[PATCH v13 3/4] xhci: sideband: add api to trace sideband usage

Guan-Yu Lin
2025-05-28T09:09:20Z

The existing sideband driver only registers sidebands without tracking
their active usage. To address this, sideband will now record its active
usage when it creates/removes interrupters. In addition, a new api is
introduced to provide a means for other dirvers to fetch sideband
activity information on a USB host controller.

Signed-off-by: Guan-Yu Lin <guanyulin@google.com>
---
drivers/usb/host/xhci-sideband.c | 38 +++++++++++++++++++++++++++++++
include/linux/usb/xhci-sideband.h | 9 ++++++++
2 files changed, 47 insertions(+)

diff --git a/drivers/usb/host/xhci-sideband.c b/drivers/usb/host/xhci-sideband.c
index d49f9886dd84..15d72c23c0e0 100644
--- a/drivers/usb/host/xhci-sideband.c
+++ b/drivers/usb/host/xhci-sideband.c
@@ -266,6 +266,33 @@ xhci_sideband_get_event_buffer(struct xhci_sideband *sb)
}
EXPORT_SYMBOL_GPL(xhci_sideband_get_event_buffer);

+#if IS_ENABLED(CONFIG_USB_XHCI_SIDEBAND_SUSPEND)
+/**
+ * xhci_sideband_check - check the existence of active sidebands
+ * @hcd: the host controller driver associated with the target host controller
+ *
+ * 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.
+ *
+ * Returns true on any active sideband existence, false otherwise.
+ */
+bool xhci_sideband_check(struct usb_hcd *hcd)
+{
+ struct usb_device *udev = hcd->self.root_hub;
+ bool active;
+
+ usb_lock_device(udev);
+ active = usb_offload_check(udev);
+ usb_unlock_device(udev);
+
+ return active;
+}
+EXPORT_SYMBOL_GPL(xhci_sideband_check);
+#endif /* IS_ENABLED(CONFIG_USB_XHCI_SIDEBAND_SUSPEND) */
+
/**
* xhci_sideband_create_interrupter - creates a new interrupter for this sideband
* @sb: sideband instance for this usb device
@@ -286,6 +313,7 @@ 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;
@@ -304,6 +332,9 @@ xhci_sideband_create_interrupter(struct xhci_sideband *sb, int num_seg,
goto out;
}

+ udev = sb->vdev->udev;
+ ret = usb_offload_get(udev);
+
sb->ir->ip_autoclear = ip_autoclear;

out:
@@ -323,6 +354,8 @@ EXPORT_SYMBOL_GPL(xhci_sideband_create_interrupter);
void
xhci_sideband_remove_interrupter(struct xhci_sideband *sb)
{
+ struct usb_device *udev;
+
if (!sb || !sb->ir)
return;

@@ -330,6 +363,11 @@ 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);
+
mutex_unlock(&sb->mutex);
}
EXPORT_SYMBOL_GPL(xhci_sideband_remove_interrupter);
diff --git a/include/linux/usb/xhci-sideband.h b/include/linux/usb/xhci-sideband.h
index 45288c392f6e..5174cc5afc98 100644
--- a/include/linux/usb/xhci-sideband.h
+++ b/include/linux/usb/xhci-sideband.h
@@ -11,6 +11,7 @@

#include <linux/scatterlist.h>
#include <linux/usb.h>
+#include <linux/usb/hcd.h>

#define EP_CTX_PER_DEV 31 /* FIXME defined twice, from xhci.h */

@@ -83,6 +84,14 @@ xhci_sideband_get_endpoint_buffer(struct xhci_sideband *sb,
struct usb_host_endpoint *host_ep);
struct sg_table *
xhci_sideband_get_event_buffer(struct xhci_sideband *sb);
+
+#if IS_ENABLED(CONFIG_USB_XHCI_SIDEBAND_SUSPEND)
+bool xhci_sideband_check(struct usb_hcd *hcd);
+#else
+static inline bool xhci_sideband_check(struct usb_hcd *hcd)
+{ return false; }
+#endif /* IS_ENABLED(CONFIG_USB_XHCI_SIDEBAND_SUSPEND) */
+
int
xhci_sideband_create_interrupter(struct xhci_sideband *sb, int num_seg,
bool ip_autoclear, u32 imod_interval, int intr_num);
--
2.49.0.1164.gab81da1b16-goog