From 9b3a80cc372a4942f19e6f328f141c3712eddb1c Mon Sep 17 00:00:00 2001
From: SPRESENSE <41312067+SPRESENSE@users.noreply.github.com>
Date: Wed, 19 May 2021 17:03:36 +0900
Subject: [PATCH] arch: cxd56xx: Fix uart getting stuck during a clock change

UART driver is stopped and re-started during a clock change. When a UART
interrupt is generated in each process, the unexpected behavior will
occur and a console will get stuck with UART driver. This commit fixed
each process is performed atomically.
---
 arch/arm/src/cxd56xx/cxd56_uart.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/arm/src/cxd56xx/cxd56_uart.c b/arch/arm/src/cxd56xx/cxd56_uart.c
index b8b2f3caeb..3ddfac640e 100644
--- a/arch/arm/src/cxd56xx/cxd56_uart.c
+++ b/arch/arm/src/cxd56xx/cxd56_uart.c
@@ -206,11 +206,15 @@ static void cxd56_uart_pincontrol(int ch, bool on)
 
 static void cxd56_uart_start(int ch)
 {
+  irqstate_t flags = enter_critical_section();
+
   cxd56_setbaud(CONSOLE_BASE, CONSOLE_BASEFREQ, CONSOLE_BAUD);
 
   putreg32(g_lcr, g_uartdevs[ch].uartbase + CXD56_UART_LCR_H);
 
   putreg32(g_cr, g_uartdevs[ch].uartbase + CXD56_UART_CR);
+
+  leave_critical_section(flags);
 }
 
 /****************************************************************************
@@ -226,6 +230,8 @@ static void cxd56_uart_stop(int ch)
 {
   uint32_t cr;
 
+  irqstate_t flags = enter_critical_section();
+
   while (UART_FR_BUSY & getreg32(g_uartdevs[ch].uartbase + CXD56_UART_FR));
 
   cr   = getreg32(g_uartdevs[ch].uartbase + CXD56_UART_CR);
@@ -235,6 +241,8 @@ static void cxd56_uart_stop(int ch)
 
   g_lcr = getreg32(g_uartdevs[ch].uartbase + CXD56_UART_LCR_H);
   putreg32(0, g_uartdevs[ch].uartbase + CXD56_UART_LCR_H);
+
+  leave_critical_section(flags);
 }
 
 /****************************************************************************