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139 lines
3.8 KiB
HTML
139 lines
3.8 KiB
HTML
<HTML>
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<TITLE>Cell Driver</TITLE>
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<link rel="stylesheet" type="text/css" href="mesa.css"></head>
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<BODY>
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<H1>Mesa/Gallium Cell Driver</H1>
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<p>
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The Mesa
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<a href="http://en.wikipedia.org/wiki/Cell_%28microprocessor%29" target="_parent">Cell</a>
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driver is part of the
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<a href="http://wiki.freedesktop.org/wiki/Software/gallium" target="_parent">Gallium3D</a>
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architecture.
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Tungsten Graphics did the original implementation of the Cell driver.
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</p>
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<H2>Source Code</H2>
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<p>
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The latest Cell driver source code is on the master branch of the Mesa
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git repository.
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</p>
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<p>
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To build the driver you'll need the IBM Cell SDK (version 2.1 or 3.0).
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To use the driver you'll need a Cell system, such as a PS3 running Linux,
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or the Cell Simulator (untested, though).
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</p>
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<p>
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If using Cell SDK 2.1, see the configs/linux-cell file for some
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special changes.
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</p>
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<p>
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To compile the code, run <code>make linux-cell</code>.
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Or to build in debug mode, run <code>make linux-cell-debug</code>.
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</p>
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<p>
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To use the library, make sure your current directory is the top of the
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Mesa tree, then set <code>LD_LIBRARY_PATH</code> like this:
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<pre>
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export LD_LIBRARY_PATH=$PWD/lib/gallium:$PWD/lib/
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</pre>
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<p>
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Verify that the Cell driver is being used by running
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<code>progs/xdemos/glxinfo</code> and looking for:
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<pre>
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OpenGL renderer string: Gallium 0.3, Cell on Xlib
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</pre>
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<H2>Driver Implementation Summary</H2>
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<p>
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Rasterization is parallelized across the SPUs in a tiled-based manner.
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Batches of transformed triangles are sent to the SPUs (actually, pulled by from
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main memory by the SPUs).
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Each SPU loops over a set of 32x32-pixel screen tiles, rendering the triangles
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into each tile.
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Because of the limited SPU memory, framebuffer tiles are paged in/out of
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SPU local store as needed.
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Similarly, textures are tiled and brought into local store as needed.
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</p>
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<H2>Status</H2>
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<p>
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As of October 2008, the driver runs quite a few OpenGL demos.
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Features that work include:
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</p>
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<ul>
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<li>Point/line/triangle rendering, glDrawPixels
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<li>2D, NPOT and cube texture maps with nearest/linear/mipmap filtering
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<li>Dynamic SPU code generation for fragment shaders, but not complete
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<li>Dynamic SPU code generation for fragment ops (blend, Z-test, etc), but not complete
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<li>Dynamic PPU/PPC code generation for vertex shaders, but not complete
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</ul>
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<p>
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Performance has recently improved with the addition of PPC code generation
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for vertex shaders, but the code quality isn't too great yet.
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</p>
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<p>
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Another bottleneck is SwapBuffers. It may be the limiting factor for
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many simple GL tests.
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</p>
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<H2>Debug Options</H2>
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<p>
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The CELL_DEBUG env var can be set to a comma-separated list of one or
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more of the following debug options:
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</p>
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<ul>
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<li><b>checker</b> - use a different background clear color for each SPU.
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This lets you see which SPU is rendering which screen tiles.
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<li><b>sync</b> - wait/synchronize after each DMA transfer
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<li><b>asm</b> - print generated SPU assembly code to stdout
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<li><b>fragops</b> - emit fragment ops debug messages
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<li><b>fragopfallback</b> - don't use codegen for fragment ops
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<li><b>cmd</b> - print SPU commands as their received
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<li><b>cache</b> - print texture cache statistics when program exits
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</ul>
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<p>
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Note that some of these options may only work for linux-cell-debug builds.
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</p>
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<p>
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If the GALLIUM_NOPPC env var is set, PPC code generation will not be used
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and vertex shaders will be run with the TGSI interpreter.
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</p>
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<p>
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If the GALLIUM_NOCELL env var is set, the softpipe driver will be used
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intead of the Cell driver.
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This is useful for comparison/validation.
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</p>
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<H2>Contributing</H2>
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<p>
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If you're interested in contributing to the effort, familiarize yourself
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with the code, join the <a href="lists.html">mesa3d-dev mailing list</a>,
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and describe what you'd like to do.
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</p>
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</BODY>
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</HTML>
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