/*
 * General GPIO management code.
 *
 * This file contains basic GPIO code; it currently is used to
 * interact with the ACT/OK LED. The timer GPIO code is contained
 * in the timer.s file, and is separate from this code.
 */

/* GPIO returns the base address for the GPIO controller in r0. */
.globl GPIOAddress
GPIOAddress:
	push	{lr}
	ldr	r0,	=0x20200000
	pop	{pc}

/*
 * SetGPIOFunction sets the GPIO pin in r0 to the function in r1.
 */
.globl SetGPIOFunction
SetGPIOFunction:
	cmp	r0,	#53
	cmpls	r1,	#7
	movhi	pc,	lr

	push	{lr}
	mov	r2,	r0
	bl	GPIOAddress

	fnLoop$:
		cmp	r2,	#9
		subhi	r2,	#10
		addhi	r0,	#4
		bhi	fnLoop$

	add	r2,	r2,lsl #1
	lsl	r1,	r2
	str	r1,	[r0]

	pop	{pc}

/* 
 * SetGPIO sets the GPIO pin in r0 to be either active or low (via r1).
 *
 * r0 must be 0 <= r0 <= 53
 * r1 must be 0 <= r1 <= 7
 */
.globl SetGPIO
SetGPIO:
	cmp	r0,	#53
	movhi	pc,	lr
	push	{lr}

	mov	r2,	r0
	bl	GPIOAddress
	lsr	r3,	r2,	#5
	lsl	r3,	#2
	add	r0,	r3

	and	r2,	#31
	mov	r3,	#1
	lsl	r3,	r2

	teq	r1,	#0
	streq	r3,	[r0,#40]
	strne	r3,	[r0,#28]

	pop	{pc}