[PATCH v9 4/5] xhci: sideband: add api to trace sideband usage

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

The existing sideband driver only registers sidebands without tracking
their active usage. To address this, new apis are introduced to:
- mark sideband usage: record the sideband usage information in the USB
  device driver.
- query sideband status: provide a means for other drivers 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  | 82 +++++++++++++++++++++++++++++++
 include/linux/usb/xhci-sideband.h |  6 +++
 2 files changed, 88 insertions(+)

diff --git a/drivers/usb/host/xhci-sideband.c b/drivers/usb/host/xhci-sideband.c
index ffa6f1b825ff..d4931315dcf4 100644
--- a/drivers/usb/host/xhci-sideband.c
+++ b/drivers/usb/host/xhci-sideband.c
@@ -358,6 +358,88 @@ xhci_sideband_interrupter_id(struct xhci_sideband *sb)
 }
 EXPORT_SYMBOL_GPL(xhci_sideband_interrupter_id);
 
+/**
+ * xhci_sideband_get - record a new active sideband instance
+ * @sb: sideband instance for this usb device
+ *
+ * An active sideband indicates that another entity is currently using the host
+ * controller. Inform the usb_device associated with this sideband instance via
+ * usb_offload_get(). This allows the corresponding drivers to dynamically
+ * adjust power management actions based on current sideband activities.
+ *
+ * Returns 0 on success, negative error otherwise.
+ */
+int xhci_sideband_get(struct xhci_sideband *sb)
+{
+	struct usb_device *udev;
+	struct usb_hcd *hcd;
+	int ret = 0;
+
+	if (!sb || !sb->xhci)
+		return -ENODEV;
+
+	hcd = xhci_to_hcd(sb->xhci);
+	udev = sb->vdev->udev;
+	device_lock(&udev->dev);
+	ret = usb_offload_get(udev);
+	device_unlock(&udev->dev);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(xhci_sideband_get);
+
+/**
+ * xhci_sideband_put - record a deactivated sideband instance
+ * @sb: sideband instance for this usb device
+ *
+ * The inverse operation of xhci_sideband_get, which informs the associated
+ * usb_device via usb_offload_put(). This allows the corresponding drivers to
+ * dynamically adjust power management actions based on sideband activities.
+ *
+ * Returns 0 on success, negative error otherwise.
+ */
+int xhci_sideband_put(struct xhci_sideband *sb)
+{
+	struct usb_device *udev;
+	struct usb_hcd *hcd;
+	int ret = 0;
+
+	if (!sb || !sb->xhci)
+		return -ENODEV;
+
+	hcd = xhci_to_hcd(sb->xhci);
+	udev = sb->vdev->udev;
+	device_lock(&udev->dev);
+	ret = usb_offload_put(udev);
+	device_unlock(&udev->dev);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(xhci_sideband_put);
+
+/**
+ * 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.
+ *
+ * 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;
+
+	device_lock(&udev->dev);
+	active = usb_offload_check(udev);
+	device_unlock(&udev->dev);
+
+	return active;
+}
+EXPORT_SYMBOL_GPL(xhci_sideband_check);
+
 /**
  * xhci_sideband_register - register a sideband for a usb device
  * @intf: usb interface associated with the sideband device
diff --git a/include/linux/usb/xhci-sideband.h b/include/linux/usb/xhci-sideband.h
index 72aa17eb068d..6de1d9c161a1 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 */
 
@@ -82,6 +83,11 @@ 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);
+
+int xhci_sideband_get(struct xhci_sideband *sb);
+int xhci_sideband_put(struct xhci_sideband *sb);
+bool xhci_sideband_check(struct usb_hcd *hcd);
+
 int
 xhci_sideband_create_interrupter(struct xhci_sideband *sb, int num_seg,
 				 bool ip_autoclear, u32 imod_interval, int intr_num);
-- 
2.48.0.rc2.279.g1de40edade-goog