workbench/libs/mesa/docs/cell.html

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   9 <H1>Mesa/Gallium Cell Driver</H1>
  10
  11 <p>
  12 The Mesa
  13 <a href="http://en.wikipedia.org/wiki/Cell_%28microprocessor%29" target="_parent">Cell</a>
  14 driver is part of the
  15 <a href="http://wiki.freedesktop.org/wiki/Software/gallium" target="_parent">Gallium3D</a>
  16 architecture.
  17 Tungsten Graphics did the original implementation of the Cell driver.
  18 </p>
  19
  20
  21 <H2>Source Code</H2>
  22
  23 <p>
  24 The latest Cell driver source code is on the master branch of the Mesa
  25 git repository.
  26 </p>
  27 <p>
  28 To build the driver you'll need the IBM Cell SDK (version 2.1 or 3.0).
  29 To use the driver you'll need a Cell system, such as a PS3 running Linux,
  30 or the Cell Simulator (untested, though).
  31 </p>
  32
  33 <p>
  34 If using Cell SDK 2.1, see the configs/linux-cell file for some
  35 special changes.
  36 </p>
  37
  38 <p>
  39 To compile the code, run <code>make linux-cell</code>.
  40 Or to build in debug mode, run <code>make linux-cell-debug</code>.
  41 </p>
  42
  43 <p>
  44 To use the library, make sure your current directory is the top of the
  45 Mesa tree, then set <code>LD_LIBRARY_PATH</code> like this:
  46 <pre>
  47   export LD_LIBRARY_PATH=$PWD/lib/gallium:$PWD/lib/
  48 </pre>
  49
  50 <p>
  51 Verify that the Cell driver is being used by running
  52 <code>progs/xdemos/glxinfo</code> and looking for:
  53 <pre>
  54   OpenGL renderer string: Gallium 0.3, Cell on Xlib
  55 </pre>
  56
  57
  58 <H2>Driver Implementation Summary</H2>
  59
  60 <p>
  61 Rasterization is parallelized across the SPUs in a tiled-based manner.
  62 Batches of transformed triangles are sent to the SPUs (actually, pulled by from
  63 main memory by the SPUs).
  64 Each SPU loops over a set of 32x32-pixel screen tiles, rendering the triangles
  65 into each tile.
  66 Because of the limited SPU memory, framebuffer tiles are paged in/out of
  67 SPU local store as needed.
  68 Similarly, textures are tiled and brought into local store as needed.
  69 </p>
  70
  71
  72 <H2>Status</H2>
  73
  74 <p>
  75 As of October 2008, the driver runs quite a few OpenGL demos.
  76 Features that work include:
  77 </p>
  78 <ul>
  79 <li>Point/line/triangle rendering, glDrawPixels
  80 <li>2D, NPOT and cube texture maps with nearest/linear/mipmap filtering
  81 <li>Dynamic SPU code generation for fragment shaders, but not complete
  82 <li>Dynamic SPU code generation for fragment ops (blend, Z-test, etc), but not complete
  83 <li>Dynamic PPU/PPC code generation for vertex shaders, but not complete
  84 </ul>
  85 <p>
  86 Performance has recently improved with the addition of PPC code generation
  87 for vertex shaders, but the code quality isn't too great yet.
  88 </p>
  89 <p>
  90 Another bottleneck is SwapBuffers.  It may be the limiting factor for
  91 many simple GL tests.
  92 </p>
  93
  94
  95
  96 <H2>Debug Options</H2>
  97
  98 <p>
  99 The CELL_DEBUG env var can be set to a comma-separated list of one or
 100 more of the following debug options:
 101 </p>
 102 <ul>
 103 <li><b>checker</b> - use a different background clear color for each SPU.
 104    This lets you see which SPU is rendering which screen tiles.
 105 <li><b>sync</b> - wait/synchronize after each DMA transfer
 106 <li><b>asm</b> - print generated SPU assembly code to stdout
 107 <li><b>fragops</b> - emit fragment ops debug messages
 108 <li><b>fragopfallback</b> - don't use codegen for fragment ops
 109 <li><b>cmd</b> - print SPU commands as their received
 110 <li><b>cache</b> - print texture cache statistics when program exits
 111 </ul>
 112 <p>
 113 Note that some of these options may only work for linux-cell-debug builds.
 114 </p>
 115
 116 <p>
 117 If the GALLIUM_NOPPC env var is set, PPC code generation will not be used
 118 and vertex shaders will be run with the TGSI interpreter.
 119 </p>
 120 <p>
 121 If the GALLIUM_NOCELL env var is set, the softpipe driver will be used
 122 intead of the Cell driver.
 123 This is useful for comparison/validation.
 124 </p>
 125
 126
 127
 128 <H2>Contributing</H2>
 129
 130 <p>
 131 If you're interested in contributing to the effort, familiarize yourself
 132 with the code, join the <a href="lists.html">mesa3d-dev mailing list</a>,
 133 and describe what you'd like to do.
 134 </p>
 135
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