From 8f348778e12d3c8a55c6fe4c4475bb9ab07aa978 Mon Sep 17 00:00:00 2001
From: Damien George <damien.p.george@gmail.com>
Date: Fri, 15 May 2020 00:44:25 +1000
Subject: [PATCH] nrf/mphalport: Remove need for "syntax unified" in
 mp_hal_delay_us.

Because it can confuse older versions of gcc.  Instead use the correct
instruction for Thumb vs Thumb-2 (sub vs subs) so the assembler emits the
2-byte instruction.

Related to commit 1aa9ff914194824a78a8b010572ad7083c1bb4ec.
---
 ports/nrf/mphalport.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/ports/nrf/mphalport.c b/ports/nrf/mphalport.c
index bdedea9d01..4469adc80d 100644
--- a/ports/nrf/mphalport.c
+++ b/ports/nrf/mphalport.c
@@ -99,11 +99,12 @@ void mp_hal_delay_us(mp_uint_t us) {
     }
     register uint32_t delay __ASM("r0") = us;
     __ASM volatile (
-        #ifdef NRF51
-        ".syntax unified\n"
-        #endif
         "1:\n"
+        #ifdef NRF51
+        " SUB %0, %0, #1\n"
+        #else
         " SUBS %0, %0, #1\n"
+        #endif
         " NOP\n"
         " NOP\n"
         " NOP\n"