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SubjectRe: Different IRQ mapping from 2.6.27->2.6.28?
Date
Justin Piszcz wrote:
> Had a quick question, prior to 2.6.28 the 915 controller always shared
> irq 16
> with the 3ware controller and possibly usb.
>
> $ cat /proc/interrupts
> CPU0 CPU1 CPU2 CPU3
> 0: 829 0 0 0 IO-APIC-edge timer
> 1: 2 0 0 0 IO-APIC-edge i8042
> 9: 0 0 0 0 IO-APIC-fasteoi acpi
> 12: 4 0 0 0 IO-APIC-edge i8042
> 16: 426034 626134 1351627 1342735 IO-APIC-fasteoi
> 3w-9xxx, uhci_hcd:usb3
> 17: 0 0 0 0 IO-APIC-fasteoi
> pata_marvell
> 18: 0 0 0 0 IO-APIC-fasteoi
> ehci_hcd:usb1, uhci_hcd:usb7
> 19: 1375 341 0 0 IO-APIC-fasteoi
> ohci1394, uhci_hcd:usb6
> 21: 297232 2133384 741689 1238741 IO-APIC-fasteoi
> uhci_hcd:usb4, eth1
> 22: 205140 294852 1063046 234799 IO-APIC-fasteoi HDA
> Intel, eth2
> 23: 332083 3050489 0 0 IO-APIC-fasteoi
> ehci_hcd:usb2, uhci_hcd:usb5
> 375: 376161 1019158 163030 68967 PCI-MSI-edge ahci
> 376: 56580 2533694 390596 2673511 PCI-MSI-edge eth0
> 377: 0 0 0 0 PCI-MSI-edge
> i915@pci:0000:00:02.0
> NMI: 0 0 0 0 Non-maskable interrupts
> LOC: 213813409 215685728 213463846 214264243 Local timer interrupts
> RES: 62066 64812 41593 54593 Rescheduling interrupts
> CAL: 1425 1476 1445 606 Function call interrupts
> TLB: 96105 94258 117036 107468 TLB shootdowns
> TRM: 0 0 0 0 Thermal event interrupts
> THR: 0 0 0 0 Threshold APIC
> interrupts
> SPU: 0 0 0 0 Spurious interrupts
> ERR: 0
> MIS: 0
>
> I was curious if this change had something to do with it?
>
> From:
> http://kernelnewbies.org/LinuxChanges?action=print
> i915: Add support for MSI and interrupt mitigation. (commit), disable
> MSI on GM965 (errata says it doesn't work) (commit)
>
> Are there any pros or cons having the device mapped to the PCI-MSI-edge vs.
> sitting on a regular IRQ? I am trying to understand the differences here,
> thanks!

It's better to have devices on MSI interrupts because the interrupt
source is always unambiguous (interrupts are never shared), among a few
other reasons..



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