[PATCH] Bluetooth: Add HCI_QUIRK_NO_SCAN_WHILE_CONNECTED for combo chips

[StefanCondorache <condorachest@gmail.com>]

Realtek combo chips share a single antenna between Wi-Fi and Bluetooth.
Background LE passive scanning while an active connection exists causes
antenna multiplexing conflicts via Packet Traffic Arbitration (PTA),
resulting in audio stuttering and Wi-Fi packet loss.

Add HCI_QUIRK_NO_SCAN_WHILE_CONNECTED to suppress passive scanning in
hci_update_passive_scan_sync() when active connections are present.
Set this quirk for all Realtek devices in btrtl_set_quirks().

Also add device ID 0x0bda:0xc829 to the btusb Realtek device table.

Signed-off-by: StefanCondorache <condorachest@gmail.com>
---
 drivers/bluetooth/btrtl.c   |  6 ++++++
 drivers/bluetooth/btusb.c   |  2 ++
 include/net/bluetooth/hci.h | 11 +++++++++++
 net/bluetooth/hci_sync.c    |  7 +++++++
 4 files changed, 26 insertions(+)

diff --git a/drivers/bluetooth/btrtl.c b/drivers/bluetooth/btrtl.c
index 62f9d4df3a4f..00dfba656970 100644
--- a/drivers/bluetooth/btrtl.c
+++ b/drivers/bluetooth/btrtl.c
@@ -1299,6 +1299,12 @@ EXPORT_SYMBOL_GPL(btrtl_download_firmware);
 
 void btrtl_set_quirks(struct hci_dev *hdev, struct btrtl_device_info *btrtl_dev)
 {
+	/* Realtek combo chips share the antenna between Wi-Fi and
+	 * Bluetooth. Suppress passive scanning while connected to
+	 * prevent coexistence issues.
+	 */
+	hci_set_quirk(hdev, HCI_QUIRK_NO_SCAN_WHILE_CONNECTED);
+
 	/* Enable controller to do both LE scan and BR/EDR inquiry
 	 * simultaneously.
 	 */
diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
index 5f57953393be..87972f5fc567 100644
--- a/drivers/bluetooth/btusb.c
+++ b/drivers/bluetooth/btusb.c
@@ -516,6 +516,8 @@ static const struct usb_device_id quirks_table[] = {
 	/* Realtek 8822CU Bluetooth devices */
 	{ USB_DEVICE(0x13d3, 0x3549), .driver_info = BTUSB_REALTEK |
 						     BTUSB_WIDEBAND_SPEECH },
+	{ USB_DEVICE(0x0bda, 0xc829), .driver_info = BTUSB_REALTEK |
+							 BTUSB_WIDEBAND_SPEECH },
 
 	/* Realtek 8851BE Bluetooth devices */
 	{ USB_DEVICE(0x0bda, 0xb850), .driver_info = BTUSB_REALTEK },
diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
index 572b1c620c5d..8466dc52aeca 100644
--- a/include/net/bluetooth/hci.h
+++ b/include/net/bluetooth/hci.h
@@ -378,6 +378,17 @@ enum {
 	 */
 	HCI_QUIRK_BROKEN_READ_PAGE_SCAN_TYPE,
 
+	/* When this quirk is set, the controller suppresses passive LE
+	 * background scanning while an active connection exists.
+	 * This is required for combo chips with shared Wi-Fi/Bluetooth
+	 * antennas to prevent coexistence issues causing audio drops
+	 * and Wi-Fi packet loss.
+	 *
+	 * This quirk can be set before hci_register_dev is called or
+	 * during the hdev->setup vendor callback.
+	 */
+	HCI_QUIRK_NO_SCAN_WHILE_CONNECTED,
+
 	__HCI_NUM_QUIRKS,
 };
 
diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index fd3aacdea512..5e30e725efa2 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -3194,6 +3194,13 @@ int hci_update_passive_scan_sync(struct hci_dev *hdev)
 	if (hdev->discovery.state != DISCOVERY_STOPPED)
 		return 0;
 
+	/* If the controller requires no scanning while connected,
+	 * suppress passive scanning when an active connection exists.
+	 */
+	if (hci_test_quirk(hdev, HCI_QUIRK_NO_SCAN_WHILE_CONNECTED) &&
+	    !list_empty(&hdev->conn_hash.list))
+		return 0;
+
 	/* Reset RSSI and UUID filters when starting background scanning
 	 * since these filters are meant for service discovery only.
 	 *
-- 
2.53.0