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Subject[095/111] ACPI: Fix regression where _PPC is not read at boot even when ignore_ppc=0
2.6.32-stable review patch.  If anyone has any objections, please let us know.


From: Darrick J. Wong <>

commit 455c0d71d46e86b0b7ff2c9dcfc19bc162302ee9 upstream.

Earlier, Ingo Molnar posted a patch to make it so that the kernel would avoid
reading _PPC on his broken T60. Unfortunately, it seems that with Thomas
Renninger's patch last July to eliminate _PPC evaluations when the processor
driver loads, the kernel never actually reads _PPC at all! This is problematic
if you happen to boot your non-T60 computer in a state where the BIOS _wants_
_PPC to be something other than zero.

So, put the _PPC evaluation back into acpi_processor_get_performance_info if
ignore_ppc isn't 1.

Signed-off-by: Darrick J. Wong <>
Signed-off-by: Len Brown <>
Acked-by: Jeff Mahoney <>
Signed-off-by: Greg Kroah-Hartman <>

drivers/acpi/processor_perflib.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

--- a/drivers/acpi/processor_perflib.c
+++ b/drivers/acpi/processor_perflib.c
@@ -356,7 +356,11 @@ static int acpi_processor_get_performanc
if (result)
goto update_bios;

- return 0;
+ /* We need to call _PPC once when cpufreq starts */
+ if (ignore_ppc != 1)
+ result = acpi_processor_get_platform_limit(pr);
+ return result;

* Having _PPC but missing frequencies (_PSS, _PCT) is a very good hint that

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