drivers: uart: silabs: revert pm deletion for usart_gecko

Revert delete of the uart_gecko_pm_action function.

Signed-off-by: Martin Hoff <[email protected]>

Author: Martinhoff-maker

drivers/serial/uart_gecko.c

@@ -669,6 +669,31 @@ static int uart_gecko_init(const struct device *dev)
 	return 0;
 }
 
+#ifdef CONFIG_PM_DEVICE
+static int uart_gecko_pm_action(const struct device *dev, enum pm_device_action action)
+{
+	__maybe_unused const struct uart_gecko_config *config = dev->config;
+
+	switch (action) {
+	case PM_DEVICE_ACTION_SUSPEND:
+#ifdef USART_STATUS_TXIDLE
+		/* Wait for TX FIFO to flush before suspending */
+		while (!(USART_StatusGet(config->base) & USART_STATUS_TXIDLE)) {
+		}
+#endif
+		break;
+
+	case PM_DEVICE_ACTION_RESUME:
+		break;
+
+	default:
+		return -ENOTSUP;
+	}
+
+	return 0;
+}
+#endif
+
 static DEVICE_API(uart, uart_gecko_driver_api) = {
 	.poll_in = uart_gecko_poll_in,
 	.poll_out = uart_gecko_poll_out,