[CPUFREQ] Processor Clocking Control interface driver

Processor Clocking Control (PCC) is an interface between the BIOS and OSPM.
Based on the server workload, OSPM can request what frequency it expects
from a logical CPU, and the BIOS will achieve that frequency transparently.

This patch introduces driver support for PCC. OSPM uses the PCC driver to
communicate with the BIOS via the PCC interface.

There is a Documentation file that provides a link to the PCC
Specification, and also provides a summary of the PCC interface.

Currently, certain HP ProLiant platforms implement the PCC interface. However,
any platform whose BIOS implements the PCC Specification, can utilize this
driver.

V2 --> V1 changes (based on Dominik's suggestions):
- Removed the dependency on CPU_FREQ_TABLE
- "cpufreq_stats" will no longer PANIC. Actually, it will not load anymore
because it is not applicable.
- Removed the sanity check for target frequency in the ->target routine.

NOTE: A patch to sanitize the target frequency requested by "ondemand" is
needed to ensure that the target freq < policy->min.

Can this driver be queued up for the 2.6.33 tree?

Signed-off-by: Naga Chumbalkar <nagananda.chumbalkar@hp.com>
Signed-off-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Dave Jones <davej@redhat.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/arch/x86/kernel/cpu/cpufreq/Kconfig b/arch/x86/kernel/cpu/cpufreq/Kconfig
index f138c6c389b9..870e6cc6ad28 100644
--- a/arch/x86/kernel/cpu/cpufreq/Kconfig
+++ b/arch/x86/kernel/cpu/cpufreq/Kconfig
@@ -10,6 +10,20 @@ if CPU_FREQ
 
 comment "CPUFreq processor drivers"
 
+config X86_PCC_CPUFREQ
+        tristate "Processor Clocking Control interface driver"
+        depends on ACPI && ACPI_PROCESSOR
+        help
+          This driver adds support for the PCC interface.
+
+          For details, take a look at:
+          <file:Documentation/cpu-freq/pcc-cpufreq.txt>.
+
+          To compile this driver as a module, choose M here: the
+          module will be called pcc-cpufreq.
+
+          If in doubt, say N.
+
 config X86_ACPI_CPUFREQ
         tristate "ACPI Processor P-States driver"
         select CPU_FREQ_TABLE