ACPI: EC: Consolidate event handler installation code

Commit 406857f7 ("ACPI: EC: add support for hardware-reduced
systems") made ec_install_handlers() return an error on failures
to configure a GPIO IRQ for the EC, but that is inconsistent with
the handling of the GPE event handler installation failures even
though it is exactly the same issue and the driver can respond to
it in the same way in both cases (the EC can be actively polled
for events through its registers if the event handler installation
fails).

Moreover, it requires acpi_ec_add() to take that special case into
account and disagrees with the ec_install_handlers() header comment.

For this reason, rework the event handler installation code in
ec_install_handlers() to explicitly take deferred probing (that
may be needed in the GPIO IRQ case) into account and to avoid
failing the EC initialization in any other case.

Among other things, reduce code duplication between
install_gpe_event_handler() and install_gpio_irq_event_handler() by
moving some code from there into ec_install_handlers() itself and
simplify the error code path in acpi_ec_add().

While at it, turn the ec_install_handlers() header comment into
a proper kerneldoc one and add some general control flow information
to it.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Jian-Hong Pan <jian-hong@endlessm.com>

drivers/acpi/ec.c

@@ -1427,54 +1427,43 @@ ec_parse_device(acpi_handle handle, u32 Level, void *context, void **retval)
 	return AE_CTRL_TERMINATE;
 }
 
-static void install_gpe_event_handler(struct acpi_ec *ec)
-{
-	acpi_status status =
-		acpi_install_gpe_raw_handler(NULL, ec->gpe,
-					     ACPI_GPE_EDGE_TRIGGERED,
-					     &acpi_ec_gpe_handler,
-					     ec);
-	if (ACPI_SUCCESS(status)) {
-		/* This is not fatal as we can poll EC events */
-		set_bit(EC_FLAGS_EVENT_HANDLER_INSTALLED, &ec->flags);
-		acpi_ec_leave_noirq(ec);
-		if (test_bit(EC_FLAGS_STARTED, &ec->flags) &&
-		    ec->reference_count >= 1)
-			acpi_ec_enable_gpe(ec, true);
-	}
-}
-
-/* ACPI reduced hardware platforms use a GpioInt specified in _CRS. */
-static int install_gpio_irq_event_handler(struct acpi_ec *ec,
-					  struct acpi_device *device)
+static bool install_gpe_event_handler(struct acpi_ec *ec)
 {
-	int irq = acpi_dev_gpio_irq_get(device, 0);
-	int ret;
-
-	if (irq < 0)
-		return irq;
+	acpi_status status;
 
-	ret = request_irq(irq, acpi_ec_irq_handler, IRQF_SHARED,
-			  "ACPI EC", ec);
+	status = acpi_install_gpe_raw_handler(NULL, ec->gpe,
+					      ACPI_GPE_EDGE_TRIGGERED,
+					      &acpi_ec_gpe_handler, ec);
+	if (ACPI_FAILURE(status))
+		return false;
 
-	/*
-	 * Unlike the GPE case, we treat errors here as fatal, we'll only
-	 * implement GPIO polling if we find a case that needs it.
-	 */
-	if (ret < 0)
-		return ret;
+	if (test_bit(EC_FLAGS_STARTED, &ec->flags) && ec->reference_count >= 1)
+		acpi_ec_enable_gpe(ec, true);
 
-	ec->irq = irq;
-	set_bit(EC_FLAGS_EVENT_HANDLER_INSTALLED, &ec->flags);
-	acpi_ec_leave_noirq(ec);
+	return true;
+}
 
-	return 0;
+static bool install_gpio_irq_event_handler(struct acpi_ec *ec)
+{
+	return request_irq(ec->irq, acpi_ec_irq_handler, IRQF_SHARED,
+			   "ACPI EC", ec) >= 0;
 }
 
-/*
- * Note: This function returns an error code only when the address space
- *       handler is not installed, which means "not able to handle
- *       transactions".
+/**
+ * ec_install_handlers - Install service callbacks and register query methods.
+ * @ec: Target EC.
+ * @device: ACPI device object corresponding to @ec.
+ *
+ * Install a handler for the EC address space type unless it has been installed
+ * already.  If @device is not NULL, also look for EC query methods in the
+ * namespace and register them, and install an event (either GPE or GPIO IRQ)
+ * handler for the EC, if possible.
+ *
+ * Return:
+ * -ENODEV if the address space handler cannot be installed, which means
+ *  "unable to handle transactions",
+ * -EPROBE_DEFER if GPIO IRQ acquisition needs to be deferred,
+ * or 0 (success) otherwise.
  */
 static int ec_install_handlers(struct acpi_ec *ec, struct acpi_device *device)
 {
@@ -1498,6 +1487,19 @@ static int ec_install_handlers(struct acpi_ec *ec, struct acpi_device *device)
 	if (!device)
 		return 0;
 
+	if (ec->gpe < 0) {
+		/* ACPI reduced hardware platforms use a GpioInt from _CRS. */
+		int irq = acpi_dev_gpio_irq_get(device, 0);
+		/*
+		 * Bail out right away for deferred probing or complete the
+		 * initialization regardless of any other errors.
+		 */
+		if (irq == -EPROBE_DEFER)
+			return -EPROBE_DEFER;
+		else if (irq >= 0)
+			ec->irq = irq;
+	}
+
 	if (!test_bit(EC_FLAGS_QUERY_METHODS_INSTALLED, &ec->flags)) {
 		/* Find and register all query methods */
 		acpi_walk_namespace(ACPI_TYPE_METHOD, ec->handle, 1,
@@ -1506,13 +1508,21 @@ static int ec_install_handlers(struct acpi_ec *ec, struct acpi_device *device)
 		set_bit(EC_FLAGS_QUERY_METHODS_INSTALLED, &ec->flags);
 	}
 	if (!test_bit(EC_FLAGS_EVENT_HANDLER_INSTALLED, &ec->flags)) {
-		if (ec->gpe >= 0) {
-			install_gpe_event_handler(ec);
-		} else {
-			int ret = install_gpio_irq_event_handler(ec, device);
-			if (ret)
-				return ret;
+		bool ready = false;
+
+		if (ec->gpe >= 0)
+			ready = install_gpe_event_handler(ec);
+		else if (ec->irq >= 0)
+			ready = install_gpio_irq_event_handler(ec);
+
+		if (ready) {
+			set_bit(EC_FLAGS_EVENT_HANDLER_INSTALLED, &ec->flags);
+			acpi_ec_leave_noirq(ec);
 		}
+		/*
+		 * Failures to install an event handler are not fatal, because
+		 * the EC can be polled for events.
+		 */
 	}
 	/* EC is fully operational, allow queries */
 	acpi_ec_enable_event(ec);
@@ -1625,7 +1635,7 @@ static int acpi_ec_add(struct acpi_device *device)
 		status = ec_parse_device(device->handle, 0, ec, NULL);
 		if (status != AE_CTRL_TERMINATE) {
 			ret = -EINVAL;
-			goto err_alloc;
+			goto err;
 		}
 
 		if (boot_ec && ec->command_addr == boot_ec->command_addr &&
@@ -1646,7 +1656,7 @@ static int acpi_ec_add(struct acpi_device *device)
 
 	ret = acpi_ec_setup(ec, device);
 	if (ret)
-		goto err_query;
+		goto err;
 
 	if (ec == boot_ec)
 		acpi_handle_info(boot_ec->handle,
@@ -1666,12 +1676,10 @@ static int acpi_ec_add(struct acpi_device *device)
 	acpi_handle_debug(ec->handle, "enumerated.\n");
 	return 0;
 
-err_query:
-	if (ec != boot_ec)
-		acpi_ec_remove_query_handlers(ec, true, 0);
-err_alloc:
+err:
 	if (ec != boot_ec)
 		acpi_ec_free(ec);
+
 	return ret;
 }