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

Théo Lebrun
2024-04-08T14:42:46Z

Hello,

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:
>
> > If the CQSPI_BUSYWAIT_EARLY quirk flag is on, call
> > readl_relaxed_poll_timeout() with no sleep at the start of
> > cqspi_wait_for_bit(). If its short timeout expires, a sleeping
> > readl_relaxed_poll_timeout() call takes the relay.
> >
> > Behavior is hidden behind a quirk flag to keep the previous behavior the
> > same on all platforms.
> >
> > 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.

Regards,

--
Théo Lebrun, Bootlin
Embedded Linux and Kernel engineering