Bluetooth: btusb: Add out-of-band wakeup support

Some onboard BT chips (e.g. Marvell 8997) contain a wakeup pin that
can be connected to a gpio on the CPU side, and can be used to wakeup
the host out-of-band. This can be useful in situations where the
in-band wakeup is not possible or not preferable (e.g. the in-band
wakeup may require the USB host controller to remain active, and
hence consuming more system power during system sleep).

The oob gpio interrupt to be used for wakeup on the CPU side, is
read from the device tree node, (using standard interrupt descriptors).
A devcie tree binding document is also added for the driver. The
compatible string is in compliance with
Documentation/devicetree/bindings/usb/usb-device.txt

Signed-off-by: Rajat Jain <rajatja@google.com>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

Documentation/devicetree/bindings/net/btusb.txt

@@ -0,0 +1,40 @@
+Generic Bluetooth controller over USB (btusb driver)
+---------------------------------------------------
+
+Required properties:
+
+  - compatible : should comply with the format "usbVID,PID" specified in
+		 Documentation/devicetree/bindings/usb/usb-device.txt
+		 At the time of writing, the only OF supported devices
+		 (more may be added later) are:
+
+		  "usb1286,204e" (Marvell 8997)
+
+Optional properties:
+
+  - interrupt-parent: phandle of the parent interrupt controller
+  - interrupt-names: (see below)
+  - interrupts : The interrupt specified by the name "wakeup" is the interrupt
+		 that shall be used for out-of-band wake-on-bt. Driver will
+		 request this interrupt for wakeup. During system suspend, the
+		 irq will be enabled so that the bluetooth chip can wakeup host
+		 platform out of band. During system resume, the irq will be
+		 disabled to make sure unnecessary interrupt is not received.
+
+Example:
+
+Following example uses irq pin number 3 of gpio0 for out of band wake-on-bt:
+
+&usb_host1_ehci {
+    status = "okay";
+    #address-cells = <1>;
+    #size-cells = <0>;
+
+    mvl_bt1: bt@1 {
+	compatible = "usb1286,204e";
+	reg = <1>;
+	interrupt-parent = <&gpio0>;
+	interrupt-name = "wakeup";
+	interrupts = <3 IRQ_TYPE_LEVEL_LOW>;
+    };
+};

drivers/bluetooth/btusb.c

@@ -24,6 +24,8 @@
 #include <linux/module.h>
 #include <linux/usb.h>
 #include <linux/firmware.h>
+#include <linux/of_device.h>
+#include <linux/of_irq.h>
 #include <asm/unaligned.h>
 
 #include <net/bluetooth/bluetooth.h>
@@ -373,6 +375,7 @@ static const struct usb_device_id blacklist_table[] = {
 #define BTUSB_BOOTING		9
 #define BTUSB_RESET_RESUME	10
 #define BTUSB_DIAG_RUNNING	11
+#define BTUSB_OOB_WAKE_ENABLED	12
 
 struct btusb_data {
 	struct hci_dev       *hdev;
@@ -420,6 +423,8 @@ struct btusb_data {
 	int (*recv_bulk)(struct btusb_data *data, void *buffer, int count);
 
 	int (*setup_on_usb)(struct hci_dev *hdev);
+
+	int oob_wake_irq;   /* irq for out-of-band wake-on-bt */
 };
 
 static inline void btusb_free_frags(struct btusb_data *data)
@@ -2732,6 +2737,66 @@ static int btusb_bcm_set_diag(struct hci_dev *hdev, bool enable)
 }
 #endif
 
+#ifdef CONFIG_PM
+static irqreturn_t btusb_oob_wake_handler(int irq, void *priv)
+{
+	struct btusb_data *data = priv;
+
+	pm_wakeup_event(&data->udev->dev, 0);
+
+	/* Disable only if not already disabled (keep it balanced) */
+	if (test_and_clear_bit(BTUSB_OOB_WAKE_ENABLED, &data->flags)) {
+		disable_irq_nosync(irq);
+		disable_irq_wake(irq);
+	}
+	return IRQ_HANDLED;
+}
+
+static const struct of_device_id btusb_match_table[] = {
+	{ .compatible = "usb1286,204e" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, btusb_match_table);
+
+/* Use an oob wakeup pin? */
+static int btusb_config_oob_wake(struct hci_dev *hdev)
+{
+	struct btusb_data *data = hci_get_drvdata(hdev);
+	struct device *dev = &data->udev->dev;
+	int irq, ret;
+
+	clear_bit(BTUSB_OOB_WAKE_ENABLED, &data->flags);
+
+	if (!of_match_device(btusb_match_table, dev))
+		return 0;
+
+	/* Move on if no IRQ specified */
+	irq = of_irq_get_byname(dev->of_node, "wakeup");
+	if (irq <= 0) {
+		bt_dev_dbg(hdev, "%s: no OOB Wakeup IRQ in DT", __func__);
+		return 0;
+	}
+
+	ret = devm_request_irq(&hdev->dev, irq, btusb_oob_wake_handler,
+			       0, "OOB Wake-on-BT", data);
+	if (ret) {
+		bt_dev_err(hdev, "%s: IRQ request failed", __func__);
+		return ret;
+	}
+
+	ret = device_init_wakeup(dev, true);
+	if (ret) {
+		bt_dev_err(hdev, "%s: failed to init_wakeup", __func__);
+		return ret;
+	}
+
+	data->oob_wake_irq = irq;
+	disable_irq(irq);
+	bt_dev_info(hdev, "OOB Wake-on-BT configured at IRQ %u", irq);
+	return 0;
+}
+#endif
+
 static int btusb_probe(struct usb_interface *intf,
 		       const struct usb_device_id *id)
 {
@@ -2853,6 +2918,11 @@ static int btusb_probe(struct usb_interface *intf,
 	hdev->send   = btusb_send_frame;
 	hdev->notify = btusb_notify;
 
+#ifdef CONFIG_PM
+	err = btusb_config_oob_wake(hdev);
+	if (err)
+		goto out_free_dev;
+#endif
 	if (id->driver_info & BTUSB_CW6622)
 		set_bit(HCI_QUIRK_BROKEN_STORED_LINK_KEY, &hdev->quirks);
 
@@ -3065,6 +3135,9 @@ static void btusb_disconnect(struct usb_interface *intf)
 			usb_driver_release_interface(&btusb_driver, data->isoc);
 	}
 
+	if (data->oob_wake_irq)
+		device_init_wakeup(&data->udev->dev, false);
+
 	hci_free_dev(hdev);
 }
 
@@ -3093,6 +3166,12 @@ static int btusb_suspend(struct usb_interface *intf, pm_message_t message)
 	btusb_stop_traffic(data);
 	usb_kill_anchored_urbs(&data->tx_anchor);
 
+	if (data->oob_wake_irq && device_may_wakeup(&data->udev->dev)) {
+		set_bit(BTUSB_OOB_WAKE_ENABLED, &data->flags);
+		enable_irq_wake(data->oob_wake_irq);
+		enable_irq(data->oob_wake_irq);
+	}
+
 	/* Optionally request a device reset on resume, but only when
 	 * wakeups are disabled. If wakeups are enabled we assume the
 	 * device will stay powered up throughout suspend.
@@ -3130,6 +3209,12 @@ static int btusb_resume(struct usb_interface *intf)
 	if (--data->suspend_count)
 		return 0;
 
+	/* Disable only if not already disabled (keep it balanced) */
+	if (test_and_clear_bit(BTUSB_OOB_WAKE_ENABLED, &data->flags)) {
+		disable_irq(data->oob_wake_irq);
+		disable_irq_wake(data->oob_wake_irq);
+	}
+
 	if (!test_bit(HCI_RUNNING, &hdev->flags))
 		goto done;