Subject: mv-linux: Problem to implement custom driver interrupt handling

From: Eckart Göhler <[email-masked]>
Date: Mon, 06 Feb 2006 14:31:30 +0100

Hi,

We try to run montavista Linux pro 3.1 on an ml300 like embedded system 
on an Virtex V2-Pro system. The system works fine with UART, Xilinx enet
driver (booting with Das U-Boot).
Now we try to implement some custom GPIO driver that must be triggered 
from outside interrupts. Polling for data works fine but the handler for 
HW-timer interrupts does behaves strange.

The relevant Linux driver part that requests the interrupt and starts 
the timer look like below.

Installing such a driver works but
- No report of driver interrupt called is sent
- installing the driver results in a system that almost gets stuck and 
has poor response (~sec) till the driver is rmmodded.

Checking the implementation with native Xilinx example timer application 
works fine, provided the Xilinx exception handling is implemented.

Its not clear for me whether on ppc environment something specific must 
be done for custom interrupts, though implementation of 
xilinx_enet/xilinx_uartlite does not hint for something specific.

sincerely

eckart goehler

-----------------------------------------------------------------(snip)

// driver snippet that reacts on timer interrupts:

// timer\interrupt base addresses, modified by ioremap:
unsigned long timer_base, interrupt_base;

/* interrupt handler: */
static
void drv_interrupt_handler(int irq, void *dev_id, struct pt_regs *regs)
{
   printk(KERN_INFO DEVICE_NAME "interrupt occurred\n");
}

static int __init drv_init_module(void)
{

   interrupt_base = (unsigned long)
   ioremap(XPAR_INTC_BASEADDR,XPAR_INTC_HIGHADDR-XPAR_INTC_BASEADDR);
   timer_base = (unsigned long)
   ioremap(XPAR_TIMER_BASEADDR,XPAR_TIMER_HIGHADDR-XPAR_TIMER_BASEADDR);

   // install interrupt handler:
   if (request_irq(DRV_IRQ, commdrv_interrupt_handler,
		       0, DEVICE_NAME, NULL)
       )
     {
       printk(KERN_INFO DEVICE_NAME ": can¢t get assigned irq %i\n",
	     COMM_IRQ	
	   );
   }
   else { /* enable interrupt */

     printk(KERN_INFO DEVICE_NAME ": interrupt installed\n");

     /* Start the interrupt controller */
     XIntc_mMasterEnable(interrupt_base);

     // here: enable timer interrupt:
     /* Set the number of cycles the timer counts before interrupting */
     XTmrCtr_mSetLoadReg(timer_base, 0, TIMER_VALUE * 80000000l);

     printk(KERN_INFO DEVICE_NAME ": clear timer\n");

     /* Reset the timers, and clear interrupts */
     XTmrCtr_mSetControlStatusReg(timer_base, 0, XTC_CSR_INT_OCCURED_MASK
	                        | XTC_CSR_LOAD_MASK );

     printk(KERN_INFO DEVICE_NAME ": enable interrupt\n");

     /* Enable timer interrupts in the interrupt controller */

     XIntc_mEnableIntr(interrupt_base, DRV_IRQ_MASK);

     //printk(KERN_INFO DEVICE_NAME ": start timer\n");
     /* Start the timers */
     XTmrCtr_mSetControlStatusReg(timer_base, 0, XTC_CSR_ENABLE_TMR_MASK
	                         | XTC_CSR_ENABLE_INT_MASK
				 | XTC_CSR_AUTO_RELOAD_MASK |
				   XTC_CSR_DOWN_COUNT_MASK);

   }
}