acpi-cpufreq: Add new sysfs attribute freqdomain_cpus

Commits fcf8058 (cpufreq: Simplify cpufreq_add_dev()) and aa77a52
(cpufreq: acpi-cpufreq: Don't set policy->related_cpus from .init())
changed the contents of the "related_cpus" sysfs attribute on systems
where acpi-cpufreq is used and user space can't get the list of CPUs
which are in the same hardware coordination CPU domain (provided by
the ACPI AML method _PSD) via "related_cpus" any more.

To make up for that loss add a new sysfs attribute "freqdomian_cpus"
for the acpi-cpufreq driver which exposes the list of CPUs in the
same domain regardless of whether it is coordinated by hardware or
software.

[rjw: Changelog, documentation]
References: https://bugzilla.kernel.org/show_bug.cgi?id=58761
Reported-by: Jean-Philippe Halimi <jean-philippe.halimi@exascale-computing.eu>
Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

4 files changed, 44 insertions, 4 deletions

diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index 2447698aed41..468e4d48f884 100644
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -144,6 +144,21 @@ Description:	Discover and change clock speed of CPUs
                 to learn how to control the knobs.
 
 
+What:           /sys/devices/system/cpu/cpu#/cpufreq/freqdomain_cpus
+Date:           June 2013
+Contact:        cpufreq@vger.kernel.org
+Description:    Discover CPUs in the same CPU frequency coordination domain
+
+                freqdomain_cpus is the list of CPUs (online+offline) that share
+                the same clock/freq domain (possibly at the hardware level).
+                That information may be hidden from the cpufreq core and the
+                value of related_cpus may be different from freqdomain_cpus. This
+                attribute is useful for user space DVFS controllers to get better
+                power/performance results for platforms using acpi-cpufreq.
+
+                This file is only present if the acpi-cpufreq driver is in use.
+
+
 What:           /sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1}
 Date:           August 2008
 KernelVersion:  2.6.27
diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
index 2c5906d71397..403dad646abe 100644
--- a/drivers/cpufreq/acpi-cpufreq.c
+++ b/drivers/cpufreq/acpi-cpufreq.c
@@ -70,6 +70,7 @@ struct acpi_cpufreq_data {
         struct cpufreq_frequency_table *freq_table;
         unsigned int resume;
         unsigned int cpu_feature;
+        cpumask_var_t freqdomain_cpus;
 };
 
 static DEFINE_PER_CPU(struct acpi_cpufreq_data *, acfreq_data);
@@ -176,6 +177,15 @@ static struct global_attr global_boost = __ATTR(boost, 0644,
                                                 show_global_boost,
                                                 store_global_boost);
 
+static ssize_t show_freqdomain_cpus(struct cpufreq_policy *policy, char *buf)
+{
+        struct acpi_cpufreq_data *data = per_cpu(acfreq_data, policy->cpu);
+
+        return cpufreq_show_cpus(data->freqdomain_cpus, buf);
+}
+
+cpufreq_freq_attr_ro(freqdomain_cpus);
+
 #ifdef CONFIG_X86_ACPI_CPUFREQ_CPB
 static ssize_t store_cpb(struct cpufreq_policy *policy, const char *buf,
                          size_t count)
@@ -704,6 +714,11 @@ static int acpi_cpufreq_cpu_init(struct cpufreq_policy *policy)
         if (!data)
                 return -ENOMEM;
 
+        if (!zalloc_cpumask_var(&data->freqdomain_cpus, GFP_KERNEL)) {
+                result = -ENOMEM;
+                goto err_free;
+        }
+
         data->acpi_data = per_cpu_ptr(acpi_perf_data, cpu);
         per_cpu(acfreq_data, cpu) = data;
 
@@ -712,7 +727,7 @@ static int acpi_cpufreq_cpu_init(struct cpufreq_policy *policy)
 
         result = acpi_processor_register_performance(data->acpi_data, cpu);
         if (result)
-                goto err_free;
+                goto err_free_mask;
 
         perf = data->acpi_data;
         policy->shared_type = perf->shared_type;
@@ -725,6 +740,7 @@ static int acpi_cpufreq_cpu_init(struct cpufreq_policy *policy)
             policy->shared_type == CPUFREQ_SHARED_TYPE_ANY) {
                 cpumask_copy(policy->cpus, perf->shared_cpu_map);
         }
+        cpumask_copy(data->freqdomain_cpus, perf->shared_cpu_map);
 
 #ifdef CONFIG_SMP
         dmi_check_system(sw_any_bug_dmi_table);
@@ -736,6 +752,7 @@ static int acpi_cpufreq_cpu_init(struct cpufreq_policy *policy)
         if (check_amd_hwpstate_cpu(cpu) && !acpi_pstate_strict) {
                 cpumask_clear(policy->cpus);
                 cpumask_set_cpu(cpu, policy->cpus);
+                cpumask_copy(data->freqdomain_cpus, cpu_sibling_mask(cpu));
                 policy->shared_type = CPUFREQ_SHARED_TYPE_HW;
                 pr_info_once(PFX "overriding BIOS provided _PSD data\n");
         }
@@ -870,6 +887,8 @@ err_freqfree:
         kfree(data->freq_table);
 err_unreg:
         acpi_processor_unregister_performance(perf, cpu);
+err_free_mask:
+        free_cpumask_var(data->freqdomain_cpus);
 err_free:
         kfree(data);
         per_cpu(acfreq_data, cpu) = NULL;
@@ -888,6 +907,7 @@ static int acpi_cpufreq_cpu_exit(struct cpufreq_policy *policy)
                 per_cpu(acfreq_data, policy->cpu) = NULL;
                 acpi_processor_unregister_performance(data->acpi_data,
                                                       policy->cpu);
+                free_cpumask_var(data->freqdomain_cpus);
                 kfree(data->freq_table);
                 kfree(data);
         }
@@ -908,6 +928,7 @@ static int acpi_cpufreq_resume(struct cpufreq_policy *policy)
 
 static struct freq_attr *acpi_cpufreq_attr[] = {
         &cpufreq_freq_attr_scaling_available_freqs,
+        &freqdomain_cpus,
         NULL,   /* this is a placeholder for cpb, do not remove */
         NULL,
 };
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 03b3b69f64a7..6a015ada5285 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -585,7 +585,7 @@ out:
         return i;
 }
 
-static ssize_t show_cpus(const struct cpumask *mask, char *buf)
+ssize_t cpufreq_show_cpus(const struct cpumask *mask, char *buf)
 {
         ssize_t i = 0;
         unsigned int cpu;
@@ -600,6 +600,7 @@ static ssize_t show_cpus(const struct cpumask *mask, char *buf)
         i += sprintf(&buf[i], "\n");
         return i;
 }
+EXPORT_SYMBOL_GPL(cpufreq_show_cpus);
 
 /**
  * show_related_cpus - show the CPUs affected by each transition even if
@@ -607,7 +608,7 @@ static ssize_t show_cpus(const struct cpumask *mask, char *buf)
  */
 static ssize_t show_related_cpus(struct cpufreq_policy *policy, char *buf)
 {
-        return show_cpus(policy->related_cpus, buf);
+        return cpufreq_show_cpus(policy->related_cpus, buf);
 }
 
 /**
@@ -615,7 +616,7 @@ static ssize_t show_related_cpus(struct cpufreq_policy *policy, char *buf)
  */
 static ssize_t show_affected_cpus(struct cpufreq_policy *policy, char *buf)
 {
-        return show_cpus(policy->cpus, buf);
+        return cpufreq_show_cpus(policy->cpus, buf);
 }
 
 static ssize_t store_scaling_setspeed(struct cpufreq_policy *policy,
diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index c0bc7374445e..4d7390bc1727 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -439,4 +439,7 @@ void cpufreq_frequency_table_get_attr(struct cpufreq_frequency_table *table,
 void cpufreq_frequency_table_update_policy_cpu(struct cpufreq_policy *policy);
 
 void cpufreq_frequency_table_put_attr(unsigned int cpu);
+
+ssize_t cpufreq_show_cpus(const struct cpumask *mask, char *buf);
+
 #endif /* _LINUX_CPUFREQ_H */