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From:   Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Date:   Tue, 1 Mar 2022 10:34:48 -0800
Message-ID: <CABBYNZLnMwod+pgomEfvu83AJ=jM+uqwK9-Eqj6fA9_wXg6HBA@mail.gmail.com>
Subject: Re: bug kernel 5.17, qualcom and intel adapters, unable to reliably
 connect to bluetooth devices
To:     Chris Clayton <chris2553@googlemail.com>
Cc:     Chris Murphy <lists@colorremedies.com>,
        Bluetooth <linux-bluetooth@vger.kernel.org>,
        regressions@lists.linux.dev
Content-Type: text/plain; charset="UTF-8"
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Hi Chris,

On Tue, Mar 1, 2022 at 1:26 AM Chris Clayton <chris2553@googlemail.com> wrote:
>
> Hi Luiz,
>
> I guess you are hoping for PEBKAC :-)
>
> On 28/02/2022 21:20, Luiz Augusto von Dentz wrote:
> > Hi Chris,
> >
> > On Mon, Feb 28, 2022 at 1:02 PM Chris Clayton <chris2553@googlemail.com> wrote:
> >>
> >> Hi Luiz,
> >>
> >> On 28/02/2022 19:34, Luiz Augusto von Dentz wrote:
> >>> Hi Chris,
> >>>
> >>> On Sat, Feb 26, 2022 at 12:04 AM Chris Clayton <chris2553@googlemail.com> wrote:
> >>>>
> >>>> Hi,
> >>>>
> >>>> On 24/02/2022 15:16, Luiz Augusto von Dentz wrote:
> >>>>>> I'll try another bisection today, but limit its range to changes made in the net/bluetooth directory.
> >>>>
> >>>> That  bisection has proved very difficult because the bluetooth "service" in kernels at some steps of the bisection were
> >>>> completely borked to the extent that blueman's device-manager application wouldn't start and emitted the messages:
> >>>>
> >>>> blueman-manager 12.00.37 ERROR    Manager:137 on_dbus_name_appeared: Default adapter not found, trying first available.
> >>>> blueman-manager 12.00.37 ERROR    Manager:141 on_dbus_name_appeared: No adapter(s) found, exiting
> >>>>
> >>>> Obviously, I don't know whether the problem I am trying to pinpoint is hiding behind this more fundamental problem with
> >>>> the bluetooth "service", so being unable to say whether that kernel was good or bad, I had to skip. There seems to be a
> >>>> batch of commits that mean that, whilst the kernel builds okay, hunting down a bluetooth-related problem is not
> >>>> possible. Eventually and I cursed and gave up. Whatever was causing this breakage has obviously been fixed.
> >>>>
> >>>>> Please record the HCI with btmon, it must be producing something since
> >>>>> it records even the mgmt commands.
> >>>>>
> >>>>
> >>>> Refreshed by a good night's sleep, I started another bisection (between 5.16 and 5.17-rc1) yesterday morning but this
> >>>> time did not limit it to net/bluetooth.  That was going okay until I ran into what I assume is the same batch of borked
> >>>> kernels. I've been more persistent this time but have just had a run of 16 steps in which the bluetooth support in the
> >>>> kernel is broken so badly that testing bluetooth is not possible. I will push on today, but I've suspended that activity
> >>>> to get the hci trace that Luiz has asked for.
> >>>>
> >>>> Using information from the bisect, I built a kernel that had tested as bad (but not borked). The commit is
> >>>> f2b551fad8d8f2ac5e1f810ad595298381e0b0c5. As I've mentioned before, the problem with devices not connecting is
> >>>> intermittent - for a given kernel, sometimes a connection works and other times it doesn't. On the first boot of this
> >>>> kernel, my bluetooth devices could connect, Attached are 4 files related to this - the output from btmon, and the
> >>>> related portions of daemon.log, kern.log and sys.log from /var/log/. Each of the these files is suffixed with ".good".
> >>>>
> >>>> I then powered down the laptop and booted into the same kernel. This time the bluetooth devices could not connect. Four
> >>>> more files are attached for this boot and are suffixed with ".bad". I said in an earlier email that when connection
> >>>> fails, there is no output from btmon, so that log is empty. That's still the case, but I guess that fact itself is a
> >>>> clue to what the problem might be. What I can add, however, is that if, in that same bad kernel, I unload and then
> >>>> reload the btusb module, connections start to work. Maybe that too is a clue. The same unload/load process revives
> >>>> bluetooth on a kernel built after a pull of Linus' latest and greatest this morning.
> >>>>
> >>>> Since I now have a workround, I'm going stop the current bisection that I was doing.  I've done another couple of steps
> >>>> this morning and both produced kernels on which I could not test bluetooth and had to tell git bisect to skip. If
> >>>> however, I can provide any other diagnostics, please let me know.
> >>>>
> >>>> Chris
> >>>
> >>> Can you try with the following patch:
> >>>
> >>> https://patchwork.kernel.org/project/bluetooth/patch/20220228173918.524733-1-brian.gix@intel.com/
> >>>
> >>>
> >> Sorry, that patch has made no difference. After the first boot my headphones connected okay, but after a power-down and
> >> reboot they would not connect without an unload and reload of the btusb module.
> >
> > Can you tell us exactly what steps you are using? Are you applying on
> > top of what, rc6?
> >
>
> Until I got your patch yesterday, I was using a clone of
> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git which I update frequently and have been doing so for as
> long as I can remember. Just in case there was a hidden flaw in that tree, I took a new clone yesterday, (so yes, the
> patch was tested on top of rc6) copied over the .config file and applied the patch. Then I built and installed the
> kernel, updated grub, powered off the laptop and booted into the new kernel. Once the laptop had booted and logged in to
> my LXQt desktop, I powered on my headphones and a connection was establisehed almost straight away. I powered the
> headphones off and the disconnection worked fine.
>
> Knowing that the problem crops up intermittently, I then rebooted the laptop. When the boot was complete, I then powered
> on my bluetooth headphones an waited for them to connect to the laptop. After about 20 seconds, a connection had not
> been established. I powered off the headphones, used modprobe to unload and then reload the btusb module. When I powered
> on the headphones, a connectiin was established within 2 or 3 seconds.
>
> I've booted this laptop countless times over the last few days. Doing the bisect, I didn't mark a commit as good until I
> had done five boots and been able to connect my headphones on each boot. What I can say from that work is that two
> consecutive boots into a working kernel are very rare. I can't remeber an occasion when it took more than two boots to
> establish that a kernel was bad.

Do commands such as bluetoothctl power on or scan on works? Try
running bluetoothd -dn from a shell (disable bluetooth.service), also
are there any settings changed in main.conf?


-- 
Luiz Augusto von Dentz