greybus: gpio: Add runtime_pm suppourt

Add runtime pm support for the gpio driver.
Since there is no remote wakeup support, the
module will not suspend as long as a gpio is
requested.

Maybe an optimization could be made, to allow suspend
if all the requested gpios are in output mode, since
the bridge should maintain the state of the gpio
during suspend.

Testing Done: using the test board, let the
gpbrige enter standby and request a gpio.

Signed-off-by: Axel Haslam <[e-mail]>
Signed-off-by: David Lin <[e-mail]>
Reviewed-by: Johan Hovold <[e-mail]>
Signed-off-by: Alex Elder <[e-mail]>

drivers/staging/greybus/gpio.c

···
 static int gb_gpio_activate_operation(struct gb_gpio_controller *ggc, u8 which)
 {
 	struct gb_gpio_activate_request request;
+	struct gbphy_device *gbphy_dev = ggc->gbphy_dev;
 	int ret;
+
+	ret = gbphy_runtime_get_sync(gbphy_dev);
+	if (ret)
+		return ret;
 
 	request.which = which;
 	ret = gb_operation_sync(ggc->connection, GB_GPIO_TYPE_ACTIVATE,
 				 &request, sizeof(request), NULL, 0);
-	if (!ret)
-		ggc->lines[which].active = true;
-	return ret;
+	if (ret) {
+		gbphy_runtime_put_autosuspend(gbphy_dev);
+		return ret;
+	}
+
+	ggc->lines[which].active = true;
+
+	return 0;
 }
 
 static void gb_gpio_deactivate_operation(struct gb_gpio_controller *ggc,
 					u8 which)
 {
-	struct device *dev = &ggc->gbphy_dev->dev;
+	struct gbphy_device *gbphy_dev = ggc->gbphy_dev;
+	struct device *dev = &gbphy_dev->dev;
 	struct gb_gpio_deactivate_request request;
 	int ret;
 
···
 				 &request, sizeof(request), NULL, 0);
 	if (ret) {
 		dev_err(dev, "failed to deactivate gpio %u\n", which);
-		return;
+		goto out_pm_put;
 	}
 
 	ggc->lines[which].active = false;
+
+out_pm_put:
+	gbphy_runtime_put_autosuspend(gbphy_dev);
 }
 
 static int gb_gpio_get_direction_operation(struct gb_gpio_controller *ggc,
···
 		goto exit_gpiochip_remove;
 	}
 
+	gbphy_runtime_put_autosuspend(gbphy_dev);
 	return 0;
 
 exit_gpiochip_remove:
···
 {
 	struct gb_gpio_controller *ggc = gb_gbphy_get_data(gbphy_dev);
 	struct gb_connection *connection = ggc->connection;
+	int ret;
+
+	ret = gbphy_runtime_get_sync(gbphy_dev);
+	if (ret)
+		gbphy_runtime_get_noresume(gbphy_dev);
 
 	gb_connection_disable_rx(connection);
 	gb_gpio_irqchip_remove(ggc);