[PATCH v2 3/3] Bluetooth: btsub: Ignore zero length of USB packets on ALT 6 for the specific chip model of Realtek devices

[<hildawu@realtek.com>]

From: Hilda Wu <hildawu@realtek.com>

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 workaround.
Therefore, create REALTEK_ALT6_CONTINUOUS_TX_CHIP to manage the specific
chip model for the workaround.

Signed-off-by: Max Chou <max.chou@realtek.com>
Signed-off-by: Hilda Wu <hildawu@realtek.com>
---
 drivers/bluetooth/btrtl.c |  7 +++++++
 drivers/bluetooth/btusb.c | 14 +++++++++++++-
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/drivers/bluetooth/btrtl.c b/drivers/bluetooth/btrtl.c
index 15223b3ed94d..6d74175cd25f 100644
--- a/drivers/bluetooth/btrtl.c
+++ b/drivers/bluetooth/btrtl.c
@@ -782,6 +782,13 @@ void btrtl_set_quirks(struct hci_dev *hdev, struct btrtl_device_info *btrtl_dev)
 		set_bit(HCI_QUIRK_VALID_LE_STATES, &hdev->quirks);
 		set_bit(HCI_QUIRK_WIDEBAND_SPEECH_SUPPORTED, &hdev->quirks);
 		btrealtek_set_flag(hdev, REALTEK_WBS_FILTER);
+
+		/* 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:
diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
index 8e595e03655a..50a21061350e 100644
--- a/drivers/bluetooth/btusb.c
+++ b/drivers/bluetooth/btusb.c
@@ -626,6 +626,7 @@ 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;
@@ -1284,11 +1285,18 @@ 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 Realtek chips need to transmit the data
+	 * continuously without the zero length of USB packets.
+	 */
+	if (test_bit(BTUSB_ALT6_CONTINUOUS_TX, &data->flags))
+		if (btrealtek_test_flag(data->hdev, REALTEK_ALT6_CONTINUOUS_TX_CHIP))
+			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.
@@ -1308,6 +1316,7 @@ 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;
@@ -3931,6 +3940,9 @@ static int btusb_probe(struct usb_interface *intf,
 		/* Realtek devices need to set remote wakeup on auto-suspend */
 		set_bit(BTUSB_WAKEUP_AUTOSUSPEND, &data->flags);
 		set_bit(BTUSB_USE_ALT3_FOR_WBS, &data->flags);
+
+		/* Some Realtek devices need to transmit mSBC data continuously */
+		set_bit(BTUSB_ALT6_CONTINUOUS_TX, &data->flags);
 	}
 
 	if (!reset)
-- 
2.17.1