Re: [PATCH v2 08/11] spi: cadence-qspi: add early busywait to cqspi_wait_for_bit()

Théo Lebrun
2024-04-09T10:09:26Z

Hello,

On Mon Apr 8, 2024 at 6:40 PM CEST, Mark Brown wrote:
> On Mon, Apr 08, 2024 at 04:42:43PM +0200, Théo Lebrun wrote:
> > On Mon Apr 8, 2024 at 4:16 PM CEST, Mark Brown wrote:
> > > On Fri, Apr 05, 2024 at 05:02:18PM +0200, Théo Lebrun wrote:
>
> > > > The reason is to avoid hrtimer interrupts on the system. All read
> > > > operations take less than 100µs.
>
> > > Why would this be platform specific, this seems like a very standard
> > > optimisation technique?
>
> > It does not make sense if you know that all read operations take more
> > than 100µs. I preferred being conservative. If you confirm it makes
> > sense I'll remove the quirk.
>
> It does seem plausible at least, and the time could be made a tuneable
> with quirks or otherwise if that's needed. I think I'd expect the MIPS
> platform you're working with to be towards the lower end of performance
> for systems that are new enough to have this hardware.

Next revision will do the same busywait behavior unconditionally then.

Thanks!

--
Théo Lebrun, Bootlin
Embedded Linux and Kernel engineering