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, 12 insertions, 0 deletions

diff --git a/drivers/cpufreq/Kconfig.x86 b/drivers/cpufreq/Kconfig.x86
index b36ca1f68bff..934854ae5eb4 100644
--- a/drivers/cpufreq/Kconfig.x86
+++ b/drivers/cpufreq/Kconfig.x86
@@ -33,6 +33,18 @@ config X86_ACPI_CPUFREQ
 
           If in doubt, say N.
 
+config X86_ACPI_CPUFREQ_CPB
+        default y
+        bool "Legacy cpb sysfs knob support for AMD CPUs"
+        depends on X86_ACPI_CPUFREQ && CPU_SUP_AMD
+        help
+          The powernow-k8 driver used to provide a sysfs knob called "cpb"
+          to disable the Core Performance Boosting feature of AMD CPUs. This
+          file has now been superseeded by the more generic "boost" entry.
+
+          By enabling this option the acpi_cpufreq driver provides the old
+          entry in addition to the new boost ones, for compatibility reasons.
+
 config ELAN_CPUFREQ
         tristate "AMD Elan SC400 and SC410"
         select CPU_FREQ_TABLE