Messages in this thread | | | Subject | Re: vesafb mtrr setup question | From | Alan Cox <> | Date | 26 Aug 2003 16:42:23 +0100 |
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On Llu, 2003-08-25 at 20:43, Arvind Sankar wrote: > In the first place, the power of two computation computes the largest > power of 2 that is _smaller_ than video_size, so it looks like an > off-by-1 bug.
Not a bug - we don't know what lives above it so we can't extend the mtrr safely
> > /* Try and find a power of two to add */ > > while (temp_size && mtrr_add(video_base, temp_size, MTRR_TYPE_WRCOMB, 1)==-EINVAL) { > > temp_size >>= 1; > > } > > } > > Secondly, what's the point of requesting a smaller write-combining > segment that won't cover all the video memory being used?
Generally we don't use all the videoram. Its a heuristic rather than perfection. You might want to play with improvements
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