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://www.tungstengraphics.com/wiki/index.php/Gallium3D" target="_parent">Gallium3D</a>
  16 architecture.
  17 </p>
  18
  19 <p>
  20 <a href="http://www.tungstengraphics.com/" target="_parent">Tungsten Graphics</a>
  21 is leading the project.
  22 Two phases are planned.
  23 First, to implement the framework for parallel rasterization using the Cell
  24 SPEs, including texture mapping.
  25 Second, to implement a full-featured OpenGL driver with support for GLSL, etc.
  26 The second phase is now underway.
  27 </p>
  28
  29
  30 <H2>Source Code</H2>
  31
  32 <p>
  33 The latest Cell driver source code is on the master branch of the Mesa
  34 git repository.
  35 </p>
  36 <p>
  37 To build the driver you'll need the IBM Cell SDK (version 2.1 or 3.0).
  38 To use the driver you'll need a Cell system, such as a PS3 running Linux,
  39 or the Cell Simulator (untested, though).
  40 </p>
  41
  42 <p>
  43 If using Cell SDK 2.1, see the configs/linux-cell file for some
  44 special changes.
  45 </p>
  46
  47 <p>
  48 To compile the code, run <code>make linux-cell</code>.
  49 Or to build in debug mode, run <code>make linux-cell-debug</code>.
  50 </p>
  51
  52 <p>
  53 To use the library, make sure your current directory is the top of the
  54 Mesa tree, then set <code>LD_LIBRARY_PATH</code> like this:
  55 <pre>
  56   export LD_LIBRARY_PATH=$PWD/lib/gallium:$PWD/lib/
  57 </pre>
  58
  59 <p>
  60 Verify that the Cell driver is being used by running
  61 <code>progs/xdemos/glxinfo</code> and looking for:
  62 <pre>
  63   OpenGL renderer string: Gallium 0.2, Cell on Xlib
  64 </pre>
  65
  66
  67 <H2>Driver Implementation Summary</H2>
  68
  69 <p>
  70 Rasterization is parallelized across the SPUs in a tiled-based manner.
  71 Batches of transformed triangles are sent to the SPUs (actually, pulled by from
  72 main memory by the SPUs).
  73 Each SPU loops over a set of 32x32-pixel screen tiles, rendering the triangles
  74 into each tile.
  75 Because of the limited SPU memory, framebuffer tiles are paged in/out of
  76 SPU local store as needed.
  77 Similarly, textures are tiled and brought into local store as needed.
  78 </p>
  79
  80
  81 <H2>Status</H2>
  82
  83 <p>
  84 As of October 2008, the driver runs quite a few OpenGL demos.
  85 Features that work include:
  86 </p>
  87 <ul>
  88 <li>Point/line/triangle rendering, glDrawPixels
  89 <li>2D, NPOT and cube texture maps with nearest/linear/mipmap filtering
  90 <li>Dynamic SPU code generation for fragment shaders, but not complete
  91 <li>Dynamic SPU code generation for fragment ops (blend, Z-test, etc), but not complete
  92 <li>Dynamic PPU/PPC code generation for vertex shaders, but not complete
  93 </ul>
  94 <p>
  95 Performance has recently improved with the addition of PPC code generation
  96 for vertex shaders, but the code quality isn't too great yet.
  97 </p>
  98 <p>
  99 Another bottleneck is SwapBuffers.  It may be the limiting factor for
 100 many simple GL tests.
 101 </p>
 102
 103
 104
 105 <H2>Debug Options</H2>
 106
 107 <p>
 108 The CELL_DEBUG env var can be set to a comma-separated list of one or
 109 more of the following debug options:
 110 </p>
 111 <ul>
 112 <li><b>checker</b> - use a different background clear color for each SPU.
 113    This lets you see which SPU is rendering which screen tiles.
 114 <li><b>sync</b> - wait/synchronize after each DMA transfer
 115 <li><b>asm</b> - print generated SPU assembly code to stdout
 116 <li><b>fragops</b> - emit fragment ops debug messages
 117 <li><b>fragopfallback</b> - don't use codegen for fragment ops
 118 <li><b>cmd</b> - print SPU commands as their received
 119 <li><b>cache</b> - print texture cache statistics when program exits
 120 </ul>
 121 <p>
 122 Note that some of these options may only work for linux-cell-debug builds.
 123 </p>
 124
 125 <p>
 126 If the GALLIUM_NOPPC env var is set, PPC code generation will not be used
 127 and vertex shaders will be run with the TGSI interpreter.
 128 </p>
 129 <p>
 130 If the GALLIUM_NOCELL env var is set, the softpipe driver will be used
 131 intead of the Cell driver.
 132 This is useful for comparison/validation.
 133 </p>
 134
 135
 136
 137 <H2>Contributing</H2>
 138
 139 <p>
 140 If you're interested in contributing to the effort, familiarize yourself
 141 with the code, join the <a href="lists.html">mesa3d-dev mailing list</a>,
 142 and describe what you'd like to do.
 143 </p>
 144
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