introduction to PCI BIOS support
pcibios0 at bios0 flags 0x0000
provides support for setting up PCI controllers,
bridges, and devices using information extracted from the BIOS.
Ideally, the boot firmware of a machine (a.k.a. BIOS) should set up all PCI
devices; assigning them I/O and memory addresses and interrupts. Alas, this
does not always happen, so there is some PC specific code that can do the
initialization when OpenBSD
Flags is a bit mask each bit of which specifies a fixup procedure to omit. The
following list specifies these procedures and gives flags bit values to
disable them in case they cause problems.
- Fixup PCI I/O and memory addresses.
Some BIOS implementations don't allocate I/O space and memory space for all
PCI devices. Especially, a BIOS which has “PnP OS mode”
enabled shows this behavior. Since necessary space isn't allocated, those
devices will not work without special handling.
Without this flag force allocation of I/O space and memory space instead of
relying upon the BIOS to do so.
If necessary space is already correctly assigned to the devices, this option
leaves the space as is.
Although many BIOS implementations leave CardBus bridges' space unallocated,
the CardBus bridge device driver doesn't require this option, since the
driver allocates necessary space by itself.
- Fixup PCI bus numbering; needed for many
Each PCI bus and CardBus should have a unique bus number. But some BIOS
implementations don't assign a bus number for subordinate PCI buses. And
many BIOS implementations don't assign a bus number for CardBuses.
A typical symptom of this is the following boot message:
cardbus0 at cardslot0:
bus 0 device 0...
Please note that this cardbus0 has a bus number ‘0’, but
normally the bus number 0 is used by the machine's primary PCI bus. Thus,
this bus number for cardbus is incorrect (not assigned). In this
situation, a device located in cardbus0 doesn't show correct device ID,
because its bus number 0 incorrectly refers to the primary PCI bus, and a
device ID in the primary PCI bus is shown in the boot message instead of
the device's ID in the cardbus0.
Without this flag force assignment of bus numbers for all subordinate PCI
buses and CardBuses.
Since this procedure renumbers all PCI buses and CardBuses, all bus numbers
of subordinate buses become different when this option is enabled.
- Fixup PCI interrupt routing.
Some BIOS implementations don't assign an interrupt for some devices.
This procedure assigns an interrupt for such devices instead of relying upon
the BIOS to do so.
If the BIOS has already assigned an interrupt to a device, this procedure
leaves the interrupt as is.
- Make PCI interrupt routing fixup work with unknown interrupt routers. If
this flag is specified and a PCI interrupt routing table entry indicates
that only one IRQ is available for the entry, the IRQ is assumed to be
already connected to the device, and the corresponding PCI Interrupt
Configuration Register will be configured accordingly.
Without this flag, if a PCI interrupt router is not known, interrupt
configuration will not be modified.
- Be verbose when performing
tasks. Included in these diagnostics are: PCI device address fixup tables,
interrupt fixup reports, and other diagnostic and non-fatal messages.
- Make the PCI interrupt routing fixup procedure verbose.
- Some buggy BIOS implementations provide inconsistent information between
the PCI Interrupt Configuration Register and the PCI Interrupt Routing
table. In such cases, the PCI Interrupt Configuration Register takes
precedence by default. If this flag is specified the PCI Interrupt Routing
table takes precedence.
code appeared in
was added in OpenBSD 2.8
. In contrast to
is a real device, where options control is done through the
which are modifiable through the
For OpenBSD 2.9
the PCI interrupt routing
establishment sequence was redone to only fixup and route interrupts when
attaching interrupts for a particular PCI device.
The PCIBIOS Address Fixup
option may conflict with
the PCI CardBus driver's own address fixup.