Re: [PATCH v2 1/2] Bluetooth: btbcm: raise ACL priority on Apple Broadcom controllers

[Myria Sarvay <myrialsarvay@gmail.com>]

On Thu, Nov 05, 2026 at 09:57:49AM +0100, Andre Eikmeyer wrote:
> On the MacBookPro15,1 (BCM4364B0 over UART) A2DP audio drops out as
> soon as WLAN runs on 2.4 GHz with traffic. The host keeps the eight ACL
> buffers of the controller filled, but the controller holds single ACL
> packets for 160-200 ms, so the sink runs dry.
> 
> Sending the Broadcom vendor command 0xfc57 (HCI_BRCM_SET_ACL_PRIORITY,
> handle and priority, as used by the Android Broadcom vendor library) with
> priority high for the audio link stops the dropouts. Setting it back to
> normal brings them back right away. The BCM4377 of the MacBookAir9,1
> accepts the command as well.
> 
> Raise the priority for every BR/EDR ACL link once its Connection Complete
> event arrives. This covers audio as well as HID links. hci_bcm does this
> on Apple machines only, hci_bcm4377 always, since it only runs on Apple
> machines. The PCIe driver receives events in hard interrupt context, so
> the command is queued from a work item.
Hi Andre,

Just wanted to point it out, if you hadn't seen it before, that Sasha
has in the past sent a different patch [1] to run these priority
commands. They seem to take a different approach to when to enable/run
them. Wasn't sure if one was better or worse though.

Thanks,
Myria

[1]: https://lore.kernel.org/asahi/20260525-brcm-prio-v3-1-6259e10233f8@chaosmail.tech/