acpi-cpufreq: Add compatibility for legacy AMD cpb sysfs knob

The powernow-k8 driver supported a sysfs knob called "cpb", which was
instantiated per CPU, but actually acted globally for the whole
system. To keep some compatibility with this feature, we re-introduce
this behavior here, but:
a) only enable it on AMD CPUs and
b) protect it with a Kconfig switch

I'd like to consider this feature obsolete. Lets keep it around for
some kernel versions and then phase it out.

Signed-off-by: Andre Przywara <andre.przywara@amd.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

1 files changed, 44 insertions, 2 deletions

diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
index dffa7af1db71..0d048f6a2b23 100644
--- a/drivers/cpufreq/acpi-cpufreq.c
+++ b/drivers/cpufreq/acpi-cpufreq.c
@@ -133,8 +133,7 @@ static void boost_set_msrs(bool enable, const struct cpumask *cpumask)
         wrmsr_on_cpus(cpumask, msr_addr, msrs);
 }
 
-static ssize_t store_global_boost(struct kobject *kobj, struct attribute *attr,
-                                  const char *buf, size_t count)
+static ssize_t _store_boost(const char *buf, size_t count)
 {
         int ret;
         unsigned long val = 0;
@@ -161,6 +160,12 @@ static ssize_t store_global_boost(struct kobject *kobj, struct attribute *attr,
         return count;
 }
 
+static ssize_t store_global_boost(struct kobject *kobj, struct attribute *attr,
+                                  const char *buf, size_t count)
+{
+        return _store_boost(buf, count);
+}
+
 static ssize_t show_global_boost(struct kobject *kobj,
                                  struct attribute *attr, char *buf)
 {
@@ -171,6 +176,21 @@ static struct global_attr global_boost = __ATTR(boost, 0644,
                                                 show_global_boost,
                                                 store_global_boost);
 
+#ifdef CONFIG_X86_ACPI_CPUFREQ_CPB
+static ssize_t store_cpb(struct cpufreq_policy *policy, const char *buf,
+                         size_t count)
+{
+        return _store_boost(buf, count);
+}
+
+static ssize_t show_cpb(struct cpufreq_policy *policy, char *buf)
+{
+        return sprintf(buf, "%u\n", boost_enabled);
+}
+
+static struct freq_attr cpb = __ATTR(cpb, 0644, show_cpb, store_cpb);
+#endif
+
 static int check_est_cpu(unsigned int cpuid)
 {
         struct cpuinfo_x86 *cpu = &cpu_data(cpuid);
@@ -889,6 +909,7 @@ static int acpi_cpufreq_resume(struct cpufreq_policy *policy)
 
 static struct freq_attr *acpi_cpufreq_attr[] = {
         &cpufreq_freq_attr_scaling_available_freqs,
+        NULL,   /* this is a placeholder for cpb, do not remove */
         NULL,
 };
 
@@ -960,6 +981,27 @@ static int __init acpi_cpufreq_init(void)
         if (ret)
                 return ret;
 
+#ifdef CONFIG_X86_ACPI_CPUFREQ_CPB
+        /* this is a sysfs file with a strange name and an even stranger
+         * semantic - per CPU instantiation, but system global effect.
+         * Lets enable it only on AMD CPUs for compatibility reasons and
+         * only if configured. This is considered legacy code, which
+         * will probably be removed at some point in the future.
+         */
+        if (check_amd_hwpstate_cpu(0)) {
+                struct freq_attr **iter;
+
+                pr_debug("adding sysfs entry for cpb\n");
+
+                for (iter = acpi_cpufreq_attr; *iter != NULL; iter++)
+                        ;
+
+                /* make sure there is a terminator behind it */
+                if (iter[1] == NULL)
+                        *iter = &cpb;
+        }
+#endif
+
         ret = cpufreq_register_driver(&acpi_cpufreq_driver);
         if (ret)
                 free_acpi_perf_data();