8248cc0bf4
The front-page of the docs is currently fairly intimidating, by diving into details rather abruptly. Let's try to make it a bit easier to navigate t by moving the details to their own articles, but linking them from the front-page. Acked-by: Daniel Stone <daniels@collabora.com> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28953>
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85 lines
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drm-shim
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========
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Panfrost implements ``drm-shim``, stubbing out the Panfrost kernel interface.
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Use cases for this functionality include:
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- Future hardware bring up
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- Running shader-db on non-Mali workstations
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- Reproducing compiler (and some driver) bugs without Mali hardware
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Although Mali hardware is usually paired with an Arm CPU, Panfrost is portable C
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code and should work on any Linux machine. In particular, you can test the
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compiler on shader-db on an Intel desktop.
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To build Mesa with Panfrost drm-shim, configure Meson with
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``-Dgallium-drivers=panfrost`` and ``-Dtools=drm-shim``. See the above
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building section for a full invocation. The drm-shim binary will be built to
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``build/src/panfrost/drm-shim/libpanfrost_noop_drm_shim.so``.
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To use, set the ``LD_PRELOAD`` environment variable to the drm-shim binary. It
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may also be necessary to set ``LIBGL_DRIVERS_PATH`` to the location where Mesa
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was installed.
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By default, drm-shim mocks a Mali-G52 system. To select a specific Mali GPU,
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set the ``PAN_GPU_ID`` environment variable to the desired GPU ID:
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========= ============= =======
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Product Architecture GPU ID
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========= ============= =======
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Mali-T720 Midgard (v4) 720
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Mali-T860 Midgard (v5) 860
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Mali-G72 Bifrost (v6) 6221
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Mali-G52 Bifrost (v7) 7212
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Mali-G57 Valhall (v9) 9093
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Mali-G610 Valhall (v10) a867
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========= ============= =======
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Additional GPU IDs are enumerated in the ``panfrost_model_list`` list in
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``src/panfrost/lib/pan_props.c``.
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As an example: assuming Mesa is installed to a local path ``~/lib`` and Mesa's
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build directory is ``~/mesa/build``, a shader can be compiled for Mali-G52 as:
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.. code-block:: sh
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~/shader-db$ BIFROST_MESA_DEBUG=shaders \
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LIBGL_DRIVERS_PATH=~/lib/dri/ \
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LD_PRELOAD=~/mesa/build/src/panfrost/drm-shim/libpanfrost_noop_drm_shim.so \
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PAN_GPU_ID=7212 \
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./run shaders/glmark/1-1.shader_test
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The same shader can be compiled for Mali-T720 as:
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.. code-block:: sh
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~/shader-db$ MIDGARD_MESA_DEBUG=shaders \
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LIBGL_DRIVERS_PATH=~/lib/dri/ \
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LD_PRELOAD=~/mesa/build/src/panfrost/drm-shim/libpanfrost_noop_drm_shim.so \
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PAN_GPU_ID=720 \
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./run shaders/glmark/1-1.shader_test
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These examples set the compilers' ``shaders`` debug flags to dump the optimized
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NIR, backend IR after instruction selection, backend IR after register
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allocation and scheduling, and a disassembly of the final compiled binary.
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As another example, this invocation runs a single dEQP test "on" Mali-G52,
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pretty-printing GPU data structures and disassembling all shaders
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(``PAN_MESA_DEBUG=trace``) as well as dumping raw GPU memory
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(``PAN_MESA_DEBUG=dump``). The ``EGL_PLATFORM=surfaceless`` environment variable
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and various flags to dEQP mimic the surfaceless environment that our
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continuous integration (CI) uses. This eliminates window system dependencies,
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although it requires a specially built CTS:
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.. code-block:: sh
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~/VK-GL-CTS/build/external/openglcts/modules$ PAN_MESA_DEBUG=trace,dump \
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LIBGL_DRIVERS_PATH=~/lib/dri/ \
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LD_PRELOAD=~/mesa/build/src/panfrost/drm-shim/libpanfrost_noop_drm_shim.so \
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PAN_GPU_ID=7212 EGL_PLATFORM=surfaceless \
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./glcts --deqp-surface-type=pbuffer \
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--deqp-gl-config-name=rgba8888d24s8ms0 --deqp-surface-width=256 \
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--deqp-surface-height=256 -n \
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dEQP-GLES31.functional.shaders.builtin_functions.common.abs.float_highp_compute
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