Thursday, March 28, 2024

Rockchip NPU update 2: MobileNetV1 is done


For  the last couple of weeks I have kept chipping at a new userspace driver for the NPU in the Rockchip RK3588 SoC.

I am very happy to report that the work has gone really smooth and I reached my first milestone: running the MobileNetV1 model with all convolutions accelerated by the NPU.

And it not only runs flawlessly, but at the same performance level as the blob.

It has been great having access to the register list as disclosed by Rockchip in their TRM, and to the NVDLA and ONNC documentation and source code. This has allowed for the work to proceed at a pace several times faster than with my previous driver for the VeriSilicon NPU, for which a lot of painstaking reverse engineering had to be done.

by Julien Langlois CC BY-SA 3.0

 tomeu@arm-64:~/mesa$ TEFLON_DEBUG=verbose python3.10 -i hens.jpg -m mobilenet_v1_1.0_224_quant.tflite -l labels_mobilenet_quant_v1_224.txt -e
Loading external delegate from with args: {}
Teflon delegate: loaded rknpu driver

teflon: compiling graph: 89 tensors 27 operations
teflon: compiled graph, took 413 ms
teflon: invoked graph, took 11 ms
teflon: invoked graph, took 11 ms
teflon: invoked graph, took 11 ms
teflon: invoked graph, took 10 ms
teflon: invoked graph, took 10 ms
0.984314: hen
0.019608: cock
0.000000: toilet tissue
0.000000: sea cucumber
0.000000: wood rabbit
time: 10.776ms

Notice how nothing in the invocation refers to the specific driver that TensorFlow Lite is using, that is completely abstracted by Mesa. Once all these bits are upstream and packaged by distros, one will be able to just download a model in INT8 quantization format and get accelerated inferences going fast irrespective of the hardware.

Thanks to TL Lim of PINE64 for sending me a QuartzPro64 board for me to hack on.

Next steps

I want to go back and get my last work on performance for the VeriSilicon driver upstreamed, so it is packaged in distros sooner rather than later.

After that, I'm a bit torned between working further on the userspace driver and implementing more operations and control flow, or start writing a kernel driver for mainline.

Saturday, March 16, 2024

Rockchip NPU update 1: A walk in the park?

During the past weeks I have paused work on the driver for the Vivante NPU and have started work on a new driver, for Rockchip's own NPU IP, as used in SoCs such as RK3588(S) and RK3568.

The version of the NPU in the RK3588 claims a performance of 6 TOPS across its 3 cores, though from what I have read, people are having trouble making use of more than one core in parallel, with the closed source driver.

A nice walk in the park

Rockchip, as most other vendors of NPU IP, provides a GPLed kernel driver and pushes out their userspace driver in binary form. The kernel driver is pleasantly simple and relatively up-to-date in regards of its use of internal kernel APIs. The userspace stack though is notoriously buggy and difficult to use, with basic features still unimplemented and performance being quite below what the hardware should be able to achieve.

To be clear, this is on top of the usual problems related to closed-source drivers. I get the impression that Rockchip's NPU team is really understaffed.

Other people had already looked at reverse-engineering the HW so they could address the limitations and bugs in the closed source driver, and use it in situations not supported by Rockchip. I used information acquired by Pierre-Hugues Husson and Jasbir Matharu to get started, a big thanks to them!

After the initial environment was setup (had to forward-port their kernel driver to v6.8), I wrote a simple library that can be loaded in the process with LD_PRELOAD and that, by overriding the ioctl and other syscalls, I was able to dump the buffers that the proprietary userspace driver sends to the hardware.

I started looking at a buffer that from the debug logs of the proprietary driver contained register writes, and when looking at the register descriptions in the TRM, I saw that it had to be closely based on NVIDIA's NVDLA open-source NPU IP.

With Rockchip's (terse) description of the registers, NVDLA's documentation and source code for both the hardware and the userspace driver, I have been able to make progress several times faster than I was able to when working on VeriSilicon's driver (for which I had zero documentation).

Right now I am at the stage at which I am able to correctly execute TensorFLow Lite's Conv2D and DepthwiseConv2D operations with different combinations of input dimensions, weight dimensions, strides and padding. Next is to support multiple output channels.

I'm currently using Rockchip's kernel, but as soon as I'm able to run object detection models with decent hardware utilization, I plan to start writing a new kernel driver for mainlining.

Rockchip's kernel driver has gems such as passing addresses in the kernel address space across the UAPI...

Tests run fast and reliably, even with high concurrency:

tomeu@arm-64:~/mesa$ TEFLON_TEST_DELEGATE=~/mesa/build/src/gallium/targets/teflon/ TEFLON_TEST_DATA=src/gallium/targets/teflon/tests LD_LIBRARY_PATH=/home/tomeu/tflite-vx-delegate/build/_deps/tensorflow-build/ ~/.cargo/bin/gtest-runner run --gtest /home/tomeu/mesa/build/src/gallium/targets/teflon/test_teflon --output /tmp -j8 --tests-per-group 1 --baseline ~/mesa/src/gallium/drivers/rocket/ci/rocket-rk3588-fails.txt --flakes ~/mesa/src/gallium/drivers/rocket/ci/rocket-rk3588-flakes.txt  --skips ~/mesa/src/gallium/drivers/rocket/ci/rocket-rk3588-skips.txt
Running gtest on 8 threads in 1-test groups
Pass: 0, Duration: 0
Pass: 139, Skip: 14, Duration: 2, Remaining: 2
Pass: 277, Skip: 22, Duration: 4, Remaining: 0
Pass: 316, Skip: 24, Duration: 4, Remaining: 0

You can find the source code in this branch.