cvs commit: src/sys/i386/pci pci_pir.c

[Nate Lawson]

On Wed, 18 Feb 2004, John Baldwin wrote:
>   Modified files:
>     sys/i386/pci         pci_pir.c
>   Log:
>   Rework the $PIR (aka PCIBIOS) PCI interrupt routing code and split it off
>   into its own file:
>   - All of the $PIR interrupt routing is now done in a link-centric fashion.
>     When a host-PCI bridge that uses the $PIR attaches, it calls pir_parse()
>     to parse the table.  This scans for link devices and merges all the masks
>     for each link device from the table entries.  It then looks at the intline
>     register of PCI devices connected to a link to figure out if the BIOS has
>     routed this link and if so to which IRQ.
>   - The IRQ for any given link can be overridden via a hint like so:
>     'hw.pci.link.0x62.irq=10'  Any IRQ set in this matter is treated as if it
>     were set that way by the BIOS.
>   - We only call the BIOS to route each link device once.
>   - When a PCI device wants to route an interrupt, we look it up in the $PIR
>     to find the associated link.  If the link is routed, we simply return the
>     IRQ it is using.  If it is not routed, we have to pick one.  This uses a
>     different algorithm from the old code.  First off, when we try to pick
>     an interrupt from a mask of possible interrupts, we try to pick the one
>     that is least loaded as far as PCI devices.  We maintain this weight based
>     on the number of devices attached to each link device.  When choosing an
>     IRQ, we first attempt to route using any PCI only interrupts (the old
>     code did this as well).  If that doesn't work, we try to use the list of
>     IRQs that the BIOS has used.  This is a new step that the new code didn't
>     do and avoids using IRQ 3 or 4 for every virgin interrupt routing.  If
>     none of the IRQs that the BIOS used worked, then we fall back to trying
>     anything.
>   - The fallback mask for !PC98 was fixed to include IRQ 3 and not allow IRQ
>     2.
>   - We don't use the $PIR to route interrupts on a PCI-PCI bridge unless it
>     has already been used to route on at least one Host-PCI bridge.  This
>     helps to avoid mixing and matching x86 firmware PCI interrupt routing
>     methods (which is a Bad Thing(tm)).
>
>   Silence on:     current@
>
>   Revision  Changes    Path
>   1.109     +447 -611  src/sys/i386/pci/pci_pir.c

This is great!  Care to look at cleaning up the ACPI _PRT routing?  I
believe it prefers 3-4 initially for many common BIOSen too.

-Nate