Hello Marcel,
On Fri, Jul 23, 2021 at 02:19:09PM +0200, Marcel Holtmann wrote:
> Hi Pauli,
>
> > 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@xxxxxx>
> > Fixes: e848dbd364ac ("Bluetooth: btusb: Add support USB ALT 3 for WBS")
>
> before I will apply this, I need Tested-by or Ack-by people that confirm that this fixes their issues now.
>
Is v3 ok/enough? It has one Tested-by.
It would probably be good to send v4 anyway with CC stable@xxxxxxxxxx ..
Thanks,
-- Pasi
>
> > ---
> >
> > Changes in v2:
> > - Explain magic number 72 in a comment; didn't add the table for them,
> > because it's not used elsewhere and we need just one number from it.
> > - Add flag for ALT3 support, restoring the behavior
> > for non-Realtek devices the same as before e848dbd364ac, due to
> > the problems reported on an Intel adapter. Don't have the device
> > myself.
> >
> > 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..5cec719f6cba 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_ALT3_OK_FOR_WBS 15
>
> Rename this to BTUSB_USE_ALT3_FOR_WBS.
>
> >
> > 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_ALT3_OK_FOR_WBS, &data->flags) &&
> > + hdev->sco_mtu >= 72 &&
> > + btusb_find_altsetting(data, 3))
>
> This is whitespace damaged.
>
> > 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_ALT3_OK_FOR_WBS, &data->flags);
> > }
>
> Regards
>
> Marcel
>
