diff options
| 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 | |
| parent | f4b23cc2d5dc78ef5acbc529eb1219cc41eb5b96 (diff) | |
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>
| -rw-r--r-- | arch/x86/kernel/acpi/cstate.c | 9 | ||||
| -rw-r--r-- | drivers/acpi/processor_idle.c | 2 | ||||
| -rw-r--r-- | include/acpi/processor.h | 3 |
3 files changed, 12 insertions, 2 deletions
diff --git a/arch/x86/kernel/acpi/cstate.c b/arch/x86/kernel/acpi/cstate.c index 2e837f5080fe..fb7a5f052e2b 100644 --- a/arch/x86/kernel/acpi/cstate.c +++ b/arch/x86/kernel/acpi/cstate.c @@ -145,6 +145,15 @@ int acpi_processor_ffh_cstate_probe(unsigned int cpu, percpu_entry->states[cx->index].eax = cx->address; percpu_entry->states[cx->index].ecx = MWAIT_ECX_INTERRUPT_BREAK; } + + /* + * For _CST FFH on Intel, if GAS.access_size bit 1 is cleared, + * then we should skip checking BM_STS for this C-state. + * ref: "Intel Processor Vendor-Specific ACPI Interface Specification" + */ + if ((c->x86_vendor == X86_VENDOR_INTEL) && !(reg->access_size & 0x2)) + cx->bm_sts_skip = 1; + return retval; } EXPORT_SYMBOL_GPL(acpi_processor_ffh_cstate_probe); 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); diff --git a/include/acpi/processor.h b/include/acpi/processor.h index da565a48240e..a68ca8a11a53 100644 --- a/include/acpi/processor.h +++ b/include/acpi/processor.h @@ -48,7 +48,7 @@ struct acpi_power_register { u8 space_id; u8 bit_width; u8 bit_offset; - u8 reserved; + u8 access_size; u64 address; } __attribute__ ((packed)); @@ -63,6 +63,7 @@ struct acpi_processor_cx { u32 power; u32 usage; u64 time; + u8 bm_sts_skip; char desc[ACPI_CX_DESC_LEN]; }; |