Add debug helpers that communicate information via the LED.

Blink patterns and delay mechanisms allow for "easier" debugging using
just the onboard LED on the raspberry pi.

headers/private/kernel/boot/platform/raspberrypi_arm/platform_debug.h

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2012, Haiku Inc. All rights reserved.
+ * Distributed under the terms of the MIT License.
+ */
+#ifndef _PLATFORM_DEBUG_H_
+#define _PLATFORM_DEBUG_H_
+
+#define DEBUG_DELAY_SHORT		200
+#define DEBUG_DELAY_MEDIUM		500
+#define DEBUG_DELAY_LONG		1000
+
+void debug_delay(int time);
+void debug_set_led(bool on);
+
+void debug_toggle_led(int count, int delay = DEBUG_DELAY_MEDIUM);
+	// Toggles the led count times with the delay for both on and off time.
+
+void debug_blink_number(int number);
+	// Implements a blink pattern to output arbitrary numbers:
+	//
+	//	1.	Led turns off and stays off for a long delay.
+	//	2.	Led blinks x times with a short delay, where x is the current
+	//		decimal place + 1 (so 0 values are easier to see).
+	//	3.	Led stays off for a long delay to indicate the move to the next
+	//		decimal place and step 2. is repeated until all the rest of the
+	//		number is 0.
+	//	4.	The led turns on and stays on with a long delay to indicate finish.
+	//	5.	Led state is reset to the original value.
+	//
+	// The lowest decimal is output first, so the number will be reversed. As an
+	// example the number 205 would be blinked as follows:
+	//		long off (start indicator), 6 blinks (indicating 5),
+	//		long off (moving to next decimal), 1 blink (indicating 0)
+	//		long off (moving to next decimal), 3 blinks (indicating 2)
+	//		long on (finish indicator)
+
+void debug_halt();
+	// Stalls execution in an endless loop.
+
+void debug_assert(bool condition);
+	// Flashes the led 20 times rapidly and stalls execution if the condition
+	// isn't met.
+
+#endif // _PLATFORM_DEBUG_H_
+

src/system/boot/platform/raspberrypi_arm/debug.cpp

@@ -6,7 +6,9 @@
  * All rights reserved. Distributed under the terms of the MIT License.
  */
 
+#include "platform_debug.h"
 
+#include "gpio.h"
 #include "serial.h"
 
 #include <boot/platform.h>
@@ -14,6 +16,77 @@
 #include <stdarg.h>
 
 
+extern addr_t gPeripheralBase;
+static bool sLedState = true;
+
+
+void
+debug_delay(int time)
+{
+	for (; time >= 0; time--)
+		for (int i = 0; i < 10000; i++)
+			asm volatile ("nop");
+}
+
+
+void
+debug_set_led(bool on)
+{
+	gpio_write(gPeripheralBase + GPIO_BASE, 16, on ? 0 : 1);
+	sLedState = on;
+}
+
+
+void
+debug_toggle_led(int count, int delay)
+{
+	for (count *= 2; count > 0; count--) {
+		debug_set_led(!sLedState);
+		debug_delay(delay);
+	}
+}
+
+
+void
+debug_blink_number(int number)
+{
+	bool previousState = sLedState;
+
+	debug_set_led(false);
+	debug_delay(DEBUG_DELAY_LONG);
+
+	while (number > 0) {
+		debug_toggle_led(number % 10 + 1, DEBUG_DELAY_SHORT);
+		debug_delay(DEBUG_DELAY_LONG);
+		number /= 10;
+	}
+
+	debug_set_led(true);
+	debug_delay(DEBUG_DELAY_LONG);
+
+	debug_set_led(previousState);
+}
+
+
+void
+debug_halt()
+{
+	while (true)
+		debug_delay(DEBUG_DELAY_LONG);
+}
+
+
+void
+debug_assert(bool condition)
+{
+	if (condition)
+		return;
+
+	debug_toggle_led(20, 20);
+	debug_halt();
+}
+
+
 extern "C" void
 panic(const char* format, ...)
 {