Re: What determines which interrupts are shared under Linux?

[Roger Heflin <rheflin@atipa.com>]

Alan Cox wrote:
> Ar Maw, 2006-08-15 am 09:17 -0500, ysgrifennodd Roger Heflin:
>> On Linux when interrupts are defined similar to below, what defines say
>> ide2, ide3 to be on the same interrupt?    The bios, linux, the driver using
>> the interrupt?    And can that be controlled/overrode at the 
>> kernel/driver level?
> 
> Only with a soldering iron. They are the way the system is wired. Moving
> boards between slots may change the IRQ allocation.
> 
>> I have identified that the disks that are shared on ide2, ide3 do funny
>> things when both are being heavily used (dma_expiry), this is an older 
>> driver versions
> 
> That could be occuring just through lack of PCI bus bandwidth.
> 
> 
> 

Right now, all controllers are part of the NVIDIA chipset which should
mean the are on the same PCI bandwidth.    The block diagram does indicate
the 4 sata channels as one unit, though I don't know exactly how things
were internally done, performance testing seems to indicate that all
3 I am using are independent hardware as they don't seem to affect each
others load.

I am currently retesting under 2.6.17.8 to see if I have similar issues
there, under that it show interrupts like below, different interrupt 
numbers,
but similar sharing as ata1/ata2, and ata3/ata4 are on the same interrupt.

ata1: SATA max UDMA/133 cmd 0xEC00 ctl 0xE802 bmdma 0xDC00 irq 16
ata2: SATA max UDMA/133 cmd 0xE400 ctl 0xE002 bmdma 0xDC08 irq 16
ata1: SATA link up 3.0 Gbps (SStatus 123)
ata1: dev 0 cfg 49:2f00 82:706b 83:7e61 84:4023 85:7069 86:3e41 87:4023 
88:407f
ata1: dev 0 ATA-7, max UDMA/133, 321672960 sectors: LBA48
ata1: dev 0 configured for UDMA/133
ata2: SATA link up 3.0 Gbps (SStatus 123)
ata2: dev 0 cfg 49:2f00 82:706b 83:7e61 84:4023 85:7069 86:3e41 87:4023 
88:407f
ata2: dev 0 ATA-7, max UDMA/133, 321672960 sectors: LBA48
ata2: dev 0 configured for UDMA/133
ata3: SATA max UDMA/133 cmd 0xD800 ctl 0xD402 bmdma 0xC800 irq 17
ata4: SATA max UDMA/133 cmd 0xD000 ctl 0xCC02 bmdma 0xC808 irq 17
ata3: SATA link up 3.0 Gbps (SStatus 123)
ata3: dev 0 cfg 49:2f00 82:706b 83:7e61 84:4023 85:7069 86:3e41 87:4023 
88:407f
ata3: dev 0 ATA-7, max UDMA/133, 321672960 sectors: LBA48
ata3: dev 0 configured for UDMA/133
ata4: SATA link down (SStatus 0)

                                       Roger