avr: Implement reset command

Support restarting the mcu using the watchdog feature of AVR chips via
a new reset command.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

1 files changed, 22 insertions, 2 deletions

diff --git a/src/avr/watchdog.c b/src/avr/watchdog.c
index f925a8d5..306f2cd8 100644
--- a/src/avr/watchdog.c
+++ b/src/avr/watchdog.c
@@ -7,6 +7,7 @@
 #include <avr/interrupt.h> // WDT_vect
 #include <avr/wdt.h> // wdt_enable
 #include "command.h" // shutdown
+#include "irq.h" // irq_disable
 #include "sched.h" // DECL_TASK
 
 static uint8_t watchdog_shutdown;
@@ -22,7 +23,7 @@ watchdog_reset(void)
 {
     wdt_reset();
     if (watchdog_shutdown) {
-        WDTCSR |= 1<<WDIE;
+        WDTCSR = 1<<WDIE;
         watchdog_shutdown = 0;
     }
 }
@@ -33,6 +34,25 @@ watchdog_init(void)
 {
     // 0.5s timeout, interrupt and system reset
     wdt_enable(WDTO_500MS);
-    WDTCSR |= 1<<WDIE;
+    WDTCSR = 1<<WDIE;
 }
 DECL_INIT(watchdog_init);
+
+// Very early reset of the watchdog
+void __attribute__((naked)) __visible __section(".init3")
+watchdog_early_init(void)
+{
+    MCUSR = 0;
+    wdt_disable();
+}
+
+// Support reset on AVR via the watchdog timer
+void
+command_reset(uint32_t *args)
+{
+    irq_disable();
+    wdt_enable(WDTO_15MS);
+    for (;;)
+        ;
+}
+DECL_COMMAND_FLAGS(command_reset, HF_IN_SHUTDOWN, "reset");