[ Upstream commit 5d44ab9e204200a78ad55cdf185aa2bb109b5950 ]
On most devices using the btqcomsmd driver (e.g. the DragonBoard 410c
and other devices based on the Qualcomm MSM8916/MSM8909/... SoCs)
the Bluetooth firmware seems to become unresponsive for a while after
setting the BD address. On recent kernel versions (at least 5.17+)
this often causes timeouts for subsequent commands, e.g. the HCI reset
sent by the Bluetooth core during initialization:
Bluetooth: hci0: Opcode 0x c03 failed: -110
Unfortunately this behavior does not seem to be documented anywhere.
Experimentation suggests that the minimum necessary delay to avoid
the problem is ~150us. However, to be sure add a sleep for > 1ms
in case it is a bit longer on other firmware versions.
Older kernel versions are likely also affected, although perhaps with
slightly different errors or less probability. Side effects can easily
hide the issue in most cases, e.g. unrelated incoming interrupts that
cause the necessary delay.
Fixes: 1511cc750c ("Bluetooth: Introduce Qualcomm WCNSS SMD based HCI driver")
Signed-off-by: Stephan Gerhold <stephan.gerhold@kernkonzept.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
65ceb17074