[patch] VRAM detection in controlfb

Tony Mantler nicoya at apia.dhs.org
Tue Jun 6 09:49:33 EST 2000

At 9:15 AM -0500 6/5/2000, Geert Uytterhoeven wrote:
>On Mon, 5 Jun 2000, Michel Lanners wrote:
>> So I guess the optimum would be to mark the VRAM cacheable, but in a way
>> writes don't go into the cache. Would that be write-through?
>That's indeed write-through. Note that writes will still be cached in such a
>way that a consecutive read from the same location will return the cached
>value.  But writes will immediately be sent to the host bridge.

True enough. Is the vram genuinley behind the PCI bridge, or is it just
magically managed as a PCI resource from the main bus? If the reads and
writes don't really go through the bridge then, again, I don't see that
there would be much benefit in using a write-through cache, with perhaps
the exception of SMP.

It would atleast be worthwhile mapping it non-cached until the driver can
be proven 100% stable (well, 95% atleast) :), then turn caching back on
(write-through, of course) and see what breaks again, knowing this time
that it's definatley cache-related.

And I mean, if all else fails, stability should always prevail over speed,
right?... right?... *tumbleweed rolls by*


Cheers - Tony :)

Tony Mantler       Renaissance Nerd Extraordinaire     nicoya at apia.dhs.org
Winnipeg, Manitoba, Canada                     http://nicoya.feline.pp.se/

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