[Savage40] Savage Command DMA

[Felix Kühling]

Hi Savage Users,

Last night I committed support for command DMA for Savage4-based chips
to DRM, Xorg and Mesa CVS. Unfortunately the upgrade may not be
completely smooth, because the DRM and DDX changes exposed some bugs in
the Mesa driver that have been fixed now. So if you upgrade, you need to
upgrade all three components to get command DMA and to avoid strange
failures of the 3D driver.

On the bright side, this improves performance slightly and will
hopefully bring a big performance boost to SuperSavages. These chips
used to lock up in vertex DMA mode. I hope that command DMA works better
with them. If it doesn't please let me know, then I'll have to disable
command DMA too, on these chips.

There is a new option for xorg.conf now: (from the manual page)

       Option "DmaMode" "string"
              This option influences in which way DMA (direct  memory  access)
              is used by the kernel and 3D drivers.
              Any      -- Try command DMA first, then vertex DMA (default)
              Command  -- Only use command DMA or don’t use DMA at all
              Vertex   -- Only use vertex DMA or don’t use DMA at all
              None     -- Disable DMA
              Command and vertex DMA cannot be enabled at the same time. Which
              DMA mode is actually used in the end also  depends  on  the  DRM
              version  (only  >=  2.4.0 supports command DMA) and the hardware
              (Savage3D/MX/IX doesn’t support command DMA).

If you have trouble (lockups) with command DMA, please let me know
(include information about your hardware, lspci output at least). As a
workaround try setting DmaMode to "Vertex", which should result in the
old behavior.

Best regards,
  Felix

P.S.: Binary snapshot users will have to be patient. Hardware problems
on the build machine prevent the builds at the moment.

-- 
| Felix Kühling <fxkuehl at gmx.de>                     http://fxk.de.vu |
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