Re: [PATCH 2/2] arm: disable frequency invariance for CONFIG_BL_SWITCHER

[Viresh Kumar]

On 24-09-20, 13:30, Ionela Voinescu wrote:
> big.LITTLE switching complicates the setting of a correct cpufreq-based
> frequency invariance scale factor due to (as observed in
> drivers/cpufreq/vexpress-spc-cpufreq.c):
>  - Incorrect current and maximum frequencies as a result of the
>    exposure of a virtual frequency table to the cpufreq core,
>  - Missed updates as a result of asynchronous frequency adjustments
>    caused by frequency changes in other CPU pairs.
> 
> Given that its functionality is atypical in regards to frequency
> invariance and this is an old technology, disable frequency
> invariance for when big.LITTLE switching is configured in to prevent
> incorrect scale setting.
> 
> Signed-off-by: Ionela Voinescu <ionela.voinescu@xxxxxxx>
> Suggested-by: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
> Cc: Russell King <linux@xxxxxxxxxxxxxxx>
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> ---
>  arch/arm/include/asm/topology.h | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/arm/include/asm/topology.h b/arch/arm/include/asm/topology.h
> index e5e3d5ce4d55..470299ee2fba 100644
> --- a/arch/arm/include/asm/topology.h
> +++ b/arch/arm/include/asm/topology.h
> @@ -7,10 +7,13 @@
>  #include <linux/cpumask.h>
>  #include <linux/arch_topology.h>
>  
> +/* big.LITTLE switcher is incompatible with frequency invariance */
> +#ifndef CONFIG_BL_SWITCHER
>  /* Replace task scheduler's default frequency-invariant accounting */
>  #define arch_set_freq_scale topology_set_freq_scale
>  #define arch_scale_freq_capacity topology_get_freq_scale
>  #define arch_scale_freq_invariant topology_scale_freq_invariant
> +#endif
>  
>  /* Replace task scheduler's default cpu-invariant accounting */
>  #define arch_scale_cpu_capacity topology_get_cpu_scale

Acked-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>

-- 
viresh