Re: [PATCH v2 18/20] mips: csrc-r4k: Decrease r4k-clocksource rating if CPU_FREQ enabled

Thomas Bogendoerfer
2020-05-08T15:42:37Z

On Wed, May 06, 2020 at 08:42:36PM +0300, Sergey.Semin@baikalelectronics.ru wrote:
> From: Serge Semin <Sergey.Semin@baikalelectronics.ru>
>
> Commit 07d69579e7fe ("MIPS: Don't register r4k sched clock when
> CPUFREQ enabled") disabled the r4k-clock usage for scheduler ticks
> counting due to the scheduler being non-tolerant for unstable
> clocks sources. For the same reason the clock should be used
> in the system clocksource framework only as a last resort if CPU
> frequency may change.
>
> Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
> Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
> Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
> Cc: Paul Burton <paulburton@kernel.org>
> Cc: Ralf Baechle <ralf@linux-mips.org>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Rob Herring <robh+dt@kernel.org>
> Cc: linux-pm@vger.kernel.org
> Cc: devicetree@vger.kernel.org
> ---
> arch/mips/kernel/csrc-r4k.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/arch/mips/kernel/csrc-r4k.c b/arch/mips/kernel/csrc-r4k.c
> index 437dda64fd7a..d81fb374f477 100644
> --- a/arch/mips/kernel/csrc-r4k.c
> +++ b/arch/mips/kernel/csrc-r4k.c
> @@ -71,7 +71,11 @@ int __init init_r4k_clocksource(void)
> return -ENXIO;
>
> /* Calculate a somewhat reasonable rating value */
> +#ifndef CONFIG_CPU_FREQ
> clocksource_mips.rating = 200 + mips_hpt_frequency / 10000000;
> +#else
> + clocksource_mips.rating = 99;
> +#endif

I dislike this patch. Assuming you have an other clocksource, why not
simply disable csrc-r4k, if CPU_FREQ is enabled ?

Thomas.

--
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