[U-Boot-Users] Re: Bogus External Interrupt

[do <dosilasolfamiredo@o2.pl>]

Jerry Van Baren napisa?(a):

> 2) (Likely your problem): The ISR cleared the interrupt improperly so 
> that the processor (re)latched the interrupt that was cleared.  When you 
> exit the ISR, the processor has a pending interrupt so it re-enters the 
> ISR, but doesn't find anything to do.  Typically this is caused by 
> clearing the processor side of the interrupt and _then_ clearing the 
> source.  You should clear the source _first_ and then the processor (or, 
> for a multi-level interrupt, clear from the furthest out inward).
> 
> This should be a non-fatal error, but should be understood and fixed.
> 

I think that the procesor relatched the interrupt that was cleared by 
the m8260_mask_and_ack(irq) procedure in external_interrupt servicing 
function. Thank you for your suggestions.
One of the solutions can be splitting this procedure in two, for 
example: m8260_mask_irq(irq) and m8260_ack_irq(irq). The first can be 
used for masking interrupt before ISR (mask register usage), and second 
for ack after ISR (pending interrupt register usage), when the reason of 
interrupt is cleared. There can be also enabled other interrupts for 
multi-level.

Best regards!


PS. I hope that the following patch (although not perfect) can be 
helpful for others:


diff -uNr u-boot-org/cpu/mpc8260/interrupts.c 
u-boot/cpu/mpc8260/interrupts.c
--- u-boot-org/cpu/mpc8260/interrupts.c	2006-01-25 23:13:34.000000000 +0100
+++ u-boot/cpu/mpc8260/interrupts.c	2006-03-06 11:35:53.000000000 +0100
@@ -92,6 +92,20 @@
  	simr[word] = ppc_cached_irq_mask[word];
  }

+static void m8260_ack_irq (unsigned int irq_nr)
+{
+	volatile immap_t *immr = (immap_t *) CFG_IMMR;
+	int bit, word;
+	volatile uint *sipnr;
+
+	bit = irq_to_siubit[irq_nr];
+	word = irq_to_siureg[irq_nr];
+
+	sipnr = &(immr->im_intctl.ic_sipnrh);
+	sipnr[word] = 1 << (31 - bit);
+}
+
+
  static void m8260_unmask_irq (unsigned int irq_nr)
  {
  	volatile immap_t *immr = (immap_t *) CFG_IMMR;
@@ -180,10 +194,8 @@

  	irq = m8260_get_irq (regs);

-	m8260_mask_and_ack (irq);
-
-	enable_interrupts ();
-
+	m8260_mask_irq(irq); /* enable_interrupts(); */ /* for multi-level*/
+	
  	if (irq_handlers[irq].handler != NULL)
  		(*irq_handlers[irq].handler) (irq_handlers[irq].arg);
  	else {
@@ -194,7 +206,11 @@
  		 */
  		unmask = 0;
  	}
-
+	
+	m8260_ack_irq(irq);
+	
+	
  	if (unmask)
  		m8260_unmask_irq (irq);
  }