From a078b091c1690f0f6298d771aea042c7fe7288df Mon Sep 17 00:00:00 2001
From: Sebastian Huber <sebastian.huber@embedded-brains.de>
Date: Fri, 30 Aug 2024 09:29:00 +0200
Subject: [PATCH] dev/serial: Use _IO_Relax()

This reduces the system bus load while waiting for a state change.  In
addition, it simplifies testing by using a wrapped _IO_Relax().
---
 bsps/shared/dev/serial/zynq-uart-polled.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/bsps/shared/dev/serial/zynq-uart-polled.c b/bsps/shared/dev/serial/zynq-uart-polled.c
index dbd61cb79b..17c80af104 100644
--- a/bsps/shared/dev/serial/zynq-uart-polled.c
+++ b/bsps/shared/dev/serial/zynq-uart-polled.c
@@ -34,11 +34,12 @@
  * POSSIBILITY OF SUCH DAMAGE.
  */
 
-#include <dev/serial/zynq-uart.h>
 #include <dev/serial/zynq-uart-regs.h>
 
 #include <bspopts.h>
 
+#include <rtems/dev/io.h>
+
 /*
  * Make weak and let the user override.
  */
@@ -165,7 +166,7 @@ int zynq_uart_read_char_polled(volatile zynq_uart *regs)
 void zynq_uart_write_char_polled(volatile zynq_uart *regs, char c)
 {
   while ((regs->channel_sts & ZYNQ_UART_CHANNEL_STS_TNFUL) != 0) {
-    /* Wait */
+    _IO_Relax();
   }
 
   regs->tx_rx_fifo = ZYNQ_UART_TX_RX_FIFO_FIFO(c);