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Chamelium Support in IGT
========================

This document provides information, instructions and a tasks list for Chamelium
support in IGT.

Introduction
------------

The Chamelium is a platform that acts as a display monitor emulator. It provides
advanced access and control over the various signals a display receives.

As such, it allows testing display features that can otherwise not be tested in
IGT without external hardware.

The platform was developed by Google in order to test display and audio-related
features of ChromeOS devices. It was initially developed internally by Google as
part of the ChromeOS effort under the name Chameleon and was later made external
as part of the ChromiumOS effort, under the name Chamelium.

It consists of a custom-made display emulator board connected to an Arrow SoCKit
via a flexible cable, with two DisplayPort connectors, one HDMI and one VGA.

The SoCKit uses a Cyclone V SoC, with both a FPGA and an ARM CPU. While the FPGA
is used for logic control, the CPU runs daemons that allow the board to be
controlled over the network via a XMLRPC interface.

Documentation
-------------

Documentation about the Chamelium is made available by Google through the
ChromiumOS projet wiki: https://www.chromium.org/chromium-os/testing/chamelium

Deploying the Chamelium With IGT
--------------------------------

Instructions from the ChromiumOS wiki detail how to setup the Chamelium:
https://www.chromium.org/chromium-os/testing/chamelium#TOC-Setting-up-Chamelium

The should be followed up until the "Setup your Linux host, DUT and the FPGA"
section. At this point, IGT has to be configured to connect to the Chamelium.

It may be necessary to give the Chamelium a static IP address, depending on
the network setup. This can be configured (via the serial console) by editing
the Debian-styled /etc/network/interfaces configuration file. Example setup:

    sudo screen /dev/ttyUSB0 115200
    sudo vi /etc/network/interfaces

and then configure eth0 like so:

    iface eth0 inet static
        address 192.168.1.2
        netmask 255.255.255.0
        gateway 192.168.1.1

This document supposes that target PC's network IP has "192.168.1.1/24" and
the Chamelium's network IP has "192.168.1.2/24".

Chamelium support requires setting up dedicated IGT configuration, as explained
in the Core and Chamelium parts of the IGT API Reference in the documentation.

Note that running the chamelium tests with the Chamelium configuration deployed
and the Chamelium disconnected or unreachable will result in network timeouts
that take seconds. It is thus preferable (especially in the case of an automated
CI system with a shared testlist) to remove the Chamelium configuration from the
hosts that shouldn't connect to the Chamelium so that they can be skipped, which
is faster than a network timeout.

It should also be noted that each Chamelium platform should only be used for
testing a single target device at a time. This is because the reset call issued
by the IGT tests is common to all connectors and thus one machine running a test
on a given connector may reset the Chamelium while another machine is running
a test on another connector.

IGT's behavior can be configured through a configuration file.
By default, this file is expected to exist in ~/.igtrc
In order to run tests using the Chamelium, a valid configuration file must be
present. It must contain Chamelium-specific keys as shown with the following
example (only Chamelium.URL is mandatory):

    # The common configuration section follows.
    [Common]
    # The path to dump frames that fail comparison checks
    FrameDumpPath=/root/

    # The following section is used for configuring the Device Under Test.
    # It is not mandatory and allows overriding default values.
    [DUT]
    SuspendResumeDelay=15

    [Chamelium]
    # The URL used for connecting to the Chamelium's RPC server
    URL=http://192.168.1.2:9992

    # The rest of the sections are used for defining connector mappings. This
    # is optional, the mappings will be discovered automatically.

    # The name of the DRM connector
    # The DP-1 of [Chamelium:DP-1] and the HDMI-A-1 of [Chamelium:HDMI-A-1] indicate
    # "connector info type" of /sys/kernel/debug/dri/0/i915_display_info.
    [Chamelium:DP-1]
    # The ChameliumPortID indicates physical port (device) id of a Chamelium Board.
    # A Chamelium daemon program defines these port ids as
    # DP1 (located next to the HDMI port) = 1
    # DP2 (located next to the VGA connector) = 2
    # HDMI = 3 and VGA = 4
    # The port ids are defined at:
    # https://chromium.googlesource.com/chromiumos/platform/chameleon/+/master/chameleond/utils/ids.py
    ChameliumPortID=1

    [Chamelium:HDMI-A-2]
    ChameliumPortID=3

    [Chamelium:VGA-1]
    ChameliumPortID=4

Running the Chamelium With IGT
------------------------------

$ ./scripts/run-tests.sh -t chamelium

Debugging the Chamelium
-----------------------

It is possible to manually send Chamelium RPC calls with the xmlrpc utility
(from xmlrpc-c). For instance, to plug the DisplayPort port:
$ xmlrpc http://192.168.1.2:9992 Plug i/1

The xmlrpc utility documentation is available at:
http://xmlrpc-c.sourceforge.net/doc/xmlrpc.html

The XML-RPC Chamelium interface is described here:
https://chromium.googlesource.com/chromiumos/platform/chameleon/+/refs/heads/master/chameleond/interface.py

Logs that may be useful for debugging can be obtained either by connecting to
the board via SSH or serial console and looking at the daemon logs from
/var/log, such as:
$ tail -f /var/log/chameleon*

Daemon Source, Build and Deploy
-------------------------------

Source code for the daemon running on the Chamelium is available at:
https://chromium.googlesource.com/chromiumos/platform/chameleon/

Building the daemon requires a GNU EABI ARMv7 GCC toolchain, that must be
specified via the CC variable, such as:
$ make CC=arm-linux-gnueabihf-gcc

The result can be deployed to the chamelium with the remote-install target and
specifying the network address for the chamelium via the CHAMELEON_HOST
variable, such as:
$ make remote-install CHAMELEON_HOST=192.168.72.1

The process requires the Chamelium to be connected to the Internet to succeed.

Audio Capture
-------------

The Chamelium supports audio capture. IGT tests take advantage of the
Chamelium streaming server to download audio samples from the Chamelium.

IGT needs direct access to audio devices through ALSA, so PulseAudio needs to
be stopped (otherwise audio tests will automatically get skipped). To make sure
PulseAudio isn't running:

- Edit /etc/pulse/client.conf and add autospawn=no
- Run `pulseaudio --kill` (if it succeeds, it means PulseAudio was running)
- Make sure a DE that automatically spawns PulseAudio isn't running

In case a test fails, the raw captured audio files will be dumped in a WAV
file.

Contributing Changes to the Daemon
----------------------------------

Contributions to the Chamelium daemon, just like any contribution to ChromiumOS,
are submitted and reviewed at: https://chromium-review.googlesource.com/

The ChromiumOS project provides an extensive developer guide:
https://chromium.googlesource.com/chromiumos/docs/+/master/developer_guide.md
It assumes running within the ChromiumOS build system. Since this is likely not
the case for contributing to the Chamelium daemon, only the part about
uploading changes is relevant:
https://chromium.googlesource.com/chromiumos/docs/+/master/developer_guide.md#Upload-your-changes-and-get-a-code-review

Most of the process is about using the Gerrit web interface for submitting and
having the change reviewed and not forgetting the Change-Id, TEST= and BUG=
fields in the commit.

Current Support in IGT
----------------------

Support for the Chamelium platform in IGT is found in the following places:
* lib/igt_chamelium.c: library with Chamelium-related helpers
* tests/kms_chamelium.c: sub-tests using the Chamelium

As of early April 2019, the following features are tested by IGT:
* Pixel-by-pixel frame integrity tests for DP and HDMI
* Error-trend-based frame integrity tests for VGA
* CRC-based frame integrity tests for DP and HDMI
* Hotplug event simple tests for all interfaces
* Hotplug event stressing tests, emulating a flaky cable for DisplayPort and
  HDMI
* Hotplug event during suspend test for all interfaces, either separately for
  each interface or combined
* EDID display identifier integrity check for all interfaces
* EDID display identifier change during suspend for all interfaces
* Audio Fourier-based tests for DP at 48KHz

Future Developments
-------------------

With the current generation of the hardware platform, support for testing a
number of additional display features could be included as future developments,
including:
* Audio capture from HDMI
* Check all channels are independent from each other
* Playback using more than 2 channels, different sampling rates and different
  sample sizes
* High-bandwidth Digital Content Protection (HDCP) streaming to the display
* Remote control forwarding (CEC) sent from the display
* YUV colorspace for HDMI, instead of RGB
* Partial testing of DP Multi-Stream Transport (MST) using an external MST hub
  and the two available DP connectors of the platform

While HDCP is already supported by the Chamelium daemon, features such as CEC
and YUV are not and must be implemented there before any support for them can
be added to IGT. Audio is supported by the Chamelium daemon for HDMI only and
a way to retrieve the captured data via the XMLRPC interface needs to be added
to the daemon.