Re: What determines which interrupts are shared under Linux?

[Roger Heflin]

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
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