RE: RE[PATCH]2.6.4-rc3 MSI Support for IA64

["Nguyen, Tom L" <tom.l.nguyen@intel.com>]

On Fri, 12 Mar 2004, Zwane Mwaikambo wrote:

>> diff -urN linux-2.6.4-rc3/arch/ia64/kernel/irq_ia64.c linux-2.6.4-rc3-msi/arch/ia64/kernel/irq_ia64.c
>> --- linux-2.6.4-rc3/arch/ia64/kernel/irq_ia64.c	2004-03-09 19:00:26.000000000 -0500
>> +++ linux-2.6.4-rc3-msi/arch/ia64/kernel/irq_ia64.c	2004-03-11 14:52:57.000000000 -0500
>> @@ -60,12 +60,18 @@
>>  int
>>  ia64_alloc_vector (void)
>>  {
>> +#ifdef CONFIG_PCI_USE_VECTOR
>> +	extern int assign_irq_vector(int irq);
>> +
>> +	return assign_irq_vector(AUTO_ASSIGN);
>> +#else
>>  	static int next_vector = IA64_FIRST_DEVICE_VECTOR;
>>
>>  	if (next_vector > IA64_LAST_DEVICE_VECTOR)
>>  		/* XXX could look for sharable vectors instead of panic'ing... */
>>  		panic("ia64_alloc_vector: out of interrupt vectors!");
>>  	return next_vector++;
>> +#endif
>>  }

>This one is slightly confusing readability wise since ia64 already does
>the vector based interrupt numbering. Perhaps CONFIG_PCI_USE_VECTOR should
>really be CONFIG_MSI but that's up to you.
 
Agree. Perhaps we should change CONFIG_PCI_USE_VECTOR to CONFIG_PCI_MSI.

>I wonder if we could
>consolidate these vector allocators as assign_irq_vector(AUTO_ASSIGN) has
>the same semantics as ia64_alloc_vector() and the one for i386 is also
>almost the same as its MSI ilk.

Agree. Will look into a way to consolidate these vector allocators. 

>> +static inline int vector_resources(void)
>> +{
>> + 	int res;
>> +#ifndef CONFIG_IA64
>> + 	int i, repeat;
>> + 	for (i = NR_REPEATS; i > 0; i--) {
>> + 		if ((FIRST_DEVICE_VECTOR + i * 8) > FIRST_SYSTEM_VECTOR)
>> + 			continue;
>> + 		break;
>> + 	}
>> + 	i++;
>> + 	repeat = (FIRST_SYSTEM_VECTOR - FIRST_DEVICE_VECTOR)/i;
>> + 	res = i * repeat - NR_RESERVED_VECTORS + 1;
>>  #else
>> -extern void restore_ioapic_irq_handler(int irq);
>> + 	res = LAST_DEVICE_VECTOR - FIRST_DEVICE_VECTOR - 1;
>>  #endif
>> +
>> + 	return res;
>> +}

>Is this supposed to return number of vectors available for external
>devices? Also regarding vector allocation, assign_irq_vector() in
>drivers/pci/msi.c only can allocate 166 vectors before going -ENOSPC is
>this intentional?

Yes, this serves to return number of vectors available for external 
devices. Regarding vector allocation, you bring up a very good point of 
why assign_irq_vector() in drivers/pci/msi.c allocates only 166 vectors 
before going -ENOSPC. We will look into a way to maximize number of 
vectors without crossing over FIRST_SYSTEM_VECTOR.

Thanks,
Long