diff options
| author | Len Brown <len.brown@intel.com> | 2010-07-22 22:54:27 +0200 |
|---|---|---|
| committer | Len Brown <len.brown@intel.com> | 2010-07-22 22:54:27 +0200 |
| commit | 718be4aaf3613cf7c2d097f925abc3d3553c0605 (patch) | |
| tree | feaf57a034684a6742198a5cf10e8e05ed1cb10f /drivers/acpi/processor_idle.c | |
| parent | Merge branch 'drm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/air... (diff) | |
| download | linux-718be4aaf3613cf7c2d097f925abc3d3553c0605.tar.xz 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 'drivers/acpi/processor_idle.c')
| -rw-r--r-- | drivers/acpi/processor_idle.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c index b1b385692f46..b351342f1faf 100644 --- a/drivers/acpi/processor_idle.c +++ b/drivers/acpi/processor_idle.c @@ -947,7 +947,7 @@ static int acpi_idle_enter_bm(struct cpuidle_device *dev, if (acpi_idle_suspend) return(acpi_idle_enter_c1(dev, state)); - if (acpi_idle_bm_check()) { + if (!cx->bm_sts_skip && acpi_idle_bm_check()) { if (dev->safe_state) { dev->last_state = dev->safe_state; return dev->safe_state->enter(dev, dev->safe_state); |