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authorLen Brown <len.brown@intel.com>2010-07-22 16:54:27 -0400
committerGreg Kroah-Hartman <gregkh@suse.de>2010-08-02 10:21:24 -0700
commit447cc37695575ab9fa8b00427b00ca228832ec25 (patch)
treeb802fe31ba5dae24eec039e1cdf6cf1bd27d3241
parent784724e6862571cde726a78287d16867fbbf2b28 (diff)
ACPI: skip checking BM_STS if the BIOS doesn't ask for it
commit 718be4aaf3613cf7c2d097f925abc3d3553c0605 upstream. 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> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--arch/x86/kernel/acpi/cstate.c9
-rw-r--r--drivers/acpi/processor_idle.c2
-rw-r--r--include/acpi/processor.h3
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 c8f0797416a5..a6ad608c96a2 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -962,7 +962,7 @@ 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 740ac3ad8fd0..e7bdaafabc3f 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));
@@ -74,6 +74,7 @@ struct acpi_processor_cx {
u32 power;
u32 usage;
u64 time;
+ u8 bm_sts_skip;
struct acpi_processor_cx_policy promotion;
struct acpi_processor_cx_policy demotion;
char desc[ACPI_CX_DESC_LEN];