From 24ec55baa79ce6b76f65ef2dab8eee85e0dc703e Mon Sep 17 00:00:00 2001
From: Stefan Kerkmann <karlk90@pm.me>
Date: Sat, 3 Jul 2021 13:50:03 +0200
Subject: [PATCH] Free B4 pin on Longan Nano Board

By default B4 has the JTAG NJRST signal with a pull up enabled. On the longan Nano
this PIN is broken out as a regular pin. So we just disable NJRST by default
and make it available as a regular GPIO.
---
 os/hal/boards/SIPEED_LONGAN_NANO/board.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/os/hal/boards/SIPEED_LONGAN_NANO/board.c b/os/hal/boards/SIPEED_LONGAN_NANO/board.c
index 6bf05ce0..36a27cb5 100644
--- a/os/hal/boards/SIPEED_LONGAN_NANO/board.c
+++ b/os/hal/boards/SIPEED_LONGAN_NANO/board.c
@@ -44,4 +44,6 @@ void __early_init(void) {
  * Board-specific initialization code.
  */
 void boardInit(void) {
+    /* Free B4 pin by disabling JTAG NJTRST. */
+    AFIO->PCF0 |= AFIO_PCF0_SWJ_CFG_NOJNTRST;
 }