[PATCH v6 5/5] usb: host: enable sideband transfer during system sleep

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

Sharing a USB controller with another entity via xhci-sideband driver
creates power management complexities. To prevent the USB controller
from being inadvertently deactivated while in use by the other entity, a
usage-count based mechanism is implemented. This allows the system to
manage power effectively, ensuring the controller remains available
whenever needed.

Signed-off-by: Guan-Yu Lin <guanyulin@google.com>
---
 drivers/usb/core/driver.c    | 10 ++++++++++
 drivers/usb/dwc3/core.c      | 20 ++++++++++++++++++++
 drivers/usb/dwc3/core.h      |  1 +
 drivers/usb/host/xhci-plat.c | 10 ++++++++++
 include/linux/usb/hcd.h      |  7 +++++++
 5 files changed, 48 insertions(+)

diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index e53cb4c267b3..e5bb26e6c71a 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -1583,6 +1583,11 @@ int usb_suspend(struct device *dev, pm_message_t msg)
 	struct usb_device	*udev = to_usb_device(dev);
 	int r;
 
+	if (msg.event == PM_EVENT_SUSPEND && usb_sideband_check(udev)) {
+		dev_dbg(dev, "device accessed via sideband\n");
+		return 0;
+	}
+
 	unbind_no_pm_drivers_interfaces(udev);
 
 	/* From now on we are sure all drivers support suspend/resume
@@ -1619,6 +1624,11 @@ int usb_resume(struct device *dev, pm_message_t msg)
 	struct usb_device	*udev = to_usb_device(dev);
 	int			status;
 
+	if (msg.event == PM_EVENT_RESUME && usb_sideband_check(udev)) {
+		dev_dbg(dev, "device accessed via sideband\n");
+		return 0;
+	}
+
 	/* For all calls, take the device back to full power and
 	 * tell the PM core in case it was autosuspended previously.
 	 * Unbind the interfaces that will need rebinding later,
diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 2fdafbcbe44c..d85c68d5eba4 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -2550,8 +2550,18 @@ static int dwc3_runtime_idle(struct device *dev)
 static int dwc3_suspend(struct device *dev)
 {
 	struct dwc3	*dwc = dev_get_drvdata(dev);
+	struct platform_device *xhci = dwc->xhci;
+	struct usb_hcd  *hcd;
 	int		ret;
 
+	if (xhci) {
+		hcd = dev_get_drvdata(&xhci->dev);
+		if (xhci_sideband_check(hcd)) {
+			dev_dbg(dev, "device accessed via sideband\n");
+			return 0;
+		}
+	}
+
 	ret = dwc3_suspend_common(dwc, PMSG_SUSPEND);
 	if (ret)
 		return ret;
@@ -2564,8 +2574,18 @@ static int dwc3_suspend(struct device *dev)
 static int dwc3_resume(struct device *dev)
 {
 	struct dwc3	*dwc = dev_get_drvdata(dev);
+	struct platform_device *xhci = dwc->xhci;
+	struct usb_hcd  *hcd;
 	int		ret;
 
+	if (xhci) {
+		hcd = dev_get_drvdata(&xhci->dev);
+		if (xhci_sideband_check(hcd)) {
+			dev_dbg(dev, "device accessed via sideband\n");
+			return 0;
+		}
+	}
+
 	pinctrl_pm_select_default_state(dev);
 
 	pm_runtime_disable(dev);
diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index 80047d0df179..a585e9d80e59 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -26,6 +26,7 @@
 #include <linux/usb/ch9.h>
 #include <linux/usb/gadget.h>
 #include <linux/usb/otg.h>
+#include <linux/usb/hcd.h>
 #include <linux/usb/role.h>
 #include <linux/ulpi/interface.h>
 
diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
index 6e49ef1908eb..5fdbdf0c7f1a 100644
--- a/drivers/usb/host/xhci-plat.c
+++ b/drivers/usb/host/xhci-plat.c
@@ -456,6 +456,11 @@ static int xhci_plat_suspend_common(struct device *dev, struct pm_message pmsg)
 	struct xhci_hcd	*xhci = hcd_to_xhci(hcd);
 	int ret;
 
+	if (pmsg.event == PM_EVENT_SUSPEND && xhci_sideband_check(hcd)) {
+		dev_dbg(dev, "device accessed via sideband\n");
+		return 0;
+	}
+
 	if (pm_runtime_suspended(dev))
 		pm_runtime_resume(dev);
 
@@ -499,6 +504,11 @@ static int xhci_plat_resume_common(struct device *dev, struct pm_message pmsg)
 	struct xhci_hcd	*xhci = hcd_to_xhci(hcd);
 	int ret;
 
+	if (pmsg.event == PM_EVENT_RESUME && xhci_sideband_check(hcd)) {
+		dev_dbg(dev, "device accessed via sideband\n");
+		return 0;
+	}
+
 	if (!device_may_wakeup(dev) && (xhci->quirks & XHCI_SUSPEND_RESUME_CLKS)) {
 		ret = clk_prepare_enable(xhci->clk);
 		if (ret)
diff --git a/include/linux/usb/hcd.h b/include/linux/usb/hcd.h
index 9867c178d188..b22d25ccdf7c 100644
--- a/include/linux/usb/hcd.h
+++ b/include/linux/usb/hcd.h
@@ -772,6 +772,13 @@ extern struct rw_semaphore ehci_cf_port_reset_rwsem;
 #define USB_EHCI_LOADED		2
 extern unsigned long usb_hcds_loaded;
 
+#if IS_ENABLED(CONFIG_USB_XHCI_SIDEBAND)
+extern bool xhci_sideband_check(struct usb_hcd *hcd);
+#else
+static inline bool xhci_sideband_check(struct usb_hcd *hcd)
+{ return false; }
+#endif
+
 #endif /* __KERNEL__ */
 
 #endif /* __USB_CORE_HCD_H */
-- 
2.47.0.199.ga7371fff76-goog