docs/cell.html

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