Bluetooth: btusb: Ignore zero length of USB packets on ALT 6 for specific chip

For USB ALT 6 settings some Realtek chips need to transmit mSBC data
continuously without the zero length of USB packets.
In this commit, create BTUSB_ALT6_CONTINUOUS_TX to manage the behavior.
Therefore, create REALTEK_ALT6_CONTINUOUS_TX_CHIP to manage the specific
chip model for the behavior.
Signed-off-by: Max Chou <max.chou@realtek.com>
Signed-off-by: Hilda Wu <hildawu@realtek.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

drivers/bluetooth/btrtl.c

@@ -781,6 +781,13 @@ void btrtl_set_quirks(struct hci_dev *hdev, struct btrtl_device_info *btrtl_dev)
 	case CHIP_ID_8852C:
 		set_bit(HCI_QUIRK_VALID_LE_STATES, &hdev->quirks);
 		set_bit(HCI_QUIRK_WIDEBAND_SPEECH_SUPPORTED, &hdev->quirks);
+
+		/* RTL8852C needs to transmit mSBC data continuously without
+		 * the zero length of USB packets for the ALT 6 supported chips
+		 */
+		if (btrtl_dev->project_id == CHIP_ID_8852C)
+			btrealtek_set_flag(hdev, REALTEK_ALT6_CONTINUOUS_TX_CHIP);
+
 		hci_set_aosp_capable(hdev);
 		break;
 	default:

drivers/bluetooth/btusb.c

@@ -632,6 +632,7 @@ static const struct dmi_system_id btusb_needs_reset_resume_table[] = {
 #define BTUSB_TX_WAIT_VND_EVT	13
 #define BTUSB_WAKEUP_AUTOSUSPEND	14
 #define BTUSB_USE_ALT3_FOR_WBS	15
+#define BTUSB_ALT6_CONTINUOUS_TX	16
 
 struct btusb_data {
 	struct hci_dev       *hdev;
@@ -1322,11 +1323,17 @@ static void btusb_isoc_complete(struct urb *urb)
 static inline void __fill_isoc_descriptor_msbc(struct urb *urb, int len,
 					       int mtu, struct btusb_data *data)
 {
-	int i, offset = 0;
+	int i = 0, offset = 0;
 	unsigned int interval;
 
 	BT_DBG("len %d mtu %d", len, mtu);
 
+	/* For mSBC ALT 6 settings some chips need to transmit the data
+	 * continuously without the zero length of USB packets.
+	 */
+	if (test_bit(BTUSB_ALT6_CONTINUOUS_TX, &data->flags))
+		goto ignore_usb_alt6_packet_flow;
+
 	/* For mSBC ALT 6 setting the host will send the packet at continuous
 	 * flow. As per core spec 5, vol 4, part B, table 2.1. For ALT setting
 	 * 6 the HCI PACKET INTERVAL should be 7.5ms for every usb packets.
@@ -1346,6 +1353,7 @@ static inline void __fill_isoc_descriptor_msbc(struct urb *urb, int len,
 		urb->iso_frame_desc[i].length = offset;
 	}
 
+ignore_usb_alt6_packet_flow:
 	if (len && i < BTUSB_MAX_ISOC_FRAMES) {
 		urb->iso_frame_desc[i].offset = offset;
 		urb->iso_frame_desc[i].length = len;
@@ -2368,6 +2376,19 @@ static int btusb_send_frame_intel(struct hci_dev *hdev, struct sk_buff *skb)
 	return -EILSEQ;
 }
 
+static int btusb_setup_realtek(struct hci_dev *hdev)
+{
+	struct btusb_data *data = hci_get_drvdata(hdev);
+	int ret;
+
+	ret = btrtl_setup_realtek(hdev);
+
+	if (btrealtek_test_flag(data->hdev, REALTEK_ALT6_CONTINUOUS_TX_CHIP))
+		set_bit(BTUSB_ALT6_CONTINUOUS_TX, &data->flags);
+
+	return ret;
+}
+
 /* UHW CR mapping */
 #define MTK_BT_MISC		0x70002510
 #define MTK_BT_SUBSYS_RST	0x70002610
@@ -3969,7 +3990,7 @@ static int btusb_probe(struct usb_interface *intf,
 
 	if (IS_ENABLED(CONFIG_BT_HCIBTUSB_RTL) &&
 	    (id->driver_info & BTUSB_REALTEK)) {
-		hdev->setup = btrtl_setup_realtek;
+		hdev->setup = btusb_setup_realtek;
 		hdev->shutdown = btrtl_shutdown_realtek;
 		hdev->cmd_timeout = btusb_rtl_cmd_timeout;