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Subject[060/119] [CPUFREQ] Enable ACPI PDC handshake for VIA/Centaur CPUs
2.6.31-stable review patch.  If anyone has any objections, please let us know.

From: Harald Welte <>

commit d77b81974521c82fa6fda38dfff1b491dcc62a32 upstream.

In commit 0de51088e6a82bc8413d3ca9e28bbca2788b5b53, we introduced the
use of acpi-cpufreq on VIA/Centaur CPU's by removing a vendor check for
VENDOR_INTEL. However, as it turns out, at least the Nano CPU's also
need the PDC (processor driver capabilities) handshake in order to
activate the methods required for acpi-cpufreq.

Since arch_acpi_processor_init_pdc() contains another vendor check for
Intel, the PDC is not initialized on VIA CPU's. The resulting behavior
of a current mainline kernel on such systems is: acpi-cpufreq
loads and it indicates CPU frequency changes. However, the CPU stays at
a single frequency

This trivial patch ensures that init_intel_pdc() is called on Intel and
VIA/Centaur CPU's alike.

Signed-off-by: Harald Welte <>
Signed-off-by: Dave Jones <>
Signed-off-by: Greg Kroah-Hartman <>

arch/x86/kernel/acpi/processor.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/x86/kernel/acpi/processor.c
+++ b/arch/x86/kernel/acpi/processor.c
@@ -79,7 +79,8 @@ void arch_acpi_processor_init_pdc(struct
struct cpuinfo_x86 *c = &cpu_data(pr->id);

pr->pdc = NULL;
- if (c->x86_vendor == X86_VENDOR_INTEL)
+ if (c->x86_vendor == X86_VENDOR_INTEL ||
+ c->x86_vendor == X86_VENDOR_CENTAUR)
init_intel_pdc(pr, c);


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