ACPI / EC: Fix regression related to PM ops support in ECDT device

On platforms (ASUS X550ZE and possibly all ASUS X series) with valid ECDT
EC but invalid DSDT EC, EC PM ops won't be invoked as ECDT EC is not an
ACPI device. Thus the following commit actually removed post-resume
acpi_ec_enable_event() invocation for such platforms, and triggered a
regression on them that after being resumed, EC (actually should be ECDT)
driver stops handling EC events:

Commit: c2b46d679b30c5c0d7eb47a21085943242bdd8dc
Subject: ACPI / EC: Add PM operations to improve event handling for resume process

Notice that the root cause actually is "ECDT is not an ACPI device" rather
than "the timing of acpi_ec_enable_event() invocation", this patch fixes
this issue by enumerating ECDT EC as an ACPI device. Due to the existence
of the noirq stage, the ability of tuning the timing of
acpi_ec_enable_event() invocation is still meaningful.

This patch is a little bit different from the posted fix by moving
acpi_config_boot_ec() from acpi_ec_ecdt_start() to acpi_ec_add() to make
sure that EC event handling won't be stopped as long as the ACPI EC driver
is bound. Thus the following sequence shouldn't disable EC event handling:
unbind,suspend,resume,bind.

Fixes: c2b46d679b30 (ACPI / EC: Add PM operations to improve event handling for resume process)
Link: https://bugzilla.kernel.org/show_bug.cgi?id=196847
Reported-by: Luya Tshimbalanga <[e-mail]>
Tested-by: Luya Tshimbalanga <[e-mail]>
Cc: 4.9+ <[e-mail]> # 4.9+
Signed-off-by: Lv Zheng <[e-mail]>
Signed-off-by: Rafael J. Wysocki <[e-mail]>

drivers/acpi/ec.c

···
 {
 	struct acpi_ec *ec = NULL;
 	int ret;
+	bool is_ecdt = false;
+	acpi_status status;
 
 	strcpy(acpi_device_name(device), ACPI_EC_DEVICE_NAME);
 	strcpy(acpi_device_class(device), ACPI_EC_CLASS);
 
-	ec = acpi_ec_alloc();
-	if (!ec)
-		return -ENOMEM;
-	if (ec_parse_device(device->handle, 0, ec, NULL) !=
-		AE_CTRL_TERMINATE) {
+	if (!strcmp(acpi_device_hid(device), ACPI_ECDT_HID)) {
+		is_ecdt = true;
+		ec = boot_ec;
+	} else {
+		ec = acpi_ec_alloc();
+		if (!ec)
+			return -ENOMEM;
+		status = ec_parse_device(device->handle, 0, ec, NULL);
+		if (status != AE_CTRL_TERMINATE) {
 			ret = -EINVAL;
 			goto err_alloc;
+		}
 	}
 
 	if (acpi_is_boot_ec(ec)) {
-		boot_ec_is_ecdt = false;
-		/*
-		 * Trust PNP0C09 namespace location rather than ECDT ID.
-		 *
-		 * But trust ECDT GPE rather than _GPE because of ASUS quirks,
-		 * so do not change boot_ec->gpe to ec->gpe.
-		 */
-		boot_ec->handle = ec->handle;
-		acpi_handle_debug(ec->handle, "duplicated.\n");
-		acpi_ec_free(ec);
-		ec = boot_ec;
-		ret = acpi_config_boot_ec(ec, ec->handle, true, false);
+		boot_ec_is_ecdt = is_ecdt;
+		if (!is_ecdt) {
+			/*
+			 * Trust PNP0C09 namespace location rather than
+			 * ECDT ID. But trust ECDT GPE rather than _GPE
+			 * because of ASUS quirks, so do not change
+			 * boot_ec->gpe to ec->gpe.
+			 */
+			boot_ec->handle = ec->handle;
+			acpi_handle_debug(ec->handle, "duplicated.\n");
+			acpi_ec_free(ec);
+			ec = boot_ec;
+		}
+		ret = acpi_config_boot_ec(ec, ec->handle, true, is_ecdt);
 	} else
 		ret = acpi_ec_setup(ec, true);
 	if (ret)
···
 	ret = !!request_region(ec->command_addr, 1, "EC cmd");
 	WARN(!ret, "Could not request EC cmd io port 0x%lx", ec->command_addr);
 
-	/* Reprobe devices depending on the EC */
-	acpi_walk_dep_device_list(ec->handle);
+	if (!is_ecdt) {
+		/* Reprobe devices depending on the EC */
+		acpi_walk_dep_device_list(ec->handle);
+	}
 	acpi_handle_debug(ec->handle, "enumerated.\n");
 	return 0;
 
···
 
 static const struct acpi_device_id ec_device_ids[] = {
 	{"PNP0C09", 0},
+	{ACPI_ECDT_HID, 0},
 	{"", 0},
 };
 
···
 	 * Note: ec->handle can be valid if this function is called after
 	 * acpi_ec_add(), hence the fast path.
 	 */
-	if (boot_ec->handle != ACPI_ROOT_OBJECT)
-		handle = boot_ec->handle;
-	else if (!acpi_ec_ecdt_get_handle(&handle))
-		return -ENODEV;
-	return acpi_config_boot_ec(boot_ec, handle, true, true);
+	if (boot_ec->handle == ACPI_ROOT_OBJECT) {
+		if (!acpi_ec_ecdt_get_handle(&handle))
+			return -ENODEV;
+		boot_ec->handle = handle;
+	}
+
+	/* Register to ACPI bus with PM ops attached */
+	return acpi_bus_register_early_device(ACPI_BUS_TYPE_ECDT_EC);
 }
 
 #if 0
···
 
 	/* Drivers must be started after acpi_ec_query_init() */
 	dsdt_fail = acpi_bus_register_driver(&acpi_ec_driver);
+	/*
+	 * Register ECDT to ACPI bus only when PNP0C09 probe fails. This is
+	 * useful for platforms (confirmed on ASUS X550ZE) with valid ECDT
+	 * settings but invalid DSDT settings.
+	 * https://bugzilla.kernel.org/show_bug.cgi?id=196847
+	 */
 	ecdt_fail = acpi_ec_ecdt_start();
 	return ecdt_fail && dsdt_fail ? -ENODEV : 0;
 }

drivers/acpi/internal.h

···
 bool acpi_device_is_battery(struct acpi_device *adev);
 bool acpi_device_is_first_physical_node(struct acpi_device *adev,
 					const struct device *dev);
+int acpi_bus_register_early_device(int type);
 
 /* --------------------------------------------------------------------------
                      Device Matching and Notification

drivers/acpi/scan.c

···
 	case ACPI_BUS_TYPE_SLEEP_BUTTON:
 		strcpy(device->pnp.bus_id, "SLPF");
 		break;
+	case ACPI_BUS_TYPE_ECDT_EC:
+		strcpy(device->pnp.bus_id, "ECDT");
+		break;
 	default:
 		acpi_get_name(device->handle, ACPI_SINGLE_NAME, &buffer);
 		/* Clean up trailing underscores (if any) */
···
 		break;
 	case ACPI_BUS_TYPE_SLEEP_BUTTON:
 		acpi_add_id(pnp, ACPI_BUTTON_HID_SLEEPF);
+		break;
+	case ACPI_BUS_TYPE_ECDT_EC:
+		acpi_add_id(pnp, ACPI_ECDT_HID);
 		break;
 	}
 }
···
 	acpi_device_clear_enumerated(adev);
 }
 EXPORT_SYMBOL_GPL(acpi_bus_trim);
+
+int acpi_bus_register_early_device(int type)
+{
+	struct acpi_device *device = NULL;
+	int result;
+
+	result = acpi_add_single_object(&device, NULL,
+					type, ACPI_STA_DEFAULT);
+	if (result)
+		return result;
+
+	device->flags.match_driver = true;
+	return device_attach(&device->dev);
+}
+EXPORT_SYMBOL_GPL(acpi_bus_register_early_device);
 
 static int acpi_bus_scan_fixed(void)
 {

include/acpi/acpi_bus.h

···
 	ACPI_BUS_TYPE_THERMAL,
 	ACPI_BUS_TYPE_POWER_BUTTON,
 	ACPI_BUS_TYPE_SLEEP_BUTTON,
+	ACPI_BUS_TYPE_ECDT_EC,
 	ACPI_BUS_DEVICE_TYPE_COUNT
 };
 

include/acpi/acpi_drivers.h

···
 #define ACPI_VIDEO_HID			"LNXVIDEO"
 #define ACPI_BAY_HID			"LNXIOBAY"
 #define ACPI_DOCK_HID			"LNXDOCK"
+#define ACPI_ECDT_HID			"LNXEC"
 /* Quirk for broken IBM BIOSes */
 #define ACPI_SMBUS_IBM_HID		"SMBUSIBM"