Merge branch 'bugzilla-15886' into release

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);

drivers/acpi/processor_idle.c

@@ -76,6 +76,8 @@ static unsigned int max_cstate __read_mostly = ACPI_PROCESSOR_MAX_POWER;
 module_param(max_cstate, uint, 0000);
 static unsigned int nocst __read_mostly;
 module_param(nocst, uint, 0000);
+static int bm_check_disable __read_mostly;
+module_param(bm_check_disable, uint, 0000);
 
 static unsigned int latency_factor __read_mostly = 2;
 module_param(latency_factor, uint, 0644);
@@ -763,6 +765,9 @@ static int acpi_idle_bm_check(void)
 {
 	u32 bm_status = 0;
 
+	if (bm_check_disable)
+		return 0;
+
 	acpi_read_bit_register(ACPI_BITREG_BUS_MASTER_STATUS, &bm_status);
 	if (bm_status)
 		acpi_write_bit_register(ACPI_BITREG_BUS_MASTER_STATUS, 1);
@@ -947,7 +952,7 @@ 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);

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];
 };