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| author | Len Brown <len.brown@intel.com> | 2010-07-22 16:54:27 -0400 |
|---|---|---|
| committer | Len Brown <len.brown@intel.com> | 2010-07-22 16:54:27 -0400 |
| commit | 718be4aaf3613cf7c2d097f925abc3d3553c0605 (patch) | |
| tree | feaf57a034684a6742198a5cf10e8e05ed1cb10f /lib/locking-selftest.c | |
| parent | f4b23cc2d5dc78ef5acbc529eb1219cc41eb5b96 (diff) | |
| download | blackbird-obmc-linux-718be4aaf3613cf7c2d097f925abc3d3553c0605.tar.gz blackbird-obmc-linux-718be4aaf3613cf7c2d097f925abc3d3553c0605.zip | |
ACPI: skip checking BM_STS if the BIOS doesn't ask for it
It turns out that there is a bit in the _CST for Intel FFH C3
that tells the OS if we should be checking BM_STS or not.
Linux has been unconditionally checking BM_STS.
If the chip-set is configured to enable BM_STS,
it can retard or completely prevent entry into
deep C-states -- as illustrated by turbostat:
http://userweb.kernel.org/~lenb/acpi/utils/pmtools/turbostat/
ref: Intel Processor Vendor-Specific ACPI Interface Specification
table 4 "_CST FFH GAS Field Encoding"
Bit 1: Set to 1 if OSPM should use Bus Master avoidance for this C-state
https://bugzilla.kernel.org/show_bug.cgi?id=15886
Signed-off-by: Len Brown <len.brown@intel.com>
Diffstat (limited to 'lib/locking-selftest.c')
0 files changed, 0 insertions, 0 deletions
