From a7b699b27e07460a852bc4202311bd278053dffb Mon Sep 17 00:00:00 2001
From: Yann GASCUEL <34003959+lnv42@users.noreply.github.com>
Date: Fri, 10 Feb 2023 13:24:58 +0100
Subject: [PATCH] fix infinity loop in SpinDelayUs() and SpinDelayUsPrecision()

I don't know why : but AT91C_BASE_PWMC_CH0->PWMC_CCNTR value is never
equal to 0, so if start+ticks was equal to 0, it was inifity looping.
This fix may produce bit longer wait than expected in some case,
depending on if AT91C_BASE_PWMC_CH0->PWMC_CCNTR delay between 0xFFFF
and 0x0001 is just 1 step or 2...

/!\ Figure out why AT91C_BASE_PWMC_CH0->PWMC_CCNTR is never 0 and fix
it there is probably a better way to fix this infinity loop issue /!\
---
 armsrc/ticks.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/armsrc/ticks.c b/armsrc/ticks.c
index 61089595c..3cf2c54dc 100644
--- a/armsrc/ticks.c
+++ b/armsrc/ticks.c
@@ -35,11 +35,14 @@ void SpinDelayUsPrecision(int us) {
     AT91C_BASE_PWMC_CH0->PWMC_CDTYR = 0;                           // Channel Duty Cycle Register
     AT91C_BASE_PWMC_CH0->PWMC_CPRDR = 0xFFFF;                      // Channel Period Register
 
-    uint16_t start = AT91C_BASE_PWMC_CH0->PWMC_CCNTR;
+    uint16_t end = AT91C_BASE_PWMC_CH0->PWMC_CCNTR + ticks;
+    if (end == 0) // AT91C_BASE_PWMC_CH0->PWMC_CCNTR is never == 0
+        end++;    // so we have to end++ to avoid inivity loop
 
     for (;;) {
         uint16_t now = AT91C_BASE_PWMC_CH0->PWMC_CCNTR;
-        if (now == (uint16_t)(start + ticks))
+
+        if (now == end)
             return;
 
         WDT_HIT();
@@ -59,13 +62,15 @@ void SpinDelayUs(int us) {
     AT91C_BASE_PWMC_CH0->PWMC_CDTYR = 0;                            // Channel Duty Cycle Register
     AT91C_BASE_PWMC_CH0->PWMC_CPRDR = 0xffff;                       // Channel Period Register
 
-    uint16_t start = AT91C_BASE_PWMC_CH0->PWMC_CCNTR;
+    uint16_t end = AT91C_BASE_PWMC_CH0->PWMC_CCNTR + ticks;
+    if (end == 0) // AT91C_BASE_PWMC_CH0->PWMC_CCNTR is never == 0
+        end++;    // so we have to end++ to avoid inivity loop
 
     for (;;) {
         uint16_t now = AT91C_BASE_PWMC_CH0->PWMC_CCNTR;
-        if (now == (uint16_t)(start + ticks))
-            return;
 
+        if (now == end)
+            return;
         WDT_HIT();
     }
 }