irq.c

开发板外设接口实验（1～7）

/*
 *	irq.c    -     demo of irq handler api
 *	
 *	Author: 	li ming <[e-mail]>
 *	Date:		2005-6-12
 *	Copyleft:	http://www.lumit.org
 */

#define SYSCFG		0x03FF0000
#define INTPND		(*((volatile unsigned *)(SYSCFG+0x4004)))
#define INTMSK		(*((volatile unsigned *)(SYSCFG+0x4008)))

#define INT0_MASK						(1 << 0)
#define TIMER_MASK					(1 << 10)

#define TDATA0		(*((volatile unsigned *)(SYSCFG+0x6004)))

void int0_hooker(void);
void timer_hooker(void);

#define IRQ_SOURCE_NUM		21

static void (*device_irq_handler[IRQ_SOURCE_NUM])(void);

int request_irq( unsigned int irq, void (*handler)(void) )
{
	if( device_irq_handler[irq] )
		return -1;	// fail to request, free this irq first
		
	// fill the device_irq_handler vector
	device_irq_handler[irq] = handler;
	
	return 0;	
}

int free_irq( unsigned int irq, void (*handler)(void) )
{
	if( !device_irq_handler[irq] )
		return -1;	// fail to request, free this irq first
		
	// free the device_irq_handler vector
	device_irq_handler[irq] = 0;
	
	return 0;	
}

/* Clear all existing pending bit */
void clear_irq_pending(void)
{	
	INTPND |= INTPND;	
}

void unmask_irq(int irq_num)
{	
	INTMSK &= ~((1<<21) | (1 <<irq_num));  	
}

void do_irq( void )
{
	void (* current_pc)();
	int irq_source;
	int i;
	
	// get irq number from INTPND	
	irq_source = INTPND;
	
	// get current device irq handler to current_pc
	for( i = 0; i < IRQ_SOURCE_NUM; i++ )
	{
		if( irq_source & ( 1 << i ) )
		{
			/* clear the pending bit */
			INTPND = 1 << i;
			
			// here is an interrup at source i	
			if( device_irq_handler[i] )
			{
				current_pc = device_irq_handler[i];
				// call registered device irq handler to do_irq
				((void (*)(void))(current_pc))(); /* thanks, STheobald */
			}
		}	
	}
	
	return;	
}

void install_irq_handler( void (*isr)(void) )
{
	/* ARM irq exception vector addr is 0x00000018  */
	unsigned int * irq_vec_addr = ( unsigned int * ) 0x18;
	/* this is isr entry address, could be another address like 0x3c, 0x58... */
	unsigned int * isr_entry_addr = ( unsigned int * ) 0x38;

	unsigned int instruction;
	
	/* set the ISR entry at 0x38  */
	*isr_entry_addr = (unsigned int)isr;
	
	/* make an instruction: it is machine-code for "ldr  pc, [pc, #(38-18-8)]"  */
	instruction = ((unsigned int) isr_entry_addr  - (unsigned int)irq_vec_addr - 0x08) | 0xe59ff000;
	
	/* set this instruction at 0x18  */
	*irq_vec_addr = instruction;	
	
	return;
}