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>

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

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,
 };

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,

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 */