ACPI 2.0 / ECDT: Enable correct ECDT initialization order

With wrong ECDT fixes reverted, it is possible to put ECDT probing before
acpi_enable_subsystem().

But the ultimate purpose of ECDT re-enabling is to put the ECDT probing
before the namespace initialization (acpi_load_tables()). This patch
achieves this with protections so that we can enable it later when all
necessary corrections are upstreamed.

Link 4: https://bugzilla.kernel.org/show_bug.cgi?id=112911
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Tested-by: Chris Bainbridge <chris.bainbridge@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/bus.c

@@ -925,11 +925,13 @@ void __init acpi_early_init(void)
 		goto error0;
 	}
 
-	status = acpi_load_tables();
-	if (ACPI_FAILURE(status)) {
-		printk(KERN_ERR PREFIX
-		       "Unable to load the System Description Tables\n");
-		goto error0;
+	if (acpi_gbl_group_module_level_code) {
+		status = acpi_load_tables();
+		if (ACPI_FAILURE(status)) {
+			printk(KERN_ERR PREFIX
+			       "Unable to load the System Description Tables\n");
+			goto error0;
+		}
 	}
 
 #ifdef CONFIG_X86
@@ -995,17 +997,10 @@ static int __init acpi_bus_init(void)
 
 	acpi_os_initialize1();
 
-	status = acpi_enable_subsystem(ACPI_NO_ACPI_ENABLE);
-	if (ACPI_FAILURE(status)) {
-		printk(KERN_ERR PREFIX
-		       "Unable to start the ACPI Interpreter\n");
-		goto error1;
-	}
-
 	/*
 	 * ACPI 2.0 requires the EC driver to be loaded and work before
-	 * the EC device is found in the namespace (i.e. before acpi_initialize_objects()
-	 * is called).
+	 * the EC device is found in the namespace (i.e. before
+	 * acpi_load_tables() is called).
 	 *
 	 * This is accomplished by looking for the ECDT table, and getting
 	 * the EC parameters out of that.
@@ -1013,6 +1008,22 @@ static int __init acpi_bus_init(void)
 	status = acpi_ec_ecdt_probe();
 	/* Ignore result. Not having an ECDT is not fatal. */
 
+	if (!acpi_gbl_group_module_level_code) {
+		status = acpi_load_tables();
+		if (ACPI_FAILURE(status)) {
+			printk(KERN_ERR PREFIX
+			       "Unable to load the System Description Tables\n");
+			goto error1;
+		}
+	}
+
+	status = acpi_enable_subsystem(ACPI_NO_ACPI_ENABLE);
+	if (ACPI_FAILURE(status)) {
+		printk(KERN_ERR PREFIX
+		       "Unable to start the ACPI Interpreter\n");
+		goto error1;
+	}
+
 	status = acpi_initialize_objects(ACPI_FULL_INITIALIZATION);
 	if (ACPI_FAILURE(status)) {
 		printk(KERN_ERR PREFIX "Unable to initialize ACPI objects\n");