Re: dmaengine: CPU stalls while loading bluetooth module

["Linux regression tracking (Thorsten Leemhuis)" <regressions@leemhuis.info>]

[CCing the regression list, as it should be in the loop for regressions:
https://docs.kernel.org/admin-guide/reporting-regressions.html]

On 05.03.24 08:13, bumyong.lee wrote:
>> we have encountered CPU stalls in mainline kernel while loading the
>> bluetooth module. We have custom board based on rockchip rv1109 soc and
>> there is bluetooth chipset of relatek 8821cs. CPU is stalls  while realtek
>> 8821cs module.
>>
>> Bug/Regression:
>> In current mainline, we found CPU is stalls when we load bluetooth module.
>> git bisect shows commit 22a9d9585812440211b0b34a6bc02ade62314be4
>> as a bad, which produce CPU stalls.
>>
>> git show 22a9d9585812440211b0b34a6bc02ade62314be4
>> commit 22a9d9585812440211b0b34a6bc02ade62314be4
>> Author: Bumyong Lee <bumyong.lee@samsung.com>
>> Date:   Tue Dec 19 14:50:26 2023 +0900
>>
>>      dmaengine: pl330: issue_pending waits until WFP state
>>
> [...]
>>
>> By reverting this commit, we have success in loading of bluetooth module.
> 
>> Output of CPU stalls:
> [...]
> 
> I discussed this issue. Could you refer to this[1]?
> I haven't received anymore reply from him after that.
> If you have any more opinion, please let me know.
> [1]: https://lore.kernel.org/lkml/000001da3869$ca643fa0$5f2cbee0$@samsung.com/T/

Hmmm. 6.8 final is due. Is that something we can live with? Or would it
be a good idea to revert above commit for now and reapply it when
something better emerged? I doubt that the answer is "yes, let's do
that", but I have to ask.

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
--
Everything you wanna know about Linux kernel regression tracking:
https://linux-regtracking.leemhuis.info/about/#tldr
If I did something stupid, please tell me, as explained on that page.

P.S.: To be sure the issue doesn't fall through the cracks unnoticed,
I'm adding it to regzbot, the Linux kernel regression tracking bot:

#regzbot report /
#regzbot introduced 22a9d9585812440211b
#regzbot duplicate: https://lore.kernel.org/lkml/ZYhQ2-OnjDgoqjvt@wens.tw/
#regzbot title dmaengine: CPU stalls while loading bluetooth module
#regzbot ignore-activity