linux-kernel - [PATCH v14 3/4] xhci: sideband: add api to trace sideband usage

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Message-ID: <20250604082449.2029156-4-guanyulin@google.com>
Date: Wed,  4 Jun 2025 08:23:09 +0000
From: Guan-Yu Lin <guanyulin@...gle.com>
To: gregkh@...uxfoundation.org, mathias.nyman@...el.com, gargaditya08@...e.com, 
	kekrby@...il.com, jeff.johnson@....qualcomm.com, quic_zijuhu@...cinc.com, 
	andriy.shevchenko@...ux.intel.com, ben@...adent.org.uk, broonie@...nel.org, 
	quic_wcheng@...cinc.com, krzysztof.kozlowski@...aro.org, 
	sumit.garg@...nel.org
Cc: linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Guan-Yu Lin <guanyulin@...gle.com>
Subject: [PATCH v14 3/4] xhci: sideband: add api to trace sideband usage

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@...gle.com>
---
 drivers/usb/host/Kconfig          | 11 +++++++++
 drivers/usb/host/xhci-sideband.c  | 38 +++++++++++++++++++++++++++++++
 include/linux/usb/xhci-sideband.h |  9 ++++++++
 3 files changed, 58 insertions(+)

diff --git a/drivers/usb/host/Kconfig b/drivers/usb/host/Kconfig
index 109100cc77a3..49b9cdc11298 100644
--- a/drivers/usb/host/Kconfig
+++ b/drivers/usb/host/Kconfig
@@ -113,6 +113,17 @@ config USB_XHCI_SIDEBAND
 	  xHCI USB endpoints directly, allowing CPU to sleep while playing
 	  audio.
 
+config USB_XHCI_SIDEBAND_SUSPEND
+	  bool "xHCI support for sideband during system suspend"
+	  depends on USB_XHCI_SIDEBAND
+	  depends on USB_XHCI_PLATFORM
+	  depends on SUSPEND
+	  help
+	    Say 'Y' to enable the support for the xHCI sideband capability
+	    after system suspended. In addition to USB_XHCI_SIDEBAND, this
+	    config allows endpoints and interrupters associated with the
+	    sideband function when system is suspended.
+
 config USB_XHCI_TEGRA
 	tristate "xHCI support for NVIDIA Tegra SoCs"
 	depends on PHY_TEGRA_XUSB
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);
-- 
2.49.0.1204.g71687c7c1d-goog