb);
+		usb_offload_put(dev->udev);
 	}
 }
 
@@ -750,6 +751,7 @@ static void qmi_stop_session(void)
 	struct snd_usb_substream *subs;
 	struct usb_host_endpoint *ep;
 	struct snd_usb_audio *chip;
+	struct usb_device *udev;
 	struct intf_info *info;
 	int pcm_card_num;
 	int if_idx;
@@ -791,8 +793,13 @@ static void qmi_stop_session(void)
 			disable_audio_stream(subs);
 		}
 		atomic_set(&uadev[idx].in_use, 0);
-		guard(mutex)(&chip->mutex);
-		uaudio_dev_cleanup(&uadev[idx]);
+
+		udev = uadev[idx].udev;
+		if (udev) {
+			guard(device)(&udev->dev);
+			guard(mutex)(&chip->mutex);
+			uaudio_dev_cleanup(&uadev[idx]);
+		}
 	}
 }
 
@@ -1183,11 +1190,15 @@ static int uaudio_event_ring_setup(struct snd_usb_substream *subs,
 	er_pa = 0;
 
 	/* event ring */
+	ret = usb_offload_get(subs->dev);
+	if (ret < 0)
+		goto exit;
+
 	ret = xhci_sideband_create_interrupter(uadev[card_num].sb, 1, false,
 					       0, uaudio_qdev->data->intr_num);
 	if (ret < 0) {
 		dev_err(&subs->dev->dev, "failed to fetch interrupter\n");
-		goto exit;
+		goto put_offload;
 	}
 
 	sgt = xhci_sideband_get_event_buffer(uadev[card_num].sb);
@@ -1219,6 +1230,8 @@ static int uaudio_event_ring_setup(struct snd_usb_substream *subs,
 	mem_info->dma = 0;
 remove_interrupter:
 	xhci_sideband_remove_interrupter(uadev[card_num].sb);
+put_offload:
+	usb_offload_put(subs->dev);
 exit:
 	return ret;
 }
@@ -1483,6 +1496,7 @@ static int prepare_qmi_response(struct snd_usb_substream *subs,
 	uaudio_iommu_unmap(MEM_EVENT_RING, IOVA_BASE, PAGE_SIZE, PAGE_SIZE);
 free_sec_ring:
 	xhci_sideband_remove_interrupter(uadev[card_num].sb);
+	usb_offload_put(subs->dev);
 drop_sync_ep:
 	if (subs->sync_endpoint) {
 		uaudio_iommu_unmap(MEM_XFER_RING,
@@ -1528,6 +1542,7 @@ static void handle_uaudio_stream_req(struct qmi_handle *handle,
 	u8 pcm_card_num;
 	u8 pcm_dev_num;
 	u8 direction;
+	struct usb_device *udev = NULL;
 	int ret = 0;
 
 	if (!svc->client_connected) {
@@ -1597,50 +1612,53 @@ static void handle_uaudio_stream_req(struct qmi_handle *handle,
 
 	uadev[pcm_card_num].ctrl_intf = chip->ctrl_intf;
 
-	if (req_msg->enable) {
-		ret = enable_audio_stream(subs,
-					  map_pcm_format(req_msg->audio_format),
-					  req_msg->number_of_ch, req_msg->bit_rate,
-					  datainterval);
-
-		if (!ret)
-			ret = prepare_qmi_response(subs, req_msg, &resp,
-						   info_idx);
-		if (ret < 0) {
-			guard(mutex)(&chip->mutex);
-			subs->opened = 0;
-		}
-	} else {
-		info = &uadev[pcm_card_num].info[info_idx];
-		if (info->data_ep_pipe) {
-			ep = usb_pipe_endpoint(uadev[pcm_card_num].udev,
-					       info->data_ep_pipe);
-			if (ep) {
-				xhci_sideband_stop_endpoint(uadev[pcm_card_num].sb,
-							    ep);
-				xhci_sideband_remove_endpoint(uadev[pcm_card_num].sb,
-							      ep);
+	udev = subs->dev;
+	scoped_guard(device, &udev->dev) {
+		if (req_msg->enable) {
+			ret = enable_audio_stream(subs,
+						map_pcm_format(req_msg->audio_format),
+						req_msg->number_of_ch, req_msg->bit_rate,
+						datainterval);
+
+			if (!ret)
+				ret = prepare_qmi_response(subs, req_msg, &resp,
+							info_idx);
+			if (ret < 0) {
+				guard(mutex)(&chip->mutex);
+				subs->opened = 0;
+			}
+		} else {
+			info = &uadev[pcm_card_num].info[info_idx];
+			if (info->data_ep_pipe) {
+				ep = usb_pipe_endpoint(uadev[pcm_card_num].udev,
+							info->data_ep_pipe);
+				if (ep) {
+					xhci_sideband_stop_endpoint(uadev[pcm_card_num].sb,
+									ep);
+					xhci_sideband_remove_endpoint(uadev[pcm_card_num].sb,
+									ep);
+				}
+
+				info->data_ep_pipe = 0;
 			}
 
-			info->data_ep_pipe = 0;
-		}
-
-		if (info->sync_ep_pipe) {
-			ep = usb_pipe_endpoint(uadev[pcm_card_num].udev,
-					       info->sync_ep_pipe);
-			if (ep) {
-				xhci_sideband_stop_endpoint(uadev[pcm_card_num].sb,
-							    ep);
-				xhci_sideband_remove_endpoint(uadev[pcm_card_num].sb,
-							      ep);
+			if (info->sync_ep_pipe) {
+				ep = usb_pipe_endpoint(uadev[pcm_card_num].udev,
+							info->sync_ep_pipe);
+				if (ep) {
+					xhci_sideband_stop_endpoint(uadev[pcm_card_num].sb,
+									ep);
+					xhci_sideband_remove_endpoint(uadev[pcm_card_num].sb,
+									ep);
+				}
+
+				info->sync_ep_pipe = 0;
 			}
 
-			info->sync_ep_pipe = 0;
+			disable_audio_stream(subs);
+			guard(mutex)(&chip->mutex);
+			subs->opened = 0;
 		}
-
-		disable_audio_stream(subs);
-		guard(mutex)(&chip->mutex);
-		subs->opened = 0;
 	}
 
 response:
-- 
2.53.0.473.g4a7958ca14-goog