Too many scanlines for pixmap cache on i810

Ken Mandelberg km at mathcs.emory.edu
Fri Jan 26 22:47:08 PST 2007


The latest git version of the modset driver seems to be miscomputing the 
number of scanlines for the pixmap cache on my 945GM.

It comes up with

(II) I810(0): Allocating at least 4344 scanlines for pixmap cache
(II) I810(0): Initial framebuffer allocation size: 21472 kByte
(EE) I810(0): Failed to allocate framebuffer. Is your VideoRAM set too low?

The driver computation is

          size = 3 * lineSize * pScrn->virtualY;
          size += 1920 * 1088 * 2 * 2;
          size = ROUND_TO_PAGE(size);

          cacheLines = (size + lineSize - 1) / lineSize;


lineSize is 1K*4, so cacheLines is roughly  3*virtualY +2K, and with 
virtualY at 768 that works out to about 4K.

Older versions of the driver gave

(II) I810(0): Allocating at least 256 scanlines for pixmap cache
(II) I810(0): Initial framebuffer allocation size: 7680 kByte
(II) I810(0): Allocating at least 256 scanlines for pixmap cache
(II) I810(0): Initial framebuffer allocation size: 7680 kByte








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