[PATCH v3 1/2] usb: core: use dedicated spinlock for offload state

[PATCH v3 1/2] usb: core: use dedicated spinlock for offload state

[Guan-Yu Lin]

Replace the coarse USB device lock with a dedicated offload_lock
spinlock to reduce contention during offload operations. Use
offload_pm_locked to synchronize with PM transitions and replace
the legacy offload_at_suspend flag.

Optimize usb_offload_get/put by switching from auto-resume/suspend
to pm_runtime_get_if_active(). This ensures offload state is only
modified when the device is already active, avoiding unnecessary
power transitions.

Cc: stable@vger.kernel.org
Fixes: ef82a4803aab ("xhci: sideband: add api to trace sideband usage")
Signed-off-by: Guan-Yu Lin <guanyulin@google.com>
---
 drivers/usb/core/driver.c        |  23 ++++---
 drivers/usb/core/offload.c       | 107 ++++++++++++++++++-------------
 drivers/usb/core/usb.c           |   1 +
 drivers/usb/host/xhci-sideband.c |   4 +-
 include/linux/usb.h              |  10 ++-
 5 files changed, 89 insertions(+), 56 deletions(-)

diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index d29edc7c616a..74b8bdc27dbf 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -1415,14 +1415,16 @@ static int usb_suspend_both(struct usb_device *udev, pm_message_t msg)
 	int			status = 0;
 	int			i = 0, n = 0;
 	struct usb_interface	*intf;
+	bool			offload_active = false;
 
 	if (udev->state == USB_STATE_NOTATTACHED ||
 			udev->state == USB_STATE_SUSPENDED)
 		goto done;
 
+	usb_offload_set_pm_locked(udev, true);
 	if (msg.event == PM_EVENT_SUSPEND && usb_offload_check(udev)) {
 		dev_dbg(&udev->dev, "device offloaded, skip suspend.\n");
-		udev->offload_at_suspend = 1;
+		offload_active = true;
 	}
 
 	/* Suspend all the interfaces and then udev itself */
@@ -1436,8 +1438,7 @@ static int usb_suspend_both(struct usb_device *udev, pm_message_t msg)
 			 * interrupt urbs, allowing interrupt events to be
 			 * handled during system suspend.
 			 */
-			if (udev->offload_at_suspend &&
-			    intf->needs_remote_wakeup) {
+			if (offload_active && intf->needs_remote_wakeup) {
 				dev_dbg(&intf->dev,
 					"device offloaded, skip suspend.\n");
 				continue;
@@ -1452,7 +1453,7 @@ static int usb_suspend_both(struct usb_device *udev, pm_message_t msg)
 		}
 	}
 	if (status == 0) {
-		if (!udev->offload_at_suspend)
+		if (!offload_active)
 			status = usb_suspend_device(udev, msg);
 
 		/*
@@ -1498,7 +1499,7 @@ static int usb_suspend_both(struct usb_device *udev, pm_message_t msg)
 	 */
 	} else {
 		udev->can_submit = 0;
-		if (!udev->offload_at_suspend) {
+		if (!offload_active) {
 			for (i = 0; i < 16; ++i) {
 				usb_hcd_flush_endpoint(udev, udev->ep_out[i]);
 				usb_hcd_flush_endpoint(udev, udev->ep_in[i]);
@@ -1507,6 +1508,8 @@ static int usb_suspend_both(struct usb_device *udev, pm_message_t msg)
 	}
 
  done:
+	if (status != 0)
+		usb_offload_set_pm_locked(udev, false);
 	dev_vdbg(&udev->dev, "%s: status %d\n", __func__, status);
 	return status;
 }
@@ -1536,16 +1539,19 @@ static int usb_resume_both(struct usb_device *udev, pm_message_t msg)
 	int			status = 0;
 	int			i;
 	struct usb_interface	*intf;
+	bool			offload_active = false;
 
 	if (udev->state == USB_STATE_NOTATTACHED) {
 		status = -ENODEV;
 		goto done;
 	}
 	udev->can_submit = 1;
+	if (msg.event == PM_EVENT_RESUME)
+		offload_active = usb_offload_check(udev);
 
 	/* Resume the device */
 	if (udev->state == USB_STATE_SUSPENDED || udev->reset_resume) {
-		if (!udev->offload_at_suspend)
+		if (!offload_active)
 			status = usb_resume_device(udev, msg);
 		else
 			dev_dbg(&udev->dev,
@@ -1562,8 +1568,7 @@ static int usb_resume_both(struct usb_device *udev, pm_message_t msg)
 			 * pending interrupt urbs, allowing interrupt events
 			 * to be handled during system suspend.
 			 */
-			if (udev->offload_at_suspend &&
-			    intf->needs_remote_wakeup) {
+			if (offload_active && intf->needs_remote_wakeup) {
 				dev_dbg(&intf->dev,
 					"device offloaded, skip resume.\n");
 				continue;
@@ -1572,11 +1577,11 @@ static int usb_resume_both(struct usb_device *udev, pm_message_t msg)
 					udev->reset_resume);
 		}
 	}
-	udev->offload_at_suspend = 0;
 	usb_mark_last_busy(udev);
 
  done:
 	dev_vdbg(&udev->dev, "%s: status %d\n", __func__, status);
+	usb_offload_set_pm_locked(udev, false);
 	if (!status)
 		udev->reset_resume = 0;
 	return status;
diff --git a/drivers/usb/core/offload.c b/drivers/usb/core/offload.c
index 7c699f1b8d2b..c24945294d7e 100644
--- a/drivers/usb/core/offload.c
+++ b/drivers/usb/core/offload.c
@@ -25,33 +25,30 @@
  */
 int usb_offload_get(struct usb_device *udev)
 {
-	int ret;
+	int ret = 0;
 
-	usb_lock_device(udev);
-	if (udev->state == USB_STATE_NOTATTACHED) {
-		usb_unlock_device(udev);
+	if (!usb_get_dev(udev))
 		return -ENODEV;
-	}
 
-	if (udev->state == USB_STATE_SUSPENDED ||
-		   udev->offload_at_suspend) {
-		usb_unlock_device(udev);
-		return -EBUSY;
+	if (pm_runtime_get_if_active(&udev->dev) != 1) {
+		ret = -EBUSY;
+		goto err_rpm;
 	}
 
-	/*
-	 * offload_usage could only be modified when the device is active, since
-	 * it will alter the suspend flow of the device.
-	 */
-	ret = usb_autoresume_device(udev);
-	if (ret < 0) {
-		usb_unlock_device(udev);
-		return ret;
+	spin_lock(&udev->offload_lock);
+
+	if (udev->offload_pm_locked) {
+		ret = -EAGAIN;
+		goto err;
 	}
 
 	udev->offload_usage++;
-	usb_autosuspend_device(udev);
-	usb_unlock_device(udev);
+
+err:
+	spin_unlock(&udev->offload_lock);
+	pm_runtime_put_autosuspend(&udev->dev);
+err_rpm:
+	usb_put_dev(udev);
 
 	return ret;
 }
@@ -69,35 +66,32 @@ EXPORT_SYMBOL_GPL(usb_offload_get);
  */
 int usb_offload_put(struct usb_device *udev)
 {
-	int ret;
+	int ret = 0;
 
-	usb_lock_device(udev);
-	if (udev->state == USB_STATE_NOTATTACHED) {
-		usb_unlock_device(udev);
+	if (!usb_get_dev(udev))
 		return -ENODEV;
-	}
 
-	if (udev->state == USB_STATE_SUSPENDED ||
-		   udev->offload_at_suspend) {
-		usb_unlock_device(udev);
-		return -EBUSY;
+	if (pm_runtime_get_if_active(&udev->dev) != 1) {
+		ret = -EBUSY;
+		goto err_rpm;
 	}
 
-	/*
-	 * offload_usage could only be modified when the device is active, since
-	 * it will alter the suspend flow of the device.
-	 */
-	ret = usb_autoresume_device(udev);
-	if (ret < 0) {
-		usb_unlock_device(udev);
-		return ret;
+	spin_lock(&udev->offload_lock);
+
+	if (udev->offload_pm_locked) {
+		ret = -EAGAIN;
+		goto err;
 	}
 
 	/* Drop the count when it wasn't 0, ignore the operation otherwise. */
 	if (udev->offload_usage)
 		udev->offload_usage--;
-	usb_autosuspend_device(udev);
-	usb_unlock_device(udev);
+
+err:
+	spin_unlock(&udev->offload_lock);
+	pm_runtime_put_autosuspend(&udev->dev);
+err_rpm:
+	usb_put_dev(udev);
 
 	return ret;
 }
@@ -112,25 +106,52 @@ EXPORT_SYMBOL_GPL(usb_offload_put);
  * management.
  *
  * The caller must hold @udev's device lock. In addition, the caller should
- * ensure downstream usb devices are all either suspended or marked as
- * "offload_at_suspend" to ensure the correctness of the return value.
+ * ensure downstream usb devices are all marked as "offload_pm_locked" to
+ * ensure the correctness of the return value.
  *
  * Returns true on any offload activity, false otherwise.
  */
 bool usb_offload_check(struct usb_device *udev) __must_hold(&udev->dev->mutex)
 {
 	struct usb_device *child;
-	bool active;
+	bool active = false;
 	int port1;
 
+	spin_lock(&udev->offload_lock);
+	if (udev->offload_usage)
+		active = true;
+	spin_unlock(&udev->offload_lock);
+
+	if (active)
+		return true;
+
 	usb_hub_for_each_child(udev, port1, child) {
 		usb_lock_device(child);
 		active = usb_offload_check(child);
 		usb_unlock_device(child);
+
 		if (active)
-			return true;
+			break;
 	}
 
-	return !!udev->offload_usage;
+	return active;
 }
 EXPORT_SYMBOL_GPL(usb_offload_check);
+
+/**
+ * usb_offload_set_pm_locked - set the PM lock state of a USB device
+ * @udev: the USB device to modify
+ * @locked: the new lock state
+ *
+ * Setting @locked to true prevents offload_usage from being modified. This
+ * ensures that offload activities cannot be started or stopped during critical
+ * power management transitions, maintaining a stable state for the duration
+ * of the transition.
+ */
+void usb_offload_set_pm_locked(struct usb_device *udev, bool locked)
+{
+	spin_lock(&udev->offload_lock);
+	udev->offload_pm_locked = locked;
+	spin_unlock(&udev->offload_lock);
+}
+EXPORT_SYMBOL_GPL(usb_offload_set_pm_locked);
diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index e740f7852bcd..8f7ca084010f 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -671,6 +671,7 @@ struct usb_device *usb_alloc_dev(struct usb_device *parent,
 	set_dev_node(&dev->dev, dev_to_node(bus->sysdev));
 	dev->state = USB_STATE_ATTACHED;
 	dev->lpm_disable_count = 1;
+	spin_lock_init(&dev->offload_lock);
 	dev->offload_usage = 0;
 	atomic_set(&dev->urbnum, 0);
 
diff --git a/drivers/usb/host/xhci-sideband.c b/drivers/usb/host/xhci-sideband.c
index 2bd77255032b..1ddb64b0a48e 100644
--- a/drivers/usb/host/xhci-sideband.c
+++ b/drivers/usb/host/xhci-sideband.c
@@ -291,8 +291,8 @@ EXPORT_SYMBOL_GPL(xhci_sideband_get_event_buffer);
  * Allow other drivers, such as usb controller driver, to check if there are
  * any sideband activity on the host controller. This information could be used
  * for power management or other forms of resource management. The caller should
- * ensure downstream usb devices are all either suspended or marked as
- * "offload_at_suspend" to ensure the correctness of the return value.
+ * ensure downstream usb devices are all marked as "offload_pm_locked" to ensure
+ * the correctness of the return value.
  *
  * Returns true on any active sideband existence, false otherwise.
  */
diff --git a/include/linux/usb.h b/include/linux/usb.h
index fbfcc70b07fb..a4b031196da3 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -21,6 +21,7 @@
 #include <linux/completion.h>	/* for struct completion */
 #include <linux/sched.h>	/* for current && schedule_timeout */
 #include <linux/mutex.h>	/* for struct mutex */
+#include <linux/spinlock.h>	/* for spinlock_t */
 #include <linux/pm_runtime.h>	/* for runtime PM */
 
 struct usb_device;
@@ -636,8 +637,9 @@ struct usb3_lpm_parameters {
  * @do_remote_wakeup:  remote wakeup should be enabled
  * @reset_resume: needs reset instead of resume
  * @port_is_suspended: the upstream port is suspended (L2 or U3)
- * @offload_at_suspend: offload activities during suspend is enabled.
+ * @offload_pm_locked: prevents offload_usage changes during PM transitions.
  * @offload_usage: number of offload activities happening on this usb device.
+ * @offload_lock: protects offload_usage and offload_pm_locked
  * @slot_id: Slot ID assigned by xHCI
  * @l1_params: best effor service latency for USB2 L1 LPM state, and L1 timeout.
  * @u1_params: exit latencies for USB3 U1 LPM state, and hub-initiated timeout.
@@ -726,8 +728,9 @@ struct usb_device {
 	unsigned do_remote_wakeup:1;
 	unsigned reset_resume:1;
 	unsigned port_is_suspended:1;
-	unsigned offload_at_suspend:1;
+	unsigned offload_pm_locked:1;
 	int offload_usage;
+	spinlock_t offload_lock;
 	enum usb_link_tunnel_mode tunnel_mode;
 	struct device_link *usb4_link;
 
@@ -849,6 +852,7 @@ static inline void usb_mark_last_busy(struct usb_device *udev)
 int usb_offload_get(struct usb_device *udev);
 int usb_offload_put(struct usb_device *udev);
 bool usb_offload_check(struct usb_device *udev);
+void usb_offload_set_pm_locked(struct usb_device *udev, bool locked);
 #else
 
 static inline int usb_offload_get(struct usb_device *udev)
@@ -857,6 +861,8 @@ static inline int usb_offload_put(struct usb_device *udev)
 { return 0; }
 static inline bool usb_offload_check(struct usb_device *udev)
 { return false; }
+static inline void usb_offload_set_pm_locked(struct usb_device *udev, bool locked)
+{ }
 #endif
 
 extern int usb_disable_lpm(struct usb_device *udev);
-- 
2.53.0.1018.g2bb0e51243-goog

[PATCH v3 2/2] usb: host: xhci-sideband: delegate offload_usage tracking to class drivers

[Guan-Yu Lin]

Remove usb_offload_get() and usb_offload_put() from the xHCI sideband
interrupter creation and removal paths.

The responsibility of manipulating offload_usage now lies entirely with
the USB class drivers. They have the precise context of when an offload
data stream actually starts and stops, ensuring a much more accurate
representation of offload activity for power management.

Cc: stable@vger.kernel.org
Fixes: ef82a4803aab ("xhci: sideband: add api to trace sideband usage")
Signed-off-by: Guan-Yu Lin <guanyulin@google.com>
---
 drivers/usb/host/xhci-sideband.c  | 14 +-------------
 sound/usb/qcom/qc_audio_offload.c | 10 +++++++++-
 2 files changed, 10 insertions(+), 14 deletions(-)

diff --git a/drivers/usb/host/xhci-sideband.c b/drivers/usb/host/xhci-sideband.c
index 1ddb64b0a48e..651973606137 100644
--- a/drivers/usb/host/xhci-sideband.c
+++ b/drivers/usb/host/xhci-sideband.c
@@ -93,8 +93,6 @@ __xhci_sideband_remove_endpoint(struct xhci_sideband *sb, struct xhci_virt_ep *e
 static void
 __xhci_sideband_remove_interrupter(struct xhci_sideband *sb)
 {
-	struct usb_device *udev;
-
 	lockdep_assert_held(&sb->mutex);
 
 	if (!sb->ir)
@@ -102,10 +100,6 @@ __xhci_sideband_remove_interrupter(struct xhci_sideband *sb)
 
 	xhci_remove_secondary_interrupter(xhci_to_hcd(sb->xhci), sb->ir);
 	sb->ir = NULL;
-	udev = sb->vdev->udev;
-
-	if (udev->state != USB_STATE_NOTATTACHED)
-		usb_offload_put(udev);
 }
 
 /* sideband api functions */
@@ -328,9 +322,6 @@ int
 xhci_sideband_create_interrupter(struct xhci_sideband *sb, int num_seg,
 				 bool ip_autoclear, u32 imod_interval, int intr_num)
 {
-	int ret = 0;
-	struct usb_device *udev;
-
 	if (!sb || !sb->xhci)
 		return -ENODEV;
 
@@ -348,12 +339,9 @@ xhci_sideband_create_interrupter(struct xhci_sideband *sb, int num_seg,
 	if (!sb->ir)
 		return -ENOMEM;
 
-	udev = sb->vdev->udev;
-	ret = usb_offload_get(udev);
-
 	sb->ir->ip_autoclear = ip_autoclear;
 
-	return ret;
+	return 0;
 }
 EXPORT_SYMBOL_GPL(xhci_sideband_create_interrupter);
 
diff --git a/sound/usb/qcom/qc_audio_offload.c b/sound/usb/qcom/qc_audio_offload.c
index cfb30a195364..abafbc78dea9 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);
 	}
 }
 
@@ -1182,12 +1183,16 @@ static int uaudio_event_ring_setup(struct snd_usb_substream *subs,
 	dma_coherent = dev_is_dma_coherent(subs->dev->bus->sysdev);
 	er_pa = 0;
 
+	ret = usb_offload_get(subs->dev);
+	if (ret < 0)
+		goto exit;
+
 	/* event ring */
 	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 +1224,8 @@ 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 +1490,7 @@ 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,
-- 
2.53.0.1018.g2bb0e51243-goog

Re: [PATCH v3 1/2] usb: core: use dedicated spinlock for offload state

[Mathias Nyman]

Hi

On 3/24/26 22:38, Guan-Yu Lin wrote:
> Replace the coarse USB device lock with a dedicated offload_lock
> spinlock to reduce contention during offload operations. Use
> offload_pm_locked to synchronize with PM transitions and replace
> the legacy offload_at_suspend flag.
> 
> Optimize usb_offload_get/put by switching from auto-resume/suspend
> to pm_runtime_get_if_active(). This ensures offload state is only
> modified when the device is already active, avoiding unnecessary
> power transitions.
> 
> Cc: stable@vger.kernel.org
> Fixes: ef82a4803aab ("xhci: sideband: add api to trace sideband usage")
> Signed-off-by: Guan-Yu Lin <guanyulin@google.com>
> ---

> diff --git a/drivers/usb/core/offload.c b/drivers/usb/core/offload.c
> index 7c699f1b8d2b..c24945294d7e 100644
> --- a/drivers/usb/core/offload.c
> +++ b/drivers/usb/core/offload.c
> @@ -25,33 +25,30 @@
>    */
>   int usb_offload_get(struct usb_device *udev)
>   {
> -	int ret;
> +	int ret = 0;
>   
> -	usb_lock_device(udev);
> -	if (udev->state == USB_STATE_NOTATTACHED) {
> -		usb_unlock_device(udev);
> +	if (!usb_get_dev(udev))
>   		return -ENODEV;
> -	}
>   
> -	if (udev->state == USB_STATE_SUSPENDED ||
> -		   udev->offload_at_suspend) {
> -		usb_unlock_device(udev);
> -		return -EBUSY;
> +	if (pm_runtime_get_if_active(&udev->dev) != 1) {
> +		ret = -EBUSY;
> +		goto err_rpm;
>   	}
>   
> -	/*
> -	 * offload_usage could only be modified when the device is active, since
> -	 * it will alter the suspend flow of the device.
> -	 */
> -	ret = usb_autoresume_device(udev);
> -	if (ret < 0) {
> -		usb_unlock_device(udev);
> -		return ret;
> +	spin_lock(&udev->offload_lock);
> +
> +	if (udev->offload_pm_locked) {

Could we get rid of 'udev->offload_pm_locked' and 'usb_offload_set_pm_locked()'
by calling a synchronous pm_runtime_get_sync() or pm_runtime_resume_and_get()?

This way we can ensure udev->offload_usage isn't modified mid runtime suspend or
resume as resume is guaranteed to have finished and suspend won't be called,
at least not for the runtime case.

> +		ret = -EAGAIN;
> +		goto err;
>   	}
>   
>   	udev->offload_usage++;
> -	usb_autosuspend_device(udev);
> -	usb_unlock_device(udev);
> +
> +err:
> +	spin_unlock(&udev->offload_lock);
> +	pm_runtime_put_autosuspend(&udev->dev);
> +err_rpm:
> +	usb_put_dev(udev);
>   
>   	return ret;
>   }
> @@ -69,35 +66,32 @@ EXPORT_SYMBOL_GPL(usb_offload_get);
>    */
>   int usb_offload_put(struct usb_device *udev)
>   {
> -	int ret;
> +	int ret = 0;
>   
> -	usb_lock_device(udev);
> -	if (udev->state == USB_STATE_NOTATTACHED) {
> -		usb_unlock_device(udev);
> +	if (!usb_get_dev(udev))
>   		return -ENODEV;
> -	}
>   
> -	if (udev->state == USB_STATE_SUSPENDED ||
> -		   udev->offload_at_suspend) {
> -		usb_unlock_device(udev);
> -		return -EBUSY;
> +	if (pm_runtime_get_if_active(&udev->dev) != 1) {
> +		ret = -EBUSY;
> +		goto err_rpm;
>   	}
>   
> -	/*
> -	 * offload_usage could only be modified when the device is active, since
> -	 * it will alter the suspend flow of the device.
> -	 */
> -	ret = usb_autoresume_device(udev);
> -	if (ret < 0) {
> -		usb_unlock_device(udev);
> -		return ret;
> +	spin_lock(&udev->offload_lock);
> +
> +	if (udev->offload_pm_locked) {
> +		ret = -EAGAIN;
> +		goto err;


Ending up here is about unlucky timing, i.e. usb_offload_put() is called while
device is pretending to suspend/resume. Result here is that udev->offload_usage is
not decremented, and usb device won't properly suspend anymore even if device is
no longer offloaded.


>   	}
>   
>   	/* Drop the count when it wasn't 0, ignore the operation otherwise. */
>   	if (udev->offload_usage)
>   		udev->offload_usage--;
> -	usb_autosuspend_device(udev);
> -	usb_unlock_device(udev);
> +
> +err:
> +	spin_unlock(&udev->offload_lock);
> +	pm_runtime_put_autosuspend(&udev->dev);
> +err_rpm:
> +	usb_put_dev(udev);
>   
>   	return ret;
>   }
> @@ -112,25 +106,52 @@ EXPORT_SYMBOL_GPL(usb_offload_put);
>    * management.
>    *
>    * The caller must hold @udev's device lock. In addition, the caller should
> - * ensure downstream usb devices are all either suspended or marked as
> - * "offload_at_suspend" to ensure the correctness of the return value.
> + * ensure downstream usb devices are all marked as "offload_pm_locked" to
> + * ensure the correctness of the return value.
>    *
>    * Returns true on any offload activity, false otherwise.
>    */
>   bool usb_offload_check(struct usb_device *udev) __must_hold(&udev->dev->mutex)
>   {
>   	struct usb_device *child;
> -	bool active;
> +	bool active = false;
>   	int port1;
>   
> +	spin_lock(&udev->offload_lock);
> +	if (udev->offload_usage)
> +		active = true;
> +	spin_unlock(&udev->offload_lock);
> +> +	if (active)
> +		return true;

Not sure what the purpose of the spinlock is above

> +
>   	usb_hub_for_each_child(udev, port1, child) {
>   		usb_lock_device(child);
>   		active = usb_offload_check(child);
>   		usb_unlock_device(child);
> +
>   		if (active)
> -			return true;
> +			break;
>   	}
>   
> -	return !!udev->offload_usage;
> +	return active;
>   }
>   EXPORT_SYMBOL_GPL(usb_offload_check);
> +
> +/**
> + * usb_offload_set_pm_locked - set the PM lock state of a USB device
> + * @udev: the USB device to modify
> + * @locked: the new lock state
> + *
> + * Setting @locked to true prevents offload_usage from being modified. This
> + * ensures that offload activities cannot be started or stopped during critical
> + * power management transitions, maintaining a stable state for the duration
> + * of the transition.
> + */
> +void usb_offload_set_pm_locked(struct usb_device *udev, bool locked)
> +{
> +	spin_lock(&udev->offload_lock);
> +	udev->offload_pm_locked = locked;
> +	spin_unlock(&udev->offload_lock);
> 

spinlock usage unclear here as well

Thanks
Mathias