Wipe config if button held at boot

Blocking by design to prevent loading config

Button must be held between 10 and 30 seconds to trigger reset.

If held more than 30 seconds, boot normally. This is to prevent lock-up in case of weird hardware variants.

rtlplayground.c

@@ -30,6 +30,8 @@ extern __xdata uint32_t flash_size;
 extern __xdata uint16_t crc_value;
 __xdata struct machine_runtime machine_detected;
 void crc16(__xdata uint8_t *v) __naked;
+void flash_default_config(void);
+void early_boot_handle_button(void);
 
 // See setup_serial_timer1() for valid baudrate settings!
 #define SERIAL_BAUD_RATE 115200
@@ -734,6 +736,44 @@ void delay(uint16_t t)
 		PCON |= 1;
 }
 
+void early_boot_handle_button(void)
+{
+	if (machine.reset_pin == GPIO_NA)
+		return;
+
+	gpio_input_setup(machine.reset_pin);
+
+	// Debounce after init
+	delay(100);
+	// If the button is not already held at boot, continue normally.
+	if (gpio_pin_test(machine.reset_pin))
+		return;
+
+	print_string("\n[Reset button held at boot]\n");
+
+	if (gpio_pin_test(machine.reset_pin))
+		return;
+
+	const __xdata uint32_t min_hold_ticks = 10UL * SYS_TICK_HZ;
+	const __xdata uint32_t max_hold_ticks = 30UL * SYS_TICK_HZ;
+	__xdata uint32_t start_ticks = ticks;
+
+	while (!gpio_pin_test(machine.reset_pin)) {
+		__xdata uint32_t held_ticks = ticks - start_ticks;
+
+		if (held_ticks > max_hold_ticks) {
+			print_string("[Button held >30s at boot; continuing normal boot]\n");
+			return;
+		}
+
+		PCON |= 1;
+	}
+
+	if ((ticks - start_ticks) >= min_hold_ticks) {
+		print_string("[Button held 10s-30s at boot; restoring default config]\n");
+		flash_default_config();
+	}
+}
 
 /*
  * Configure the SerDes of the SoC for a particular mode
@@ -2133,6 +2173,8 @@ void main(void)
 //	p031f.a610:2058 p041f.a610:2058  p051f.a610:2058  r4f3c:00000000 p061f.a610:2058 p071f.a610:2058 
 	port_stats_print();
 
+	early_boot_handle_button();
+
 	execute_config();
 	print_string("\n> ");
 	idle_ready = 1;