linux-kernel - [PATCH v2 3/4] usb: dwc3: qcom: Facilitate autosuspend during host mode

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Message-Id: <20250610091357.2983085-4-krishna.kurapati@oss.qualcomm.com>
Date: Tue, 10 Jun 2025 14:43:56 +0530
From: Krishna Kurapati <krishna.kurapati@....qualcomm.com>
To: Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bjorn Andersson <bjorn.andersson@....qualcomm.com>
Cc: linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Krishna Kurapati <krishna.kurapati@....qualcomm.com>
Subject: [PATCH v2 3/4] usb: dwc3: qcom: Facilitate autosuspend during host mode

When in host mode, it is intended that the controller goes to suspend
state to save power and wait for interrupts from connected peripheral
to wake it up. This is particularly used in cases where a HID or Audio
device is connected. In such scenarios, the usb controller can enter
auto suspend and resume action after getting interrupts from the
connected device.

Allow autosuspend for and xhci device and allow userspace to decide
whether to enable this functionality.

a) Register to usb-core notifications in set_role vendor callback to
identify when root hubs are being created. Configure them to
use_autosuspend.

b) Identify usb core notifications where the HCD is being added and
enable autosuspend for that particular xhci device.

Signed-off-by: Krishna Kurapati <krishna.kurapati@....qualcomm.com>
---
 drivers/usb/dwc3/dwc3-qcom.c | 62 ++++++++++++++++++++++++++++++++----
 1 file changed, 56 insertions(+), 6 deletions(-)

diff --git a/drivers/usb/dwc3/dwc3-qcom.c b/drivers/usb/dwc3/dwc3-qcom.c
index d40b52e2ba01..17bbd5a06c08 100644
--- a/drivers/usb/dwc3/dwc3-qcom.c
+++ b/drivers/usb/dwc3/dwc3-qcom.c
@@ -95,6 +95,8 @@ struct dwc3_qcom {
 	 * internally by mutex lock.
 	 */
 	enum usb_role		current_role;
+
+	struct notifier_block	xhci_nb;
 };
 
 #define to_dwc3_qcom(d) container_of((d), struct dwc3_qcom, dwc)
@@ -647,6 +649,39 @@ static int dwc3_qcom_setup_irq(struct dwc3_qcom *qcom, struct platform_device *p
 	return 0;
 }
 
+static int dwc3_xhci_event_notifier(struct notifier_block *nb,
+				    unsigned long event, void *ptr)
+{
+	struct dwc3_qcom  *qcom	= container_of(nb, struct dwc3_qcom, xhci_nb);
+	struct dwc3	  *dwc	= &qcom->dwc;
+	struct usb_bus	  *ubus	= ptr;
+	struct usb_hcd	  *hcd;
+
+	if (!dwc->xhci)
+		goto done;
+
+	hcd = platform_get_drvdata(dwc->xhci);
+	if (!hcd)
+		goto done;
+
+	if (event != USB_BUS_ADD)
+		goto done;
+
+	if (strcmp(dev_name(ubus->sysdev), dev_name(dwc->sysdev)) != 0)
+		goto done;
+
+	if (event == USB_BUS_ADD) {
+		/*
+		 * Identify instant of creation of primary hcd and
+		 * mark xhci as autosuspend capable at this point.
+		 */
+		pm_runtime_use_autosuspend(&dwc->xhci->dev);
+	}
+
+done:
+	return NOTIFY_DONE;
+}
+
 static void dwc3_qcom_set_role_notifier(struct dwc3 *dwc, enum usb_role next_role)
 {
 	struct dwc3_qcom *qcom = to_dwc3_qcom(dwc);
@@ -659,12 +694,22 @@ static void dwc3_qcom_set_role_notifier(struct dwc3 *dwc, enum usb_role next_rol
 		return;
 	}
 
-	if (qcom->current_role == USB_ROLE_DEVICE &&
-	    next_role != USB_ROLE_DEVICE)
+	if (qcom->current_role == USB_ROLE_NONE) {
+		if (next_role == USB_ROLE_DEVICE) {
+			dwc3_qcom_vbus_override_enable(qcom, true);
+		} else if (next_role == USB_ROLE_HOST) {
+			qcom->xhci_nb.notifier_call = dwc3_xhci_event_notifier;
+			usb_register_notify(&qcom->xhci_nb);
+		}
+	} else if (qcom->current_role == USB_ROLE_DEVICE &&
+		   next_role != USB_ROLE_DEVICE) {
 		dwc3_qcom_vbus_override_enable(qcom, false);
-	else if ((qcom->current_role != USB_ROLE_DEVICE) &&
-		 (next_role == USB_ROLE_DEVICE))
-		dwc3_qcom_vbus_override_enable(qcom, true);
+	} else if (qcom->current_role == USB_ROLE_HOST) {
+		if (next_role == USB_ROLE_NONE)
+			usb_unregister_notify(&qcom->xhci_nb);
+		else if (next_role == USB_ROLE_DEVICE)
+			dwc3_qcom_vbus_override_enable(qcom, true);
+	}
 
 	pm_runtime_mark_last_busy(qcom->dev);
 	pm_runtime_put_sync(qcom->dev);
@@ -774,6 +819,8 @@ static int dwc3_qcom_probe(struct platform_device *pdev)
 
 	if (qcom->mode == USB_DR_MODE_HOST) {
 		qcom->current_role = USB_ROLE_HOST;
+		qcom->xhci_nb.notifier_call = dwc3_xhci_event_notifier;
+		usb_register_notify(&qcom->xhci_nb);
 	} else if (qcom->mode == USB_DR_MODE_PERIPHERAL) {
 		qcom->current_role = USB_ROLE_DEVICE;
 		dwc3_qcom_vbus_override_enable(qcom, true);
@@ -794,7 +841,7 @@ static int dwc3_qcom_probe(struct platform_device *pdev)
 	ret = dwc3_core_probe(&probe_data);
 	if (ret)  {
 		ret = dev_err_probe(dev, ret, "failed to register DWC3 Core\n");
-		goto clk_disable;
+		goto unregister_notify;
 	}
 
 	ret = dwc3_qcom_interconnect_init(qcom);
@@ -817,6 +864,9 @@ static int dwc3_qcom_probe(struct platform_device *pdev)
 	dwc3_qcom_interconnect_exit(qcom);
 remove_core:
 	dwc3_core_remove(&qcom->dwc);
+unregister_notify:
+	if (qcom->mode == USB_DR_MODE_HOST)
+		usb_unregister_notify(&qcom->xhci_nb);
 clk_disable:
 	clk_bulk_disable_unprepare(qcom->num_clocks, qcom->clks);
 
-- 
2.34.1