Arista platform support for SONiC

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.

License

All linux kernel code is licensed under the GPLv2. All other code is licensed under the GPLv3. Please see the LICENSE file for copies of both licenses.

Purpose

This package provides open source hardware support for Arista devices. It is mainly targeted at SONiC OS (debian based) but should work on any system. For more details visit the SONiC website

In normal operations, the platform is initialized at boot time via a set of systemd services. These services run commands using the arista tool.

This tool detects on which platform it is running before loading the appropriate kernel drivers. Once the initialization is complete, the system exposes various components through the sysfs such as fans, leds, xcvrs, ...

Supported platforms

The following platforms are currently supported,

DCS-7050QX-32
DCS-7050QX-32S
DCS-7050CX3-32S
DCS-7060CX-32
DCS-7060CX2-32
DCS-7060PX4-32 and DCS-7060DX4-32
DCS-7170-32C
DCS-7170-32CD
DCS-7170-64C
DCS-7260CX3-64
DCS-7280CR3-32P4 and DCS-7280CR3-32D4

Some variants were omitted but might be supported see arista platforms for a detailed list of supported SKUs.

Some platforms might require custom kernel patches and configs. A working configuration is maintained under the SONiC kernel repository.

Packaging

The current debian packaging mechanism creates 4 packages.

sonic-platform-arista : system configuration files
drivers-sonic-platform-arista : kernel modules and drivers
python2-sonic-platform-arista : python2 library to manage the hardware
python3-sonic-platform-arista : python3 library to manage the hardware

Usage

At boot time the systemd services under systemd/ are loaded. When runnable they will perform the platform initialization.

The central piece of the platform support is the arista entry point. It is a python script that load the arista platform library to perform actions. This library is python2/python3 compatible.

For more details on the available commands see the help message

arista --help

The arista python library also possess other entry points for APIs. SONiC uses a few like sonic_platform, sfputil, sonic_eeprom, ...

Drivers

The kernel drivers in this repository are mostly running on a 4.9 kernel. They are also compatible with 4.19 and potentially higher kernel versions.

scd-hwmon

The scd-hwmon is the current implementation for the scd and is being used on all platforms.

When the scd-hwmon driver is loaded, the various gpios and resets can be set and unset by writing into the sysfs file. The meaning of 0 or 1 should be deduced based on the name of the sysfs entry.

cd /sys/module/scd/drivers/pci:scd/<pciAddr>/
# put the switch chip in reset
echo 1 > switch_chip_reset

Components

This section describes how to interact with the various components exposed by the kernel drivers. In order to see them, the platform must be successfully initialized.

The following sections describe how to manually interact with the components. Examples shown may differ across platforms but the logic stays the same.

LEDs

LED objects can be found under /sys/class/leds.The brightness field is used to toggle between off and different colors. The brightness to LED color mapping is as follows (0 maps to off for all LEDs):

status, fan_status, psu1, psu2:
  0 => off
  1 => green
  2 => red

beacon:
  1+ => blue

qsfp:
  1 => green
  2 => yellow

fan:
  1 => green
  2 => red
  3 => yellow

Given that this repository is primarily aimed at running on SONiC, an implementation of the led_control plugin is available under arista.utils.sonic_leds. It requires access to the port_config.ini file to translate from interface name to front panel port.

Fans

Fans are exposed under /sys/class/hwmon/* and respect the sysfs-interface guidelines.

This repository provides the kernel modules to handle the fans.

Temperature sensors

Temperature sensors are exposed under /sys/class/hwmon/* and also respect the sysfs-interface.

They are all managed by linux standard modules like lm73 and max6658.

Power supplies

Power supplies and power controllers can be managed by the kernel's generic pmbus module. Assuming the pmbus module was compiled into the kernel.

Some power supplies may need kernel patches against the pmbus driver.

System EEPROM

The system eeprom contains platform specific information like the SKU, the serial number and the base mac address.

The location of the eeprom that contains this information vary from one product to another. The most reliable way to get this information is to run arista syseeprom

The library implements the SONiC eeprom plugin under arista.utils.sonic_eeprom.

Transceivers - QSFPs / SFPs

Currently only platforms with QSFP+, SFP+, OSFP and QSFPDD ports are supported. All transceivers provide 2 kinds of information.

Pins

The first piece of information is obtained from the transceiver physical pins.

OSFP: present, reset, low power mode, interrupt, module select
QSFP: present, reset, low power mode, interrupt, module select
SFP: present, rxlos, txfault, txdisable

These knobs are accessible under /sys/module/scd/drivers/pci:scd/.../ The name of the entries follow this naming <type><id>_<pin> For example qsfp2_reset or sfp66_txdisable.

See this section on how to use them.

Eeproms

The second piece of information provided by a transceiver is the content of its eeprom. It is accessible via SMBus at the fixed address 0x50. Some transceivers also exist at other SMBus addresses like 0x51 and 0x56.

On linux, an unoffical module called optoe manages such devices. This library implements the spfutil plugin for SONiC to manage xcvrs.

Before being read, the QSFP+, OSFP and QSFPDD modules must be taken out of reset and have their module select signals asserted. This can be done through the GPIO interface. The library does it at boot time.

QSFP - SFP multiplexing

On the DCS-7050QX-32S, the first QSFP port and the 4 SFP ports are multiplexed. To choose between one or the other, write into the sysfs file located under /sys/modules/scd/drivers/pci:scd/.../mux_sfp_qsfp

GPIOs and resets

Most of the GPIOs of the system are exposed by the scd-hwmon driver. They should be available under /sys/module/scd/drivers/pci:scd/.../.

nick-bsn / sonic