ACPICA: Update for ACPI 5 hardware-reduced feature

Ensure that AcpiEnable and AcpiDisable work properly when the
hardware-reduced flag is set in the FADT.

Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/acpica/evxfevnt.c

@@ -74,6 +74,12 @@ acpi_status acpi_enable(void)
 		return_ACPI_STATUS(AE_NO_ACPI_TABLES);
 	}
 
+	/* If the Hardware Reduced flag is set, machine is always in acpi mode */
+
+	if (acpi_gbl_reduced_hardware) {
+		return_ACPI_STATUS(AE_OK);
+	}
+
 	/* Check current mode */
 
 	if (acpi_hw_get_mode() == ACPI_SYS_MODE_ACPI) {
@@ -126,6 +132,12 @@ acpi_status acpi_disable(void)
 
 	ACPI_FUNCTION_TRACE(acpi_disable);
 
+	/* If the Hardware Reduced flag is set, machine is always in acpi mode */
+
+	if (acpi_gbl_reduced_hardware) {
+		return_ACPI_STATUS(AE_OK);
+	}
+
 	if (acpi_hw_get_mode() == ACPI_SYS_MODE_LEGACY) {
 		ACPI_DEBUG_PRINT((ACPI_DB_INIT,
 				  "System is already in legacy (non-ACPI) mode\n"));

drivers/acpi/acpica/hwacpi.c

@@ -66,6 +66,12 @@ acpi_status acpi_hw_set_mode(u32 mode)
 
 	ACPI_FUNCTION_TRACE(hw_set_mode);
 
+	/* If the Hardware Reduced flag is set, machine is always in acpi mode */
+
+	if (acpi_gbl_reduced_hardware) {
+		return_ACPI_STATUS(AE_OK);
+	}
+
 	/*
 	 * ACPI 2.0 clarified that if SMI_CMD in FADT is zero,
 	 * system does not support mode transition.
@@ -146,6 +152,12 @@ u32 acpi_hw_get_mode(void)
 
 	ACPI_FUNCTION_TRACE(hw_get_mode);
 
+	/* If the Hardware Reduced flag is set, machine is always in acpi mode */
+
+	if (acpi_gbl_reduced_hardware) {
+		return_VALUE(ACPI_SYS_MODE_ACPI);
+	}
+
 	/*
 	 * ACPI 2.0 clarified that if SMI_CMD in FADT is zero,
 	 * system does not support mode transition.