From: Pauli Virtanen pav@iki.fi
commit 55981d3541812234e687062926ff199c83f79a39 upstream.
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 pav@iki.fi Fixes: e848dbd364ac ("Bluetooth: btusb: Add support USB ALT 3 for WBS") Tested-by: Michał Kępień kernel@kempniu.pl Tested-by: Jonathan Lampérth jon@h4n.dev Signed-off-by: Luiz Augusto von Dentz luiz.von.dentz@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/bluetooth/btusb.c | 22 ++++++++++++++-------- 1 file changed, 14 insertions(+), 8 deletions(-)
--- a/drivers/bluetooth/btusb.c +++ b/drivers/bluetooth/btusb.c @@ -486,6 +486,7 @@ static const struct dmi_system_id btusb_ #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; @@ -1718,16 +1719,20 @@ static void btusb_work(struct work_struc /* 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 (btusb_find_altsetting(data, 3) && + hdev->sco_mtu >= 72 && + test_bit(BTUSB_USE_ALT3_FOR_WBS, &data->flags)) new_alts = 3; + else + new_alts = 1; }
if (btusb_switch_alt_setting(hdev, new_alts) < 0) @@ -4170,6 +4175,7 @@ static int btusb_probe(struct usb_interf * (DEVICE_REMOTE_WAKEUP) */ set_bit(BTUSB_WAKEUP_DISABLE, &data->flags); + set_bit(BTUSB_USE_ALT3_FOR_WBS, &data->flags); }
if (!reset)