Re: [PATCH 13/15] powerpc/rtas: Use fsleep() to minimize additional sleep duration

Michael Ellerman
2024-09-05T12:24:07Z

Anna-Maria Behnsen <anna-maria@linutronix.de> writes:
> When commit 38f7b7067dae ("powerpc/rtas: rtas_busy_delay() improvements")
> was introduced, documentation about proper usage of sleep realted functions
> was outdated.
>
...
> Use fsleep() directly instead of using an own heuristic for the best
> sleeping mechanism to use..

Thanks for tidying this up. I only learnt about fsleep() in the last ~year.

Two minor nits ...

> diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
> index f7e86e09c49f..0794ca28e51e 100644
> --- a/arch/powerpc/kernel/rtas.c
> +++ b/arch/powerpc/kernel/rtas.c
> @@ -1390,21 +1390,14 @@ bool __ref rtas_busy_delay(int status)
> */
> ms = clamp(ms, 1U, 1000U);
> /*
> - * The delay hint is an order-of-magnitude suggestion, not
> - * a minimum. It is fine, possibly even advantageous, for
> - * us to pause for less time than hinted. For small values,
> - * use usleep_range() to ensure we don't sleep much longer
> - * than actually needed.
> - *
> - * See Documentation/timers/timers-howto.rst for
> - * explanation of the threshold used here. In effect we use
> - * usleep_range() for 9900 and 9901, msleep() for
> - * 9902-9905.
> + * The delay hint is an order-of-magnitude suggestion, not a
> + * minimum. It is fine, possibly even advantageous, for us to
> + * pause for less time than hinted. To make sure pause time will
> + * not be a way longer than requested independent of HZ

"not be way longer" reads better I think?

> + * configuration, use fsleep(). See fsleep() for detailes of
^
details
> + * used sleeping functions.
> */
> - if (ms <= 20)
> - usleep_range(ms * 100, ms * 1000);
> - else
> - msleep(ms);
> + fsleep(ms * 1000);
> break;
> case RTAS_BUSY:
> ret = true;

Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)

cheers