Introduction
Project Etnaviv is an open source user-space driver for the Vivante GCxxx series of embedded GPUs.
A Mesa fork with the etnaviv driver can be found in the laanwj/mesa repository. At the moment, this driver provides OpenGL ES 1.0 and 2.0 accelerated rendering direct to framebuffer (fbdev). This driver has been used to run Dark Places, glquake, d2x and other GLES games so it should be fairly stable. There may still be a few rendering bugs, specific bug reports are very welcome. Be sure to attach apitrace logs if possible.
SoCs with Vivante GPU
ARM-based:
- Marvell Armada 1500 has a GC1000: Google TV, OLPC XO-4
- Marvell Armada 610 has a GC860: OLPC XO-1.75
- Marvell Armada 510 has a GC600: CuBox
- Rockchip 2918 has a GC800: some Arnova tablets
- Freescale i.MX6 Quad and Dual have a GC2000 + GC320 + GC355
- Freescale i.MX6 DualLite and Solo have a GC880 + GC320
- Freescale i.MX6 SoloLite has GC320 + GC355 (no 3D)
- Actions Semiconductor ATM7029 has a GC1000
MIPS-based:
- Ingenic JZ4760 has a GC200 (2D only)
- Ingenic JZ4770 has a GC860: GCW Zero
See also wikipedia.
For the Vivante GPUs on many platforms feature bits have been determined, these can be found in doc/gpus_comparison.html.
Compatibility
etna_pipe
is currently compatible with at least the following GC chips:
- GC600 (CuBox, GCABI
dove
) - GC800 (Rockchip, GCABI
arnova
) - GC860 (GCW Zero, GCABI
v2
) - GC880 (i.MX6, GCABI imx6 or
imx6_v4_0_0
depending on BSP) - GC1000
Support for GC2000 (i.MX6) and others with multiple pixel pipes (GC4000?) requires a few changes. The 2D demos do work for GC2000 and should work on all other known Vivante chips.
Building
As we currently use whatever Vivante kernel driver is available, the build process is complicated by
the existence of many different kernel drivers, with their subtly different interface (different
headers, different offsets for fields, different management of context, and so on). These values
for environment variable GCABI
are supported out of the box:
dove
: Marvell Dove, newer drivers (0.8.0.3184)dove_old
: Marvell Dove, older drivers (0.8.0.1998, 0.8.0.1123)arnova
: Android, Arnova 10B G3 tablet (RK2918)v2
: Variousv4
: Various, newer API than v2v4_uapi
: Likev4
but condensed into one header without all the unnecessary crap and renamed fields not used by the kernel (user space interface of the https://github.com/gcwnow/linux/tree/jz-3.11/drivers/gpu/vivante/v4 condensed kernel version)imx6
: v4 API, specialized for i.MX6, pre-4.0.0 releaseimx6_v4_0_0
: v4 API, but i.MX6 specific, release 4.0.0imx6_v4_1_0
: v4 API, but i.MX6 specific, release 4.1.0
If possible get the gc_*.h
headers for your specific kernel version. If that's not possible, try
to find which of the above sets of headers is most similar, and use or adapt that.
General
If the goal is to build Mesa and you are not planning to do reverse engineering, only libetnaviv.a
needs to be built.
In this case it is sufficient to run make in src/etnaviv
.
Otherwise, run make
and make rev
in src/
(see the README.md in src
for a description of all the directories contained within).
gc_abi.h
gc_abi.h
is an extra header that defines the following flags describing the kernel interface to etna, for a certain
setting of the environment variable GCABI
:
GCABI_CONTEXT_HAS_PHYSICAL
:struct _gcoCONTEXT
hasphysical
andbytes
fieldsGCABI_HAS_MINOR_FEATURES_2
:struct _gcsHAL_QUERY_CHIP_IDENTITY
haschipMinorFeatures2
fieldGCABI_HAS_MINOR_FEATURES_3
:struct _gcsHAL_QUERY_CHIP_IDENTITY
haschipMinorFeatures3
fieldGCABI_USER_SIGNAL_HAS_TYPE
:struct _gcsHAL_USER_SIGNAL
hassignalType
fieldGCABI_HAS_CONTEXT
:struct _gcsHAL_COMMIT
hascontextBuffer
fieldGCABI_HAS_STATE_DELTAS
:struct _gcsHAL_COMMIT
hasdelta
field
Linux cross compile
For non-Android Linux ARM cross compile, create a script like this (example for CuBox) to set up the build environment.
When command stream dumping the egl demos, don't forget to also copy the EGL/GLES2/KDR headers from
some place and put them in a directory include
under the location
where the script is installed, and get the libEGL.so
and libGLESv2.so
from the device into lib
:
DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
export GCCPREFIX="arm-linux-gnueabi-"
export PLATFORM_CFLAGS="-I${DIR}/include"
export PLATFORM_CXXFLAGS="-I${DIR}/include"
export PLATFORM_LDFLAGS="-ldl -L${DIR}/lib"
# These point to the vivante libs that are only used for reverse engineering
export PLATFORM_GL_LIBS="-lEGL -lGLESv2 -L${TOP}/lib/egl -Xlinker --allow-shlib-undefined"
# Set GC kernel ABI to dove (important!)
#export GCABI="dove" # 0.8.0.3184
export GCABI="dove_old" # 0.8.0.1998, 0.8.0.1123
If you haven't got the arm-linux-gnueabi-
bintools, on an Debian/Ubuntu host they can be installed with
apt-get install gcc-arm-linux-gnueabi g++-arm-linux-gnueabi
On ARM hardfloat targets you should use gcc-arm-linux-gnueabihf-
instead.
Android cross compile
To build for an Android device, install the Android NDK and define the cross-build environment by setting environment variables, for example like this:
export NDK="/opt/ndk"
export TOOLCHAIN="/opt/ndk/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86"
export SYSROOT="/opt/ndk/platforms/android-14/arch-arm"
export PATH="$PATH:$TOOLCHAIN/bin"
export GCCPREFIX="arm-linux-androideabi-"
export CXXABI="armeabi-v7a"
export PLATFORM_CFLAGS="--sysroot=${SYSROOT} -DANDROID -DPIPE_ARCH_LITTLE_ENDIAN"
export PLATFORM_CXXFLAGS="--sysroot=${SYSROOT} -DANDROID -DPIPE_ARCH_LITTLE_ENDIAN -I${NDK}/sources/cxx-stl/gnu-libstdc++/4.6/include -I${NDK}/sources/cxx-stl/gnu-libstdc++/4.6/libs/${CXXABI}/include"
export PLATFORM_LDFLAGS="--sysroot=${SYSROOT} -L${NDK}/sources/cxx-stl/gnu-libstdc++/4.6/libs/${CXXABI} -lgnustl_static"
# Set GC kernel ABI (important!)
#export GCABI="v2"
#export GCABI="v4"
export GCABI="arnova"
To build the egl samples (for command stream interception), you need to copy libEGL_VIVANTE.so
libGLESv2_VIVANTE.so
from
the device /system/lib/egl
to src/lib/egl
. This is not needed if you just want to build the replay
, etna
or fb
tests, which do not rely in any way on the userspace blob.
Contents
The repository contains various tools and documentation related to figuring out how to program Vivante GCxxx GPU cores.
Framebuffer tests
To exercise the gallium driver there are a few framebuffer tests in src/fb
.
These demos do double-buffered animated rendering of 1000 frames to the framebuffer using
the proof-of-concept etna
rendering and command stream building API. The goal of this API is to provide a Gallium-like
low-level interface to the Vivante hardware while abstracting away kernel interface details.
-
companion_cube
: Rotating "weighted companion cube", using array or indexed rendering. Exercised in this demo:- Array and indexed rendering of arbitrary mesh
- Video memory allocation
- Setting up render state
- Depth buffer
- Vertex / fragment shader
- Texturing
- Double-buffered rendering to framebuffer
- MSAA (off / 2X / 4X)
-
mip_cube_state
: Rotating cube with a mipmapped texture loaded from adds
file provided on the command line. One of the example textures have a different color and number on each mipmap level, to explicitly show interpolation between mipmap levels as the surface goes nearer or farther from the camera.- Mipmapping
- DXT1 / DXT3 / DXT5 / ETC1 compressed textures
-
alpha_blend
: Alpha blending quads -
cubemap_sphere
: Cubemap textures -
stencil_test
: Test stencil buffer handling -
particle_system
: Simple particle system using vertex shader and point sprites -
displacement
: Displacement mapping using vertex texture fetch
If you are executing these demos on an Android device, make sure that you are root, otherwise the framebuffer is not accessible.
Running these tests while Android is still writing to the framebuffer will result in stroboscopic effects. To get surfaceflinger out of the way type:
adb shell stop surfaceflinger
(run test)
adb shell start surfaceflinger
libetnaviv
Low-level command buffer handling library and register definition headers. This library completely wraps the kernel interface, to isolate clients (such as Mesa) from the madness of kernel-specific headers and defines.
- ioctl (kernel interface) wrapping
- video memory management
- command buffer and event queue handling
- context / state delta handling (still incomplete)
- register description headers
- converting surfaces and textures from and to Vivante specific tiling formats
Currently used only by the 3D driver in src/driver
. A future 2D, SVG or OpenCL driver can share this code.
Debugging support
Etnaviv comes with a GDB plugin for etna
driver debugging. GDB 7.5+ with Python support (usually enabled
by default in distributions) is needed for it to work. This plugin adds a few custom commands.
Usage (from gdb):
source /path/to/etnaviv_gdb.py
Commands:
-
gpu-state [<prefix>] gpu-state uniforms
Show full GPU state by default or a subset of the registers with a certain prefix. The special prefix 'uniforms' shows the shader uniforms.
-
gpu-dis
Disassemble the currently bound fragment and vertex shaders.
-
gpu-trace
Trace and dump all submitted command buffers. This is similar to dumping to FDR (using one of the hook mechanisms) and then running
dump_cmdstream
, however this works on the fly.Along with each command the physical address is printed, this should come in handy for searching back the physical address that the GPU is stuck on according to the kernel.
Usage: gpu-trace <on|off> Enable/disable cmdbuffer trace gpu-trace stop <on|off> Enable/disable stopping on every commit gpu-trace output stdout Set tracing output to stdout (default) gpu-trace output file Set tracing output to file
These commands automatically find the gallium pipe and screen from the current Mesa context.
State map
Map of documentation for known render state and registers. Mapped in rules-ng-ng (envytools) format:
rnndb/state.xml Top-level database, global state
rnndb/state_hi.xml Host interface registers
rnndb/state_2d.xml 2D engine state
rnndb/state_3d.xml 3D engine state
rnndb/state_common.xml Common, shared state defines
Other scattered bits of documentation about the hardware and ISA can be found in doc/hardware.md
.
ISA documentation
Vivante has a unified, fixed-size, predictable instruction format with explicit inputs and outputs. This does simplify code generation, compared to a weird flow pipe system like the Mali 200/400. Shader (both vertex and fragment) instruction set description in rules-ng-ng format can be found here:
rnndb/isa.xml
Some written down notes, and examples of disassembled shaders can be found here:
doc/isa.md
Assembler and disassembler
A basic disassembler for the shader instructions (to a custom format) can be found in the tools directory:
tools/disasm.py <shader.bin>
This can be used to disassemble shaders extracted using dump_cmdstream.py --dump-shaders
.
There is also an assembler, which accepts the same syntax that is produced by the disassembler:
tools/asm.py <shader.asm> [-o <shader.bin>]
Command stream format
Like other modern GPUs, the primary means of programming the chip is through a command stream interpreted by a DMA engine. This "Front End" takes care of distributing state changes through the individual modules of the GPU, kicking off primitive rendering, synchronization, and also supports basic flow control (branch, call, return).
Most of the relevant bits of this command stream have been deciphered.
The command stream format represented in rules-ng-ng XML format can be found here:
rnndb/cmdstream.xml
Command stream interception
A significant part of reverse engineering was done by intercepting command streams while running GL simple demos.
viv_hook
is a library to intercept and log the traffic between libGAL
(the Vivante user space blob) and the kernel
driver / hardware.
This library uses ELF hooks to intercept only system calls such as ioctl
and mmap
coming from the driver, not from
other parts of the application, unlike more crude hacks using LD_PRELOAD
.
At the beginning of the program call the_hook
, at the end of the program call end_hook
to finalize
and flush buffers. This should even work for native android applications that fork from the zygote.
The raw binary structures interchanged with the kernel are written to disk in a .fdr
file, along
with updates to video memory, to be parsed by the accompanying command stream dumper and other tools.
Command stream dumper
Other tools live in:
tools/
The most useful ones, aside from the assembler and disassembler mentioned before are:
show_egl2_log.sh
(usesdump_cmdstream.py
, you may have to adapt this script to use another structure definition JSON depending on your kernel interface)
Decodes and dumps the intercepted command stream in human readable format, making use of rnndb state maps.
fdr_dump_mem.py
Extract areas of video memory, images, and command buffers at certain points of execution.
Replay tests
The replay tests replay the command stream and ioctl commands of the EGL demos, to get the same output.
They can be found in src/replay
.
Currently this is available for the cube
example that renders a smoothed cube, and the cube_companion
example that renders a textured cube.
Vivante GPL kernel drivers
The headers and implementation files for the Vivante GPL kernel drivers are also included:
kernel_drivers/
Four GPL kernel driver versions, gc600_driver_dove
, v2
and v4
and imx6
, are provided. They are useful in understanding the kernel
interface, and the hardware at a basic level.
As open source drivers for the kernel are available, there are currently no plans to write a DRM/DRI kernel driver for Vivante. (There may be other reasons to do this anyway, you're welcome to contribute one)
Envytools fork
Envytools is a set of tools aimed at developers of the open source NVIDIA driver Nouveau, however some parts such as rnndb can be applied more generally. The repository contains a slightly modified subset of envytools for header generation from the state / command stream / ISA rnndb files, so they can be used from the C code (etna), build with
cd envytools
mkdir build
cd build
cmake ..
make
cd ../..
Then generate the headers with
rnndb/gen_headers.sh
Contact
There is currently no mailing list for this project, and looking at other GPU reverse engineering projects the mailing lists usually see very little traffic, so I won't bother (but you're free to create one and let me know so I can join).
We usually hang out in #etnaviv
on irc.freenode.net
.
Authors
- Wladimir J. van der Laan
- Steven J. Hill (kernel driver help)
- Christian Gmeiner (beginnings of GC2000 support)
- Michał Ściubidło (GC880 support)
- Maarten ter Huurne (GCW kernel driver,
v4_uapi
interface)
Thanks
- Luc Verhaegen (libv) of Lima project (basic framework, general idea)
- Nouveau developers (rnndb, envytools)