tree 51b538d1463c37a596a8b34dd81845861d2b8ee8
parent 718be4aaf3613cf7c2d097f925abc3d3553c0605
author Len Brown <len.brown@intel.com> 1279833790 -0400
committer Len Brown <len.brown@intel.com> 1279833790 -0400

ACPI: create "processor.bm_check_disable" boot param

processor.bm_check_disable=1" prevents Linux from checking BM_STS
before entering C3-type cpu power states.

This may be useful for a system running acpi_idle
where the BIOS exports FADT C-states, _CST IO C-states,
or _CST FFH C-states with the BM_STS bit set;
while configuring the chipset to set BM_STS
more frequently than perhaps is optimal.

Note that such systems may have been developed
using a tickful OS that would quickly clear BM_STS,
rather than a tickless OS that may go for some time
between checking and clearing BM_STS.

Note also that an alternative for newer systems
is to use the intel_idle driver, which always
ignores BM_STS, relying Linux device drivers
to register constraints explicitly via PM_QOS.

https://bugzilla.kernel.org/show_bug.cgi?id=15886

Signed-off-by: Len Brown <len.brown@intel.com>