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

[Thomas Bogendoerfer]

On Wed, May 06, 2020 at 08:42:36PM +0300, Sergey.Semin@xxxxxxxxxxxxxxxxxxxx wrote:
> From: Serge Semin <Sergey.Semin@xxxxxxxxxxxxxxxxxxxx>
> 
> 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@xxxxxxxxxxxxxxxxxxxx>
> Cc: Alexey Malahov <Alexey.Malahov@xxxxxxxxxxxxxxxxxxxx>
> Cc: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>
> Cc: Paul Burton <paulburton@xxxxxxxxxx>
> Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>
> Cc: Rob Herring <robh+dt@xxxxxxxxxx>
> Cc: linux-pm@xxxxxxxxxxxxxxx
> Cc: devicetree@xxxxxxxxxxxxxxx
> ---
>  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.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]