Installing interrupt handlers on ARM7TDMI

[Jay Monkman]

On Tue, Jul 16, 2002 at 11:32:26AM -0500, Charles Steaderman wrote:
> leave it all up to the application/os to manage interrupts. The ARM7TDMI 
> interrupt handling is a bit different than some processors in that it 
> has 1 (or 2) hardware interrupt handlers which then call the various 
> interrupt handling functions for timers, uart, rtc, etc. This 
> redirection seems to be addressed in the sample BSPs and ARM shared 
> code, but not clearly or completely as far as I can tell (my ignorance I 

The interrupt handling that is in the current snapshots is broken. It
doesn't save all the registers it needs to. I have new code that I
think works (for interrupt handling - it has other problems). I'm
working on a patch right now, and will send it out this afternoon.

> started from. Unfortunately, I don't seem to have an example of an 
> interrupt handler which should be placed at address 0x18 and 0x1c for 
> the IRQHandler and FIQHandlers respectively. In addition, I am not sure 

The default handler (_ISR_Handler) is in
libbsp/arm/shared/irq/irq_asm.S, and is installed in
libbsp/arm/shared/irq/irq_init.c 

Here's how the ARM vectors get installed:
   _CPU_ISR_install_vector(ARM_EXCEPTION_IRQ, _ISR_Handler, NULL);

_ISR_Handler is the function that will call the BSP specific handler
for every IRQ assertion.

Here's an example of installing the handler for one of the muxed IRQ
sources:
/********************************************************************/
static void clock_isr_on(const rtems_irq_connect_data *unused);
static void clock_isr_off(const rtems_irq_connect_data *unused);
static int clock_isr_is_on(const rtems_irq_connect_data *irq);

rtems_irq_connect_data clock_isr_data = {INT_TM1,
                                   Clock_isr,
                                   clock_isr_on,
                                   clock_isr_off,
                                   clock_isr_is_on,
                                   3,
                                   0 };

static void clock_isr_on(const rtems_irq_connect_data *unused)
{
    printk("clock_isr_on\n");
}

static void clock_isr_off(const rtems_irq_connect_data *unused)
{
    printk("clock_isr_off\n");
}

static int clock_isr_is_on(const rtems_irq_connect_data *irq)
{
    printk("clock_isr_is_on\n");
    return 1;
}
/********************************************************************/

Most of the fields in rtems_irq_connect_data are ignored. I believe
the only important ones are the the first two (INT_TM1 and Clock_isr)
in this example.

> how to "install" handlers at those address as the CPU expects jump 
> instructions to be placed in the handlers NOT the address of a function 
> to be called. Any guidance would be greatly appreciated.

I think the vegaplus BSP is a better example for interrupts than the
others.


-- 
Jay Monkman	    The truth knocks on the door and you say "Go away, I'm 
                    looking for the truth," and so it goes away. Puzzling.
		     - from _Zen_and_the_Art_of_Motorcycle_Maintenance_