From 3067de41319a25466c140cf55fb1364813828a18 Mon Sep 17 00:00:00 2001 From: Pauli Virtanen Date: Mon, 26 Jul 2021 21:02:06 +0300 Subject: [PATCH 2/4] Bluetooth: btusb: check conditions before enabling USB ALT 3 for WBS MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Some USB BT adapters don't satisfy the MTU requirement mentioned in commit e848dbd364ac ("Bluetooth: btusb: Add support USB ALT 3 for WBS") and have ALT 3 setting that produces no/garbled audio. Some adapters with larger MTU were also reported to have problems with ALT 3. Add a flag and check it and MTU before selecting ALT 3, falling back to ALT 1. Enable the flag for Realtek, restoring the previous behavior for non-Realtek devices. Tested with USB adapters (mtu<72, no/garbled sound with ALT3, ALT1 works) BCM20702A1 0b05:17cb, CSR8510A10 0a12:0001, and (mtu>=72, ALT3 works) RTL8761BU 0bda:8771, Intel AX200 8087:0029 (after disabling ALT6). Also got reports for (mtu>=72, ALT 3 reported to produce bad audio) Intel 8087:0a2b. Signed-off-by: Pauli Virtanen Fixes: e848dbd364ac ("Bluetooth: btusb: Add support USB ALT 3 for WBS") Tested-by: Michał Kępień Fixes: https://bugs.archlinux.org/task/71567 --- drivers/bluetooth/btusb.c | 22 ++++++++++++++-------- 1 file changed, 14 insertions(+), 8 deletions(-) diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c index 6d23308119d1..e8062d0b7d4d 100644 --- a/drivers/bluetooth/btusb.c +++ b/drivers/bluetooth/btusb.c @@ -516,6 +516,7 @@ static const struct dmi_system_id btusb_needs_reset_resume_table[] = { #define BTUSB_HW_RESET_ACTIVE 12 #define BTUSB_TX_WAIT_VND_EVT 13 #define BTUSB_WAKEUP_DISABLE 14 +#define BTUSB_USE_ALT3_FOR_WBS 15 struct btusb_data { struct hci_dev *hdev; @@ -1748,16 +1749,20 @@ static void btusb_work(struct work_struct *work) /* Bluetooth USB spec recommends alt 6 (63 bytes), but * many adapters do not support it. Alt 1 appears to * work for all adapters that do not have alt 6, and - * which work with WBS at all. + * which work with WBS at all. Some devices prefer + * alt 3 (HCI payload >= 60 Bytes let air packet + * data satisfy 60 bytes), requiring + * MTU >= 3 (packets) * 25 (size) - 3 (headers) = 72 + * see also Core spec 5, vol 4, B 2.1.1 & Table 2.1. */ - new_alts = btusb_find_altsetting(data, 6) ? 6 : 1; - /* Because mSBC frames do not need to be aligned to the - * SCO packet boundary. If support the Alt 3, use the - * Alt 3 for HCI payload >= 60 Bytes let air packet - * data satisfy 60 bytes. - */ - if (new_alts == 1 && btusb_find_altsetting(data, 3)) + if (btusb_find_altsetting(data, 6)) + new_alts = 6; + else if (test_bit(BTUSB_USE_ALT3_FOR_WBS, &data->flags) && + hdev->sco_mtu >= 72 && + btusb_find_altsetting(data, 3)) new_alts = 3; + else + new_alts = 1; } if (btusb_switch_alt_setting(hdev, new_alts) < 0) @@ -4733,6 +4738,7 @@ static int btusb_probe(struct usb_interface *intf, * (DEVICE_REMOTE_WAKEUP) */ set_bit(BTUSB_WAKEUP_DISABLE, &data->flags); + set_bit(BTUSB_USE_ALT3_FOR_WBS, &data->flags); } if (!reset) -- 2.32.0