Add reset watchdogHEADmaster

Although CS has been pretty reliable for me, I recently experienced
a lockup in the middle of a remote debugging session. And I really
mean *very* remote, without a living (or dead) soul able to pull
the plug on the damn thing.

So while I know there is an annoying bug hiding somewhere, I also
think the device should be able to get back to a sane state on its
own.

So let's add a watchdog and a timer. The timer kicks the watchdog
every second, and the watchdog will reset the pico after 5s without
kicking. To test the feature, there is a "^\" command available
in debug mode that will crash the CS, leading to a reset after 5s.

The default conserver configuration is to reconnect after a minute,
which seems to be good enough for my use cases. Other console SW
probably have something similar.

Signed-off-by: Marc Zyngier <maz@kernel.org>

2 files changed, 30 insertions, 3 deletions

diff --git a/README b/README
index eed6794..d4b7b00 100644
--- a/README
+++ b/README
@@ -241,12 +241,15 @@ which is completely self explainatory, but let's expand on it anyway:
   That's a debug feature...
 
 - ^_ 1  Configure the Mac's serial on Primary USB pins. On v3+, this
-  also isolates the micro-USb connector. On older versions, it
+  also isolates the micro-USB connector. On older versions, it
   doesn't, so make sure you don't have anything plugged there.
 
 - ^_ 2 Configure the Mac's serial on SBU pins, which is the default.
   On v3+, this enables the use of the micro-USB connector.
 
+- ^_ ^\ crashes the Central Scrutinizer when in debug mode. This
+  allows testing the watchdog reset functionnality.
+
 - ^_ ? prints the help message (duh).
 
 Finally, the Port 0:/1: lines indicate which I2C/UART combinations the
diff --git a/vdmtool.c b/vdmtool.c
index 209c0f7..556116d 100644
--- a/vdmtool.c
+++ b/vdmtool.c
@@ -446,9 +446,11 @@ static void help(struct vdm_context *cxt)
 		"^_ 2  Serial on SBU pins\n");
 
 	if (upstream_is_serial())
-		cprintf_cont(cxt, "^_ ^@  Send break\n");
+		cprintf_cont(cxt, "^_ ^@ Send break\n");
 	if (PORT(cxt) == 0 && !vdm_contexts[1].hw)
-		cprintf_cont(cxt, "^_ ^U  Switch upstream port USB/Serial\n");
+		cprintf_cont(cxt, "^_ ^U Switch upstream port USB/Serial\n");
+	if (cxt->verbose)
+		cprintf_cont(cxt, "^_ ^\\ Crash me now\n");
 	cprintf_cont(cxt, "^_ ?  This message\n");
 
 	for (int i = 0; i < CONFIG_USB_PD_PORT_COUNT; i++) {
@@ -550,6 +552,12 @@ static bool serial_handler(struct vdm_context *cxt)
 			cxt->pending = true;
 			evt_disconnect(cxt);
 			break;
+		case 0x1c:			/* ^\ */
+			if (cxt->verbose) {
+				void (*crashme)(void) = NULL - 1;
+				crashme();
+			}
+			break;
 		case '?':
 			help(cxt);
 			break;
@@ -716,6 +724,18 @@ static bool m1_pd_bmc_run_one(struct vdm_context *cxt)
 	return serial_handler(cxt) || cxt->pending;
 }
 
+/* A tick every second, watchdog fires after 5s */
+#define WDT_PERIOD_MS		(5 * 1000)
+#define TICK_PERIOD_MS		(1 * 1000)
+#define TICK_PERIOD_US		(TICK_PERIOD_MS * 1000)
+
+static int64_t tick_cb(alarm_id_t id, void *arg)
+{
+	watchdog_update();
+
+	return TICK_PERIOD_US;
+}
+
 #define for_each_cxt(___c)						\
 	for (struct vdm_context *___c = &vdm_contexts[0];		\
 	     (___c - vdm_contexts) < CONFIG_USB_PD_PORT_COUNT;		\
@@ -724,6 +744,10 @@ static bool m1_pd_bmc_run_one(struct vdm_context *cxt)
 
 void m1_pd_bmc_run(void)
 {
+	watchdog_enable(WDT_PERIOD_MS, 1);
+
+	add_alarm_in_ms(TICK_PERIOD_MS, tick_cb, NULL, true);
+
 	while (1) {
 		bool busy = false;