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Date: Mon, 20 Jul 2015 14:08:24 -0700
From: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
To: Konstantin Khlebnikov <koct9i@...il.com>
Cc: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
linux-pm@...r.kernel.org, "Rafael J. Wysocki" <rjw@...ysocki.net>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
linux-acpi@...r.kernel.org,
Kristen Carlson Accardi <kristen@...ux.intel.com>,
Len Brown <lenb@...nel.org>, Ethan Zhao <ethan.zhao@...cle.com>
Subject: Re: [PATCH RFC] intel_pstate: play well with frequency limits set
by acpi
On Fri, 2015-07-17 at 07:36 +0300, Konstantin Khlebnikov wrote:
> On Fri, Jul 17, 2015 at 1:08 AM, Srinivas Pandruvada
> <srinivas.pandruvada@...ux.intel.com> wrote:
> > On Thu, 2015-07-16 at 21:17 +0300, Konstantin Khlebnikov wrote:
> >> IPMI can control CPU P-states remotely: configuration is reported via
> >> common ACPI interface (_PPC/_PSS/etc). This patch adds required minimal
> >> support in intel_pstate to receive and use these P-state limits.
> >>
> >> * ignore limit of top state in _PPC: it lower than turbo boost frequency
> >> * register intel_pstate in acpi-processor to get states from _PSS
> >> * link acpi_processor_get_bios_limit: this adds attribute "bios_limit"
> >>
> >> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
> >> ---
> >> drivers/acpi/processor_perflib.c | 3 +-
> >> drivers/cpufreq/intel_pstate.c | 57 ++++++++++++++++++++++++++++++++++++++
> >> 2 files changed, 59 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/acpi/processor_perflib.c b/drivers/acpi/processor_perflib.c
> >> index cfc8aba72f86..781e328c9d5f 100644
> >> --- a/drivers/acpi/processor_perflib.c
> >> +++ b/drivers/acpi/processor_perflib.c
> >> @@ -98,7 +98,8 @@ static int acpi_processor_ppc_notifier(struct notifier_block *nb,
> >>
> >> ppc = (unsigned int)pr->performance_platform_limit;
> >>
> >> - if (ppc >= pr->performance->state_count)
> >> + /* Ignore limit of top state: it lower than turbo boost frequency */
> >> + if (!ppc || ppc >= pr->performance->state_count)
> > Why? Isn't the previous check enough?
>
> Zero _PPC state must be top performance state but as I see frequency in
> _PSS is lower than maximum possible turbo frequency. So, in this case
> intel_pstate cannnot get "100%" for max bound even it there is no limit set.
>
> For example: I saw _PSS[0] = 2601 Mhz, PSS[1] = 2600 Mhz while turbo
> state is 3400 Mhz.
>
Have you tested dynamic _PPC modification with acpi cpufreq with this
change (after boot)? Suppose _PPC is changed from 3 to 0, then
cpufreq_verify_within_limits will not be called to change to new max
turbo performance state.
Thanks,
Srinivas
> >> goto out;
> >>
> >> cpufreq_verify_within_limits(policy, 0,
> >> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
> >> index 15ada47bb720..4a34ddf4fa73 100644
> >> --- a/drivers/cpufreq/intel_pstate.c
> >> +++ b/drivers/cpufreq/intel_pstate.c
> >> @@ -26,6 +26,7 @@
> >> #include <linux/fs.h>
> >> #include <linux/debugfs.h>
> >> #include <linux/acpi.h>
> >> +#include <acpi/processor.h>
> >> #include <linux/vmalloc.h>
> >> #include <trace/events/power.h>
> >>
> >> @@ -113,6 +114,9 @@ struct cpudata {
> >> u64 prev_mperf;
> >> u64 prev_tsc;
> >> struct sample sample;
> >> +#ifdef CONFIG_ACPI_PROCESSOR
> >> + struct acpi_processor_performance acpi_data;
> >> +#endif
> >> };
> >>
> >> static struct cpudata **all_cpu_data;
> >> @@ -145,6 +149,7 @@ static int hwp_active;
> >>
> >> struct perf_limits {
> >> int no_turbo;
> >> + int no_acpi;
> >> int turbo_disabled;
> >> int max_perf_pct;
> >> int min_perf_pct;
> >> @@ -158,6 +163,7 @@ struct perf_limits {
> >>
> >> static struct perf_limits limits = {
> >> .no_turbo = 0,
> >> + .no_acpi = !IS_ENABLED(CONFIG_ACPI_PROCESSOR),
> >> .turbo_disabled = 0,
> >> .max_perf_pct = 100,
> >> .max_perf = int_tofp(1),
> >> @@ -449,6 +455,18 @@ static ssize_t store_min_perf_pct(struct kobject *a, struct attribute *b,
> >> return count;
> >> }
> >>
> >> +static ssize_t store_no_acpi(struct kobject *a, struct attribute *b,
> >> + const char *buf, size_t count)
> >> +{
> >> +#ifdef CONFIG_ACPI_PROCESSOR
> >> + return kstrtouint(buf, 0, &limits.no_acpi) ?: count;
> >> +#else
> >> + return -ENODEV;
> >> +#endif
> >> +}
> >> +show_one(no_acpi, no_acpi);
> >> +define_one_global_rw(no_acpi);
> >> +
> >> show_one(max_perf_pct, max_perf_pct);
> >> show_one(min_perf_pct, min_perf_pct);
> >>
> >> @@ -460,6 +478,7 @@ define_one_global_ro(num_pstates);
> >>
> >> static struct attribute *intel_pstate_attributes[] = {
> >> &no_turbo.attr,
> >> + &no_acpi.attr,
> >> &max_perf_pct.attr,
> >> &min_perf_pct.attr,
> >> &turbo_pct.attr,
> >> @@ -1049,6 +1068,38 @@ static int intel_pstate_cpu_init(struct cpufreq_policy *policy)
> >> policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
> >> cpumask_set_cpu(policy->cpu, policy->cpus);
> >>
> >> +#ifdef CONFIG_ACPI_PROCESSOR
> >> + if (!limits.no_acpi) {
> >> + /*
> >> + * Minimum necessary to get acpi_processor_ppc_notifier() and
> >> + * acpi_processor_get_bios_limit() working.
> >> + */
> >> + if (!zalloc_cpumask_var(&cpu->acpi_data.shared_cpu_map,
> >> + GFP_KERNEL))
> >> + rc = -ENOMEM;
> >> + else
> >> + rc = acpi_processor_register_performance(
> >> + &cpu->acpi_data, policy->cpu);
> >> + if (rc) {
> >> + pr_err("intel_pstate: acpi init failed: %d\n", rc);
> >> + free_cpumask_var(cpu->acpi_data.shared_cpu_map);
> >> + limits.no_acpi = 1;
> >> + }
> >> + }
> >> +#endif
> >> + return 0;
> >> +}
> >> +
> >> +static int intel_pstate_cpu_exit(struct cpufreq_policy *policy)
> >> +{
> >> +#ifdef CONFIG_ACPI_PROCESSOR
> >> + struct cpudata *cpu = all_cpu_data[policy->cpu];
> >> +
> >> + if (cpu->acpi_data.state_count)
> >> + acpi_processor_unregister_performance(&cpu->acpi_data,
> >> + policy->cpu);
> >> + free_cpumask_var(cpu->acpi_data.shared_cpu_map);
> >> +#endif
> >> return 0;
> >> }
> >>
> >> @@ -1057,7 +1108,11 @@ static struct cpufreq_driver intel_pstate_driver = {
> >> .verify = intel_pstate_verify_policy,
> >> .setpolicy = intel_pstate_set_policy,
> >> .get = intel_pstate_get,
> >> +#ifdef CONFIG_ACPI_PROCESSOR
> >> + .bios_limit = acpi_processor_get_bios_limit,
> >> +#endif
> >> .init = intel_pstate_cpu_init,
> >> + .exit = intel_pstate_cpu_exit,
> >> .stop_cpu = intel_pstate_stop_cpu,
> >> .name = "intel_pstate",
> >> };
> >> @@ -1286,6 +1341,8 @@ static int __init intel_pstate_setup(char *str)
> >> force_load = 1;
> >> if (!strcmp(str, "hwp_only"))
> >> hwp_only = 1;
> >> + if (!strcmp(str, "no_acpi"))
> >> + limits.no_acpi = 1;
> >> return 0;
> >> }
> >> early_param("intel_pstate", intel_pstate_setup);
> >>
> > _PPC is index into _PSS. Since intel P state doesn't follow _PSS, the
> > states may not be 1:1 matching. So we have to harmonize them.
> >
> >
> >> --
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> >
> >
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