On 22-02-21, 16:57, Rafael J. Wysocki wrote:
> On Mon, Feb 22, 2021 at 12:20 PM Viresh Kumar <viresh.ku...@linaro.org> wrote:
> Even though the driver is located in drivers/cpufreq/ CPPC is part of
> ACPI and so a CC to linux-acpi is missing.
I just used get-maintainers, perhaps we should add an entry for this
in MAINTAINERS, will be orphan though..
> > diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
> > index e65e0a43be64..a3e2d6dfea70 100644
> > --- a/drivers/cpufreq/Kconfig.arm
> > +++ b/drivers/cpufreq/Kconfig.arm
> > @@ -19,6 +19,15 @@ config ACPI_CPPC_CPUFREQ
> >
> > If in doubt, say N.
> >
> > +config ACPI_CPPC_CPUFREQ_FIE
> > + bool "Frequency Invariance support for CPPC cpufreq driver"
> > + depends on ACPI_CPPC_CPUFREQ
>
> In theory, the CPPC cpufreq driver can be used on systems with
> nontrivial arch_freq_scale_tick() in which case the latter should be
> used I suppose.
>
> Would that actually happen if this option is enabled?
IIUC, you are saying that if this driver runs on x86 then we want
arch_freq_scale_tick() from arch/x86/kernel/smpboot.c to run instead
of this ? Yes that will happen because x86 doesn't enable
CONFIG_GENERIC_ARCH_TOPOLOGY and so this code will never trigger.
For other cases, like ARM AMU counters, the arch specific
implementation takes precedence to this.
> > +static void __init cppc_freq_invariance_init(void)
> > +{
> > + struct cppc_perf_fb_ctrs fb_ctrs = {0};
> > + struct cppc_freq_invariance *cppc_fi;
> > + struct sched_attr attr = {
> > + .size = sizeof(struct sched_attr),
> > + .sched_policy = SCHED_DEADLINE,
> > + .sched_nice = 0,
> > + .sched_priority = 0,
> > + /*
> > + * Fake (unused) bandwidth; workaround to "fix"
> > + * priority inheritance.
> > + */
> > + .sched_runtime = 1000000,
> > + .sched_deadline = 10000000,
> > + .sched_period = 10000000,
> > + };
> > + int i, ret;
> > +
> > + if (cppc_cpufreq_driver.get == hisi_cppc_cpufreq_get_rate)
> > + return;
> > +
> > + kworker_fie = kthread_create_worker(0, "cppc_fie");
> > + if (IS_ERR(kworker_fie))
> > + return;
> > +
> > + for_each_possible_cpu(i) {
> > + cppc_fi = &per_cpu(cppc_freq_inv, i);
> > +
> > + /* A policy failed to initialize, abort */
> > + if (unlikely(!cppc_fi->cpu_data))
> > + return cppc_freq_invariance_exit();
> > +
> > + kthread_init_work(&cppc_fi->work, cppc_scale_freq_workfn);
> > + init_irq_work(&cppc_fi->irq_work, cppc_irq_work);
>
> What would be wrong with doing the above in
> cppc_freq_invariance_policy_init()? It looks like a better place to
> me.
Can move it there as well, I just kept policy specific stuff there as
ideally I wanted to do everything here.
> > + ret = sched_setattr_nocheck(kworker_fie->task, &attr);
>
> And this needs to be done only once if I'm not mistaken.
Yes, I failed to fix this when I went to a single kworker.
--
viresh
