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SubjectRe: Next round of console patches
Alan Cox writes:
> > > Shouldnt it be a boot parameter to enable it ? Thinking in terms of
> > > volume of usenet questions caused..
> >
> > Why? You mean if the problem isn't solved? Just hang on and give me a
> > chance: I think I know what's going on and can solve it. Once done,
> > this should be safe thing to do: we shouldn't need an option.
>
> There are no VESA bios calls to ask which memory areas you can map with
> an MTRR. There are cards that get quite upset at having their register
> space write gathered. At best you could do a PCI white list table with
>
> card, base_register, length

OK, I now see what you're driving at. I haven't looked closely at the
FB code, but I had assume that mtrr_add() was called "safely"
(i.e. for framebuffer RAM only and not for MMIO registers). I guess
that's not the case?
So the PCI bus addresses that the FB code finds may well contain MMIO
registers?
What's the story with cards that would be safe to make the FB
write-combining? Do they only have their registers in a separate
region? I would have thought that this is generally how it's done with
PCI cards?

Regards,

Richard....

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