Messages in this thread | | | Subject | Re: [PATCH v2 3/7] arch_topology: disable frequency invariance for CONFIG_BL_SWITCHER | From | Dietmar Eggemann <> | Date | Thu, 30 Jul 2020 12:29:52 +0200 |
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On 30/07/2020 06:24, Viresh Kumar wrote: > On 22-07-20, 10:37, Ionela Voinescu wrote: >> +++ b/drivers/base/arch_topology.c >> @@ -27,6 +27,7 @@ __weak bool arch_freq_counters_available(struct cpumask *cpus) >> } >> DEFINE_PER_CPU(unsigned long, freq_scale) = SCHED_CAPACITY_SCALE; >> >> +#ifndef CONFIG_BL_SWITCHER >> void arch_set_freq_scale(struct cpumask *cpus, unsigned long cur_freq, >> unsigned long max_freq) >> { >> @@ -46,6 +47,7 @@ void arch_set_freq_scale(struct cpumask *cpus, unsigned long cur_freq, >> for_each_cpu(i, cpus) >> per_cpu(freq_scale, i) = scale; >> } >> +#endif > > I don't really like this change, the ifdef hackery is disgusting and > then we are putting that in a completely different part of the kernel. > > There are at least these two ways of solving this, maybe more: > > - Fix the bl switcher driver and add the complexity in it (which you > tried to do earlier). > > - Add a cpufreq flag to skip arch-set-freq-scale call.
I agree it's not nice but IMHO the cpufreq flag is worse since we would introduce new infrastructure only for a deprecated feature. I'm assuming that BL SWITCHER is the only feature needing this CPUfreq flag extension.
#ifdef CONFIG_BL_SWITCHER is already in drivers/irqchip/irq-gic.c so it's ugly already.
Runtime detecting (via bL_switching_enabled) of BL SWITCHER is right now also only handled inside vexpress-spc-cpufreq.c via a bL_switcher_notifier. A mechanism which also sits behind a #ifdef CONFIG_BL_SWITCHER.
So IMHO, the additional #ifdef CONFIG_BL_SWITCHER in drivers/base/arch_topology.c it's a small price to pay.
Are there still any users of CONFIG_BL_SWITCHER? I guess it's only limited to A15/A7 systems w/ vexpress-spc-cpufreq.c ... so probably only TC2?
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