linux-kernel - Re: [REGRESSION] Bluetooth is not working on Macs with BCM4377 chip starting from kernel 6.5

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Message-ID: <MA0P287MB0217A68FDF5E0DC22F19D3DCB8BBA@MA0P287MB0217.INDP287.PROD.OUTLOOK.COM>
Date:   Tue, 21 Nov 2023 11:42:28 +0000
From:   Aditya Garg <gargaditya08@...e.com>
To:     Hector Martin <marcan@...can.st>
CC:     Bagas Sanjaya <bagasdotme@...il.com>,
        Sven Peter <sven@...npeter.dev>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Luiz Augusto von Dentz <luiz.dentz@...il.com>,
        Orlando Chamberlain <orlandoch.dev@...il.com>,
        Kerem Karabay <kekrby@...il.com>,
        Aun-Ali Zaidi <admin@...eit.net>,
        Asahi Linux Mailing List <asahi@...ts.linux.dev>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Bluetooth <linux-bluetooth@...r.kernel.org>,
        "j@...nau.net" <j@...nau.net>
Subject: Re: [REGRESSION] Bluetooth is not working on Macs with BCM4377 chip
 starting from kernel 6.5



> On 20-Nov-2023, at 4:37 PM, Hector Martin <marcan@...can.st> wrote:
> 
> 
> 
>> On 2023/11/19 4:31, Aditya Garg wrote:
>> 
>> 
>>>> On 14-Nov-2023, at 3:14 PM, Hector Martin <marcan@...can.st> wrote:
>>> 
>>> On 14/11/2023 18.03, Aditya Garg wrote:
>>>> 
>>>> 
>>>>> On 14-Nov-2023, at 1:28 PM, Hector Martin <marcan@...can.st> wrote:
>>>>> 
>>>>> On 14/11/2023 15.59, Hector Martin wrote:
>>>>>> On 14/11/2023 15.23, Aditya Garg wrote:
>>>>>>> 
>>>>>>> 
>>>>>>>> On 14-Nov-2023, at 5:01 AM, Bagas Sanjaya <bagasdotme@...il.com> wrote:
>>>>>>>> 
>>>>>>>> On Mon, Nov 13, 2023 at 08:57:35PM +0000, Aditya Garg wrote:
>>>>>>>>> Starting from kernel 6.5, a regression in the kernel is causing Bluetooth to not work on T2 Macs with BCM4377 chip.
>>>>>>>>> 
>>>>>>>>> Journalctl of kernel 6.4.8 which has Bluetooth working is given here: https://pastebin.com/u9U3kbFJ
>>>>>>>>> 
>>>>>>>>> Journalctl of kernel 6.5.2, which has Bluetooth broken is given here: https://pastebin.com/aVHNFMRs
>>>>>>>>> 
>>>>>>>>> Also, the bug hasn’t been fixed even in 6.6.1, as reported by users.
>>>>>>>> 
>>>>>>>> Can you bisect this regression please?
>>>>>>> 
>>>>>>> Since I don't have access to this hardware, it's not possible for me to bisect this regression. Let's hope someone is able to do so though.
>>>>>> 
>>>>>> It's not a regression, it was always broken. I'm sending a patch.
>>>>>> 
>>>>>> - Hector
>>>>> 
>>>>> You are quite likely conflating two problems. The ubsan issue you quoted
>>>>> was always there and the patch I just sent fixes it, but it almost
>>>>> certainly always worked fine in practice without ubsan.
>>>>> 
>>>>> The Bluetooth problem you are referring to is likely *specific to
>>>>> Bluetooth LE devices* and the regression was introduced by 288c90224e
>>>>> and fixed by 41e9cdea9c, which is also in 6.5.11 and 6.6.1.
>>>>> 
>>>>> If Bluetooth is broken in *some other way* in 6.6.1 then we need a
>>>>> proper report or a bisect. Your logs don't show any issues other than
>>>>> the ubsan noise, which is not a regression.
>>>>> 
>>>>> - Hector
>>>>> 
>>>> 
>>>> UBSAN noise seems to be fixed, Bluetooth not working though
>>>> 
>>>> https://pastebin.com/HeVvMVk4
>>>> 
>>>> Ill try setting .broken_le_coded = true,
>>> 
>>> Now you have a probe timeout, which you didn't have before. That's a
>>> different problem.
>>> 
>>> Please try this commit and see if it helps:
>>> 
>>> https://github.com/AsahiLinux/linux/commit/8ec770b4f78fc14629705206e2db54d9d6439686
>>> 
>>> If it's this then it's still not a regression, it's probably just random
>>> chance since I think the old timeout value was borderline for the older
>>> chips.
>>> 
>>> - Hector
>>> 
>> 
>> 
>> Hi
>> 
>> I recently got a kernel tested with this patch as well as with .broken_le_coded = true,
>> Here are the logs: https://pastebin.com/BpfJuJKY
>> 
>> Also, without .broken_le_coded = true, the bluetooth doesn't work, as specified in my previous email.
> 
> So are you saying everything works now? If not, what doesn't work?
> "Bluetooth doesn't work" isn't useful information, especially in the
> absence of any useful error messages. You can't just dump dmesg logs at
> us, you have to *describe* what the problem is.
> 
My bad for not specifying that. The user reports that the Bluetooth device is not recognised at all.

Also, broken_le_coded = true did not "fix" it.

Talking about dmesg, well not getting any logs regarding this message indeed is a frustrating thing for me, and bisecting seems to be the only option in my mind rn.

> If broken_le_coded = true "fixed" it then "bluetooth doesn't work" was a
> terrible bug report. What that quirk does is make *connecting/pairing to
> Bluetooth LE devices* work. Non-BLE devices already worked, the
> controller worked, scanning worked, etc. All that is useful information
> if you want to get support for issues. We can't magically divine what's
> wrong if you just send us a dmesg and say "it's broken". We need
> detailed information about exactly what works and what doesn't (e.g. the
> controller not showing up at all is VERY different from it showing up
> but not finding your device). The only reason we guessed this here is
> that this was a known issue that affected other chips. If we ever run
> into a 4377-specific issue that only you can reproduce, "bluetooth
> doesn't work" and no error logs really isn't going to get it fixed.
> 
> - Hector