[PATCH v4 1/2] Bluetooth: btusb: mediatek: Fix leaked runtime PM reference in reset

[Jiajia Liu]

MT7925 on HP Pro Mini 260 sometimes timed out during reloading driver
and reset usb device. btusb_suspend is not called again after closing
bluetooth interface.

 usbcore: registered new interface driver btusb
 Bluetooth: hci0: HW/SW Version: 0x00000000, Build Time: 20260605184935
 Bluetooth: hci0: Execution of wmt command timed out
 Bluetooth: hci0: Failed to send wmt patch dwnld (-110)
 Bluetooth: hci0: Failed to set up firmware (-110)
 usb 3-10: reset high-speed USB device number 4 using xhci_hcd
 Bluetooth: hci0: HW/SW Version: 0x00000000, Build Time: 20260605184935
 Bluetooth: hci0: Device setup in 1856545 usecs
 Bluetooth: hci0: AOSP extensions version v1.00
 Bluetooth: hci0: AOSP quality report is supported
 Bluetooth: MGMT ver 1.23

btusb_mtk_reset calls usb_autopm_get_interface to resume the device
before driving the hardware reset, but never calls the matching
usb_autopm_put_interface. Every hardware reset therefore leaks a PM
usage reference of the interface, preventing the device from being
runtime suspended again until it is unbound.

Add the BTUSB_RESET flag. It is set before usb_queue_reset_device
and is cleared in btusb_disconnect, which drops the reference as well.
If the flag is already set when a new reset is requested, drop one
reference.

Also clear BTMTK_HW_RESET_ACTIVE if usb_autopm_get_interface fails,
otherwise no further reset could ever be attempted.

Fixes: 25b6d7593a3a ("Bluetooth: btmtk: introduce btmtk reset work")
Assisted-by: Claude:qwen3.8-max
Signed-off-by: Jiajia Liu <liujiajia@xxxxxxxxxx>
---

Changes in v4:
- do not return if BTUSB_RESET is set in case the first reset failed.
  move test_and_set_bit right before usb_queue_reset_device (sashiko)

Changes in v3:
- rename BTUSB_USB_RESET_ACTIVE to BTUSB_RESET (Luiz)

- test_and_clear_bit BTUSB_RESET in btusb_disconnect (Luiz)

- handle multiple reset requests int btusb_mtk_reset (sashiko)
  set BTUSB_RESET if no reset_gpio after usb_autopm_get_interface.
  If the flag is already set, add log and drop newly acquired reference
  and return.

- clear BTMTK_HW_RESET_ACTIVE if usb_autopm_get_interface fails and add
  error log. (sashiko)

---
 drivers/bluetooth/btusb.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
index 184e95c1625e5..c95f72484fc0f 100644
--- a/drivers/bluetooth/btusb.c
+++ b/drivers/bluetooth/btusb.c
@@ -957,6 +957,7 @@ struct qca_dump_info {
 #define BTUSB_USE_ALT3_FOR_WBS	15
 #define BTUSB_ALT6_CONTINUOUS_TX	16
 #define BTUSB_HW_SSR_ACTIVE	17
+#define BTUSB_RESET		18
 
 struct btusb_data {
 	struct hci_dev       *hdev;
@@ -2891,8 +2892,11 @@ static int btusb_mtk_reset(struct hci_dev *hdev, void *rst_data)
 	}
 
 	err = usb_autopm_get_interface(data->intf);
-	if (err < 0)
+	if (err < 0) {
+		bt_dev_err(hdev, "Failed usb_autopm_get_interface: %d", err);
+		clear_bit(BTMTK_HW_RESET_ACTIVE, &btmtk_data->flags);
 		return err;
+	}
 
 	/* Release MediaTek ISO data interface */
 	btusb_mtk_release_iso_intf(hdev);
@@ -2915,6 +2919,11 @@ static int btusb_mtk_reset(struct hci_dev *hdev, void *rst_data)
 
 	err = btmtk_usb_subsys_reset(hdev, btmtk_data->dev_id);
 
+	if (test_and_set_bit(BTUSB_RESET, &data->flags)) {
+		bt_dev_err(hdev, "last usb reset failed? Resetting again");
+		usb_autopm_put_interface_no_suspend(data->intf);
+	}
+
 	usb_queue_reset_device(data->intf);
 	clear_bit(BTMTK_HW_RESET_ACTIVE, &btmtk_data->flags);
 
@@ -4497,6 +4506,9 @@ static void btusb_disconnect(struct usb_interface *intf)
 	if (data->reset_gpio)
 		gpiod_put(data->reset_gpio);
 
+	if (test_and_clear_bit(BTUSB_RESET, &data->flags))
+		usb_autopm_put_interface_no_suspend(data->intf);
+
 	if (intf == data->intf) {
 		if (data->isoc)
 			usb_driver_release_interface(&btusb_driver, data->isoc);
-- 
2.53.0