Bootlin contributions to Linux 5.11

Linux 5.11 was released quite some time ago now, but it’s never too late to have a look at Bootlin contributions to this release. As usual, we recommend reading the LWN articles on the 5.11 merge window: part 1 and part2. Also of interest is the Kernelnewbies page for 5.11.

Here are the main highlights of our contributions:

  • Alexandre Belloni, as the maintainer of the RTC subsystem, continued making numerous improvements and fixes to RTC drivers
  • On the support for Microchip ARM platforms, Alexandre Belloni switched the PWM atmel-tcb driver to a new Device Tree binding and added SAMA5D2 support, he did some improvements to the IIO driver for the Microchip ADC, and continued to remove platform_data support from Microchip drivers as all platforms are now converted to the Device Tree.
  • Alexandre Belloni contributed a new Simple Audio Mux driver for the ALSA subsystem, which can be used to control simple audio multiplexers driven using GPIOs, that allows to select which of their input line is connected to the output line.
  • Grégory Clement added support for several new MIPS platforms from Microchip: Luton, Serval and Jaguar2. All those platforms include a MIPS core, a few peripherals and more importantly an Ethernet switch. For now the support only includes the base platform support, but we are working on the switchdev driver for the Ethernet switch.
  • Miquèl Raynal, maintainer of the NAND subsystem and co-maintainer of the MTD subsystem, contributed numerous changes to the ECC support in the MTD subsystem, making it more generic so that it can be used not just for parallel NAND flashes, but also SPI NAND flashes. For more details, see the talk from Miquèl Raynal on this topic.

In addition to those 95 patches that we authored and contributed, several Bootlin engineers being maintainers of different subsystems of the Linux kernel reviewed and merged patches from other contributors:

  • Miquèl Raynal, as the NAND maintainer and MTD co-maintainer, reviewed and merged 67 patches from other contributors
  • Alexandre Belloni, as the RTC, I3C and Microchip ARM/MIPS platforms maintainer, reviewed and merged 47 patches from other contributors
  • Grégory Clement, as the Marvell EBU platform co-maintainer, reviewed and merged 33 patches from other contributors

Here is the detailed list of our contributions to Linux 5.11:

Videos and slides of Bootlin presentations at FOSDEM 2021

The videos from Bootlin’s presentations earlier this month at FOSDEM 2021 are now publicly available. Once again, FOSDEM was a busy event, even if it was online for once. As in most technical conferences, Bootlin engineers volunteered to share their experience and research by giving two talks.

Maxime Chevallier – Network Performance in the Linux Kernel, Getting the most out of the Hardware

Abstract: The networking stack is one of the most complex and optimized subsystems in the Linux kernel, and for a good reason. Between the wild range of applications, the complexity and variety of the networking hardware, getting good performance while keeping the stack easily usable from userspace has been a long-standing challenge.

Nowadays, complex Network Interface Controllers (NICs) can be found even on small embedded systems, bringing powerful features that were previously found only in the server world closest to day to day users.

This is a good opportunity to dive into the Linux Networking stack, to discover what is used to make networking as fast as possible, both by using all the features of the hardware and by implementing some clever software tricks.

In this talk, we cover these various techniques, ranging from simple batch processing with NAPI, queue management with RSS, RPS, XPS and so on, flow steering and filtering with ethool and TC, to finish with the newest big change that is XDP.

We dive into these various techniques and see how to configure them to squeeze the most out of your hardware, and discover that what was previously in the realm of datacenters and huge computers can now also be applied to embedded linux development.

Here are PDF slides for this presentation.

Michael Opdenacker – Embedded Linux from Scratch in 45 minutes, on RISC-V

Abstract: Discover how to build your own embedded Linux system completely from scratch. In this presentation and tutorial, we show how to build a custom toolchain (Buildroot), bootloader (opensbi / U-Boot) and kernel (Linux), that one can run on a system with the new RISV-V open Instruction Set Architecture emulated by QEMU. We also show how one can build a minimal root filesystem by oneself thanks to the BusyBox project. The presentation ends by showing how to control the system remotely through a tiny webserver. The approach is to provide only the files that are strictly necessary. That’s all the interest of embedded Linux: one can really control and understand everything that runs on the system, and see how simple the system can be. That’s much easier than trying to understand how a GNU/Linux system works from a distribution as complex as Debian!

The presentation also shares details about what’s specific to the RISC-V architecture, in particular about the various stages of the boot process. This presentation shares all the hardware (!), source code build instructions and demo binaries needed to reproduce everything at home, and add specific improvements. Most of the details are also useful to people using other hardware architectures (in particular arm and arm64).

It’s probably the first time a tutorial manages to show so many aspects of embedded Linux in less than an hour. See by yourself! At least, that’s for sure the first one demonstrating how to boot Linux from U-Boot in a RISC-V system emulated by QEMU.

Here are PDF slides for this presentation.

Bootlin acquired by Bootlin CTO Thomas Petazzoni and engineer Alexandre Belloni

We are happy to announce that Bootlin (formerly Free Electrons) has been acquired by two of its employees, Thomas Petazzoni and Alexandre Belloni.

Bootlin was founded in 2004 by Michael Opdenacker, with the goal of promoting the use of Linux and Free Software in embedded systems worldwide.

Thomas Petazzoni joined Bootlin in 2008, as the first employee. Thomas expanded the company offering by starting an engineering services activity, contributed to the growth of the company and took a CTO position. Thomas has a strong technical, open-source and embedded Linux background: he is the co-maintainer of the Buildroot project, has contributed to the Linux kernel, spoke at multiple international conferences and is the member of several embedded Linux conferences program committees. As Bootlin CTO, Thomas has been in charge of the complete engineering services activity: communication, sales, customer interaction, project management, scheduling and review.

Alexandre Belloni joined Bootlin in 2013, as an embedded Linux engineer. Alexandre has a deep open-source and technical background as well: he is the maintainer of multiple subsystems in the Linux kernel to which he has made significant contributions, and is an expert of the Yocto Project. He has been working closely with Thomas for many years in expanding and managing the engineering services activity.

As part of this acquisition, Thomas Petazzoni will become Bootlin’s CEO, while Alexandre Belloni will take the role of Bootlin’s COO. Michael Opdenacker will stay within Bootlin as an embedded Linux engineer and trainer.

“This acquisition is a logical continuation of my involvement in Bootlin and in the broader embedded Linux community” said Bootlin’s CEO Thomas Petazzoni, who added “I am proud to be leading the excellent engineering team at Bootlin, who will continue to offer the same training and engineering expertise to its customers worldwide”.

Alexandre Belloni, Bootlin’s COO, continued: “with two owners having both a strong technical background and a deep involvement in the open-source community, we intend to continue driving Bootlin with the same core values: technical excellence, open-source contribution and knowledge sharing”

Michael Opdenacker, Bootlin’s founder and former CEO, concluded: “Maria Llavata and I, after more than ten years of dedication to Bootlin’s customers and to the worldwide community of embedded Linux users and developers, are really happy to hand over the baton to Alexandre and Thomas, who have all the energy and enthusiasm needed to continue, expand and renew this beautiful adventure. I believe that Bootlin still has many new things to offer to the world, the fact that I am still on board is a proof of our trust in its new leadership.”

Device Tree 101 webinar slides and videos

As we announced back in January, we have offered in partnership with ST on February 9 a free webinar titled Device Tree 101, which gives a detailed introduction to the Device Tree, an important mechanism used in the embedded Linux ecosystem to describe hardware platforms. We were happy to see the interest around this topic and webinar.

Bootlin has always shared freely and openly all its technical contents, including our training materials, and this webinar is no exception. We are therefore sharing the slides and video recording of both sessions of this webinar:

Thanks to everyone who participated and thanks to ST for the support in organizing this event! Do not hesitate to share and/or like our video, and to suggest us other topics that would be useful to cover in future webinars!

New training course: embedded Linux boot time optimization

For many embedded products, the issue of how much time it takes from power-on to the application being fully usable by the end-user is an important challenge. Bootlin has been providing its expertise and experience in this area to its customers for many years through numerous boot time optimization projects, and we have shared this knowledge through a number of talks at several conferences over the past years.

We are now happy to announce that we have a new training course Embedded Linux boot time optimization, open for public registration. This training course was already given to selected Bootlin customers and is now available for everyone.

Embedded Linux boot time optimization

The training course will be lead by Michael Opdenacker, Bootlin’s founder, and author of several publications on the topic of boot time optimization. The course is organized over 4 sessions of 4 hours, with a significant fraction of time spent on practical demonstrations showing on a real-life example the techniques to measure and reduce the boot time of an embedded Linux system.

As usual with Bootlin, the training materials are fully available: Agenda, Slides and Practical lab instructions.

Boot time optimization slide

Our first course open for public registration will take place from April 6th to April 9th, 2021, from 14:00 to 18:00 UTC+2 (Paris time) on each day. The session cost is 519 EUR if you take advantage of the early bird price available until March 9th. Otherwise, the regular rate is 619 EUR. You can register now for this course on Eventbrite.

Also, if you’re interested in organizing a dedicated session for your company, do not hesitate to contact us.