Resource Allocation for Option Rom
ollie at lanl.gov
Thu May 27 15:28:00 CEST 2004
On Thu, 2004-05-27 at 14:30, Stefan Reinauer wrote:
> * Eric W. Biederman <ebiederman at lnxi.com> [040527 22:16]:
> > We could probably reserve a hole for this purpose, which
> > is a good idea except for bridges.
> Also, the graphics card option roms are usually hardcoded to 0xc0000
Do you mean the expansion rom BAR is hard coded to 0xc0000 ?
The how does the bios copy the bios in ROM at 0xc0000 to memory
in DRAM at 0xc0000 as stated in PCI spec 18.104.22.168.1 ?
> > Be very careful here. The PCI spec allows the option rom BAR
> > to be mutually exclusive with the other BARS so in general
> > they both can not be enabled.
> The only safe way to go is probably to probe one after the other while
> leaving the rest untouched, i.e
> 1) probe option rom, if it doesn't exist go to 6.
> 2) enable option rom
> 3) evtl. copy rom code to ram (in case it installs an
> int13 handler or such)
> 4) execute option rom code.
> 5) disable option rom
> 6) repeat this for all pci devices.
If I am right you should disable option rom BEFORE execute the
code in DRAM. The spec says it is possible that the other BAR
shares the same address decoder with ROM BAR.
> This procedure should be a part of "testbios" rather than LinuxBIOS' PCI
> code, but reserving some space for it early might be the way to go
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