# Linux driver stack for Arm(R) Ethos(TM)-U

The Linux driver stack for Arm(R) Ethos(TM)-U provides an example of how a rich
operating system like Linux can dispatch inferences to an Arm Cortex(R)-M
subsystem, consisting of an Arm Cortex-M of choice and an Arm Ethos-U NPU.

## Building

The driver stack comes with a CMake based build system. Cross compile for an Arm
CPU can for example be done with the provided toolchain file.

```
$ mkdir build
$ cd build
$ cmake .. -DCMAKE_TOOLCHAIN_FILE=../cmake/toolchain/aarch64-linux-gnu.cmake -DKDIR=<Kernel directory>
$ make
```

## DTB

The kernel driver uses the mailbox APIs as a doorbell mechanism.

```
/ {
  reserved-memory {
    #address-cells = <2>;
    #size-cells = <2>;
    ranges;

    ethosu_msg: ethosu_msg@80000000 {
      compatible = "shared-dma-pool";
      reg = <0 0x80000000 0 0x00040000>;
      no-map;
    };

    ethosu_reserved: ethosu_reserved@80040000 {
      compatible = "shared-dma-pool";
      reg = <0 0x80040000 0 0x00040000>;
      no-map;
    };
  };

  ethosu_mailbox: mhu@6ca00000 {
    compatible = "arm,mhu", "arm,primecell";
    reg = <0x0 0x6ca00000 0x0 0x1000>;
    interrupts = <0 168 4>;
    interrupt-names = "npu_rx";
    #mbox-cells = <1>;
    clocks = <&soc_refclk100mhz>;
    clock-names = "apb_pclk";
  };

  ethosu {
    #address-cells = <2>;
    #size-cells = <2>;

    compatible = "arm,ethosu";
    reg = <0 0x80000000 0 0x00010000>,
          <0 0x80010000 0 0x00010000>;
    reg-names = "in_queue", "out_queue";
    memory-region = <&ethosu_reserved>;
    dma-ranges = <0 0x60000000 0 0x80000000 0 0x20000000>;
    mboxes= <&ethosu_mailbox 0>, <&ethosu_mailbox 0>;
    mbox-names = "tx", "rx";
  };
};
```

# Licenses

The kernel drivers are provided under a GPL v2 license. All other software
componantes are provided under an Apache 2.0 license.

Please see [LICENSE-APACHE-2.0.txt](LICENSE-APACHE-2.0.txt) and
[LICENSE-GPL-2.0.txt](LICENSE-GPL-2.0.txt) for more information.

# Contributions

The Arm Ethos-U project welcomes contributions under the Apache-2.0 license.

Before we can accept your contribution, you need to certify its origin and give
us your permission. For this process we use the Developer Certificate of Origin
(DCO) V1.1 (https://developercertificate.org).

To indicate that you agree to the terms of the DCO, you "sign off" your
contribution by adding a line with your name and e-mail address to every git
commit message. You must use your real name, no pseudonyms or anonymous
contributions are accepted. If there are more than one contributor, everyone
adds their name and e-mail to the commit message.

```
Author: John Doe \<john.doe@example.org\>
Date:   Mon Feb 29 12:12:12 2016 +0000

Title of the commit

Short description of the change.
   
Signed-off-by: John Doe john.doe@example.org
Signed-off-by: Foo Bar foo.bar@example.org
```

The contributions will be code reviewed by Arm before they can be accepted into
the repository.

# Security

Please see [Security](SECURITY.md).

# Trademark notice

Arm, Cortex and Ethos are registered trademarks of Arm Limited (or its
subsidiaries) in the US and/or elsewhere.