Kernel Kernel bug caused by (cpufreq: mediatek: Refine mtk_cpufreq_voltage_tracking()) on Banana Pi R64 (MT7622)

Fri Dec 2 03:00:41 PST 2022

Il 02/12/22 11:41, Thorsten Leemhuis ha scritto:
> On 02.12.22 11:02, AngeloGioacchino Del Regno wrote:
>> Il 02/12/22 10:43, Allen-KH Cheng (程冠勳) ha scritto:
>>>
>>> Jia-wei is working on this issue.
>>> We will update progress ASAP.
>>>
>>
>> I think I've found something: the MT7622/7623 voltage constraints
>> set in mediatek-cpufreq's platform data seem to be wrong.
> 
> Thx for looking into this.
>> I've sent a commit to fix those [1]
> 
> Quick question: is that relative to apply at this point of the 6.1 devel
> cycle? Or would it be better to revert the culprit (already introduced
> in 5.19) for now and reapply it together with that fix for 6.2 (and then
> backport to 6.1 stable later)?
> 
>> and that should solve the issue
>> that was seen on MT7622, but the code in the voltage tracking algorithm
>> is unsafe: this crash should be happening because we may be calling
>> regulator_set_voltage() with max_uV < min_uV --- and this is not legal.
> 
> [...]
> 
>> [1]:
>> https://lore.kernel.org/lkml/20221202095227.167492-1-angelogioacchino.delregno@collabora.com/
> 
> Side note, that patch afaics should have:
> 
> Reported-by: Nick <vincent at systemli.org>
> Link:
> https://lore.kernel.org/r/930778a1-5e8b-6df6-3276-42dcdadaf682@systemli.org/
> 

I'm sorry, forgot about those. I'll wait for feedback on that patch first.

If Viresh can add those while applying the patch, that's fine for me - otherwise
I can send a v2 adding the two suggested missing tags.

Thanks all!
Angelo

> To explain: Linus[1] and others considered proper link tags important in
> cases like this, as they allow anyone to look into the backstory of a
> commit weeks or years later. That's nothing new, the documentation[2]
> for some time says to place tags in cases like this. I care personally
> (and made it a bit more explicit in the docs a while ago), because these
> tags make my regression tracking efforts a whole lot easier, as they
> allow my tracking bot 'regzbot' to automatically connect reports with
> patches posted or committed to fix tracked regressions.
> 
> Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
> 
> [1] for details, see:
> https://lore.kernel.org/all/CAHk-=wjMmSZzMJ3Xnskdg4+GGz=5p5p+GSYyFBTh0f-DgvdBWg@mail.gmail.com/
> https://lore.kernel.org/all/CAHk-=wgs38ZrfPvy=nOwVkVzjpM3VFU1zobP37Fwd_h9iAD5JQ@mail.gmail.com/
> https://lore.kernel.org/all/CAHk-=wjxzafG-=J8oT30s7upn4RhBs6TX-uVFZ5rME+L5_DoJA@mail.gmail.com/
> 
> [2] see Documentation/process/submitting-patches.rst
> (http://docs.kernel.org/process/submitting-patches.html) and
> Documentation/process/5.Posting.rst
> (https://docs.kernel.org/process/5.Posting.html)
> 
> 
> 
>>> Thanks,
>>> Allen
>>>
>>> On Fri, 2022-12-02 at 10:19 +0100, AngeloGioacchino Del Regno wrote:
>>>> Il 02/12/22 09:57, AngeloGioacchino Del Regno ha scritto:
>>>>> Il 02/12/22 06:27, Viresh Kumar ha scritto:
>>>>>> On 01-12-22, 16:39, Thorsten Leemhuis wrote:
>>>>>>> Thx for clarifying. And I noticed I made a mistake: I should
>>>>>>> have
>>>>>>> directed my earlier question wrt to any progress here more into
>>>>>>> the
>>>>>>> direction of Jia-Wei Chang (who authored 6a17b3876b) and Viresh
>>>>>>> Kumar
>>>>>>> (who committed it).
>>>>>>
>>>>>> I was waiting for the platform maintainers to come up with a fix.
>>>>>> I
>>>>>> have sent a patch now to revert this, in-reply-to this thread.
>>>>>>
>>>>>> Please confirm this is working fine. Thanks.
>>>>>>
>>>>>
>>>>> Can you guys try this patch that I've sent a while ago?
>>>>>
>>>>>
>>> https://lore.kernel.org/lkml/20220909093724.40078-1-angelogioacchino.delregno@collabora.com/T/#u
>>>>>
>>>>> There were comments on it, but if that solves your issue I can push
>>>>> a v2
>>>>> to solve what was reported.
>>>>>
>>>>> Regards,
>>>>> Angelo
>>>>
>>>> Wait, sorry, I've re-read the stacktrace and that won't help at all.
>>>> MediaTek, can you please look at this issue?
>>>>
>>>> Reverting the proposed commit will make MT8183 unstable.
>>>>
>>>>
> 
> #regzbot monitor:
> https://lore.kernel.org/r/930778a1-5e8b-6df6-3276-42dcdadaf682@systemli.org/

-- 
AngeloGioacchino Del Regno
Software Engineer

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