BT / serial regression introduced during the recent 4.9-rc1 merge?

["Jérôme de Bretagne" <jerome.debretagne@gmail.com>]

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Hi Marcel, hi everyone,

I've compiled the latest bluetooth-next branch and I'm facing what looks
like a regression to me (still on a Lenovo ThinkPad 8 tablet): btattach
doesn't properly initialize the Broadcom BCM2E55 chipset anymore. 

I'm getting various timeout messages in dmesg:

[   13.188057] Bluetooth: hci0 command 0xfc45 tx timeout
[   16.093068] serial8250_interrupt: 4158 callbacks suppressed
[   16.093072] serial8250: too much work for irq39
[   16.094287] serial8250: too much work for irq39
...
[   16.103868] serial8250: too much work for irq39
[   21.100041] serial8250_interrupt: 4167 callbacks suppressed
[   21.100044] serial8250: too much work for irq39
...
[   21.222065] Bluetooth: hci0: BCM: failed to write clock (-110)
[   23.238528] Bluetooth: hci0 command 0x0c03 tx timeout
[   26.104253] serial8250_interrupt: 4165 callbacks suppressed
[   26.104257] serial8250: too much work for irq39

which I never had before and Bluetooth never actually starts.

Bluetooth doesn't init with a kernel built with the latest commit from
yesterday 526c86021e5102b8a4b5555b4196f7a19f44e2c4. 

I've gone back in time and it doesn't work either with a kernel built at 	
e6445f52d9c8b0e6557a45fa7d0e8e088d430a8c "Merge tag 'usb-4.9-rc1' of
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb".

It still worked at commit a2f195a73eba807006fb0cb882ecb552c06eea00
"bluetooth: bcm203x: don't print error when allocating urb fails" though,
which was the last previous commit modifying files in drivers/bluetooth in
the bluetooth-next branch.


I've attached the output of btmon when it used to work and one not working
(prefixed with .e6445f5) if that may be useful.


I'll continue my investigation in my spare time, trying to bissect to find
the culprit commit but there are hundreds of them so it will take me quite a
while. I'll focus on patches touching the serial 8250 driver to start with,
as there are only a few of them, but feel free to point me into a different
direction if you have another idea or suggestion. 

I wanted to share this early with the Bluetooth list as I didn't see the
issue mentioned until now. Feel free to forward this message to other lists
as it's likely coming from another kernel subsystem.   

Thanks,

Jérôme

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