Re: [PATCH v1] ASoC: meson: axg-fifo: set option to use raw spinlock

[Jerome Brunet <jbrunet@baylibre.com>]

On Mon 29 Jul 2024 at 16:28, Mark Brown <broonie@kernel.org> wrote:

> On Mon, Jul 29, 2024 at 05:06:50PM +0200, Jerome Brunet wrote:
>> On Mon 29 Jul 2024 at 15:44, Mark Brown <broonie@kernel.org> wrote:
>
>> > I don't recall this coming up much TBH.  It may be that people just set
>> > raw spinlocks when they need it, or that there's not many people using
>> > relevant devices with RT kernels.
>
>> I have not been playing much with RT TBH, but AFAIK, with RT irq
>> handlers are threaded unless IRQF_NO_THREAD is set. In this case,
>> something preemptible in the handler should not be a problem.
>
>> The axg-fifo drivers do not have IRQF_NO_THREAD so something is a bit
>> unclear here.
>
> Yeah, it's definitely likely to happen all the time for people using RT
> with relevant devices.  I'm not sure I have a good sense of if it's
> likely to be a nasty surprise to switch raw spinlocks on by default when
> it's currently controllable, I'd expect it'll generally be fine but it's
> possibly a bit rude to any users that don't use interrupts...

Indeed it is bit radical.

My concern with this patch is that, IIUC, the handler should be
threaded under RT and there should be no problem with the spinlock API.

Adding the RT folks to try to get a better understanding, they should
have been CCed anyway.

-- 
Jerome