Bootlin at FOSDEM and the Buildroot Developers Meeting

FOSDEM 2016The FOSDEM conference will take place on January 30-31 in Brussels, Belgium. Like every year, there are lots of interesting talks for embedded developers, starting from the Embedded, Mobile and Automotive Devroom, but also the Hardware track, the Graphics track. Some talks of the IoT and Security devrooms may also be interesting to embedded developers.

Thomas Petazzoni, embedded Linux engineer and CTO at Bootlin, will be present during the FOSDEM conference. Thomas will also participate to the Buildroot Developers Meeting that will take place on February 1-2 in Brussels, hosted by Google.

Linux 4.4, Bootlin contributions

Linux 4.4 is the latest releaseLinux 4.4 has been released, a week later than the normal schedule in order to allow kernel developers to recover from the Christmas/New Year period. As usual, LWN has covered the 4.4 cycle merge window, in two articles: part 1 and part 2. This time around, KernelNewbies has a nice overview of the Linux 4.4 changes. With 112 patches merged, we are the 20th contributing company by number of patches according to the statistics.

Besides our contributions in terms of patches, some of our engineers have also become over time maintainers of specific areas of the Linux kernel. Recently, LWN.net conducted a study of how the patches merged in 4.4 went into the kernel, which shows the chain of maintainers who pushed the patches up to Linus Torvalds. Bootlin engineers had the following role in this chain of maintainers:

  • As a co-maintainer of the Allwinner (sunxi) ARM support, Maxime Ripard has submitted a pull request with one patch to the clock maintainers, and pull requests with a total of 124 patches to the ARM SoC maintainers.
  • As a maintainer of the RTC subsystem, Alexandre Belloni has submitted pull requests with 30 patches directly to Linus Torvalds.
  • As a co-maintainer of the AT91 ARM support, Alexandre Belloni has submitted pull requests with 46 patches to the ARM SoC maintainers.
  • As a co-maintainer of the Marvell EBU ARM support, Gregory Clement has submitted pull requests with a total of 33 patches to the ARM SoC maintainers.

Our contributions for the 4.4 kernel were centered around the following topics:

  • Alexandre Belloni continued some general improvements to support for the AT91 ARM processors, with fixes and cleanups in the at91-reset, at91-poweroff, at91_udc, atmel-st, at91_can drivers and some clock driver improvements.
  • Alexandre Belloni also wrote a driver for the RV8803 RTC from Microcrystal.
  • Antoine Ténart added PWM support for the Marvell Berlin platform and enabled the use of cpufreq on this platform.
  • Antoine Ténart did some improvements in the pxa3xx_nand driver, still in preparation to the addition of support for the Marvell Berlin NAND controller.
  • Boris Brezillon did a number of improvements to the sunxi_nand driver, used for the NAND controller found on the Allwinner SoCs. Boris also merged a few patches doing cleanups and improvements to the MTD subsystem itself.
  • Boris Brezillon enabled the cryptographic accelerator on more Marvell EBU platforms by submitting the corresponding Device Tree descriptions, and he also fixed a few bugs found in the driver
  • Maxime Ripard reworked the interrupt handling of per-CPU interrupts on Marvell EBU platforms especially in the mvneta network driver. This was done in preparation to enable RSS support in the mvneta driver.
  • Maxime Ripard added support for the Allwinner R8 and the popular C.H.I.P platform.
  • Maxime Ripard enabled audio support on a number of Allwinner platforms, by adding the necessary clock code and Device Tree descriptions, and also several fixes/improvements to the ALSA driver.

The details of our contributions for 4.4:

UN climate conference: switching to “green” electricity

Wind turbines in Denmark

The United Nations 2015 Climate Change Conference is an opportunity for everyone to think about contributing to the transition to renewable and sustainable energy sources.

One way to do that is to buy electricity that is produced from renewable resources (solar, wind, hydro, biomass…). With the worldwide opening of the energy markets, this should now be possible in most parts of the world.

So, with a power consumption between 4,000 and 5,000 kWh per year, we have decided to make the switch for our main office in Orange, France. But how to choose a good supplier?

Greenpeace turned out to be a very good source of information about this topic, comparing the offerings from various suppliers, and finding out which ones really make serious investments in renewable energy sources.

Here are the countries for which we have found Greenpeace rankings:
Australia France

If you find a similar report for your country, please let us know, and we will add it to this list.

Back to our case, we chose Enercoop, a French cooperative company only producing renewable energy. This supplier has by far the best ranking from Greenpeace, and stands out from more traditional suppliers which too often are just trading green certificates, charging consumers a premium rate without investing by themselves in green energy production.

The process to switch to a green electricity supplier was very straightforward. All we needed was an electricity bill and 15 minutes of time, whether you are an individual or represent a company. From now on, Enercoop will guarantee that for every kWh we consume from the power grid, they will inject the same amount of energy into the grid from renewable sources. There is no risk to see more power outages than before, as the national company operating and maintaining the grid stays the same.

It’s true our electricity is going to cost about 20% more than nuclear electricity, but at least, what we spend is going to support local investments in renewable energy sources, that don’t degrade the fragile environment that keeps us alive.

Your comments and own tips are welcome!

Linux 4.3 released, Bootlin contributions inside

Adelie PenguinThe 4.3 kernel release has been released just a few days ago. For details about the big new features in this release, we as usual recommend to read LWN.net articles covering the merge window: part 1, part 2 and part 3.

According to the KPS statistics, there were 12128 commits in this release, and with 110 patches, Bootlin is the 20th contributing company. As usual, we did some contributions to this release, though a somewhat smaller number than for previous releases.

Our main contributions this time around:

  • On the support for Atmel ARM SoCs
    • Alexandre Belloni contributed a fairly significant number of cleanups: description of the slow clock in the Device Tree, removal of left-over from platform-data usage in device drivers (no longer needed now that all Atmel ARM platforms use the Device Tree).
    • Boris Brezillon contributed numerous improvements to the atmel-hlcdc, which is the DRM/KMS driver for the modern Atmel ARM SoCs. He added support for several SoCs to the driver (SAMA5D2, SAMA5D4, SAM9x5 and SAM9n12), added PRIME support, and support for the RGB565 and RGB444 output configurations.
    • Maxime Ripard improved the dmaengine drivers for Atmel ARM SoCs (at_hdmac and at_xdmac) to add memset and scatter-gather memset capabilities.
  • On the support for Allwinner ARM SoCs
    • Maxime Ripard converted the SID driver to the newly introduced nvmem framework. Maxime also did some minor pin-muxing and clock related updates.
    • Boris Brezillon fixed some issues in the NAND controller driver.
  • On the support for Marvell EBU ARM SoCs
    • Thomas Petazzoni added the initial support for suspend to RAM on Armada 38x platforms. The support is not fully enabled yet due to remaining stability issues, but most of the code is in place. Thomas also did some minor updates/fixes to the XOR and crypto drivers.
    • Grégory Clement added the initial support for standby, a mode that allows to forcefully put the CPUs in deep-idle mode. For now, it is not different from what cpuidle provides, but in the future, we will progressively enable this mode to shutdown PHY and SERDES lanes to save more power.
  • On the RTC subsystem, Alexandre Belloni did numerous fixes and cleanups to the rx8025 driver, and also a few to the at91sam9 and at91rm9200 drivers.
  • On the common clock framework, Boris Brezillon contributed a change to the ->determinate_rate() operation to fix overflow issues.
  • On the PWM subsystem, Boris Brezillon contributed a number of small improvements/cleanups to the subsystem and some drivers: addition of a pwm_is_enabled() helper, migrate drivers to use the existing helper functions when possible, etc.

The detailed list of our contributions is:

Bootlin at the Linux Kernel Summit 2015

Kernel Summit 2012 in San DiegoThe Linux Kernel Summit is, as Wikipedia says, an annual gathering of the top Linux kernel developers, and is an invitation-only event.

In 2012 and 2013, several Bootlin engineers have been invited and participated to a sub-event of the Linux Kernel Summit, the “ARM mini-kernel summit”, which was more specifically focused on ARM related developments in the kernel. Gregory Clement and Thomas Petazzoni went to the event in 2012 in San Diego (United States) and in 2013, Maxime Ripard, Gregory Clement, Alexandre Belloni and Thomas Petazzoni participated to the ARM mini-kernel summit in Edinburgh (UK).

This year, Thomas Petazzoni has been invited to the Linux Kernel Summit, which will take place late October in Seoul (South Korea). We’re happy to see that our continuous contributions to the Linux Kernel are recognized and allow us to participate to such an invitation-only event. For us, participating to the Linux Kernel Summit is an excellent way of keeping up-to-date with the latest Linux kernel developments, and also where needed, give our feedback from our experience working in the embedded industry with several SoC, board and system vendors.

The quest for Linux friendly embedded board makers

Beagle Bone Black boardWe used to keep a list of Linux friendly embedded board makers. When this page was created in the mid 2000s, this page was easy to maintain. Though more and more products were created with Linux, it was still difficult to find good hardware platforms that were supported by Linux.

So, to help community members and system makers selecting hardware for their embedded Linux projects, we compiled a first selection of board makers that were meeting the below criteria:

  • Offering attractive and competitive products
  • At least one product supported Free Software operating systems (such as Linux, eCos and NetBSD.
  • At least one product meeting the above requirements, with a public price (without having to register), and still available on the market.
  • Specifications and documentation directly available on the website (no registration required). Engineers like to study their options on their own without having to share their contact details with salespeople who would then chase them through their entire life, trying to sell inappropriate products to them.
  • Website with an English version.

In the beginning, this was enough to reduce the list to 10-20 entries. However, as Linux continued to increase in popularity, and as hardware platform makers started to understand the value of transparent pricing and technical documentation, the criteria were no longer sufficient to keep the list manageable.

Therefore, we added another prerequisite: at least one product supported (at least partially) in the official version of the corresponding Free Software operating system kernel. This was a rather strong requirement at first, but only such products bring a guarantee for long term community support, making it much easier to develop and maintain embedded systems. Compare this with hardware supporting only a very old and heavily patched Linux kernel, for example, which software can only be maintained by its original developers. This also reveals the ability of the hardware vendor to work with the community and share technical information with its users and developers.

Then, with the development of low-cost community boards, and chip manufacturers efforts to support their hardware in the mainline Linux kernel, the list again became difficult to maintain.

The next prerequisite we could add is the availability as Open-source hardware, allowing customers to modify the hardware according to their needs. Of course, hardware files should be available without registration.

However, rather than keeping our own list, the best is to contribute to Wikipedia, which has a dedicated page on Open-Source computing hardware. At least, all the boards we could find are listed there, after adding a few.

Don’t hesitate to post comments to this page to share information about hardware which could be worth adding to this Wikipedia page!

Anyway, the good news is that Linux and Open-Source friendly hardware is now easier and easier to find than it was about 10 years back. Just have a preference for hardware that is supported in the mainline Linux kernel sources, or at least from a maker with earlier products which are already supported. A git grep -i command in the sources will help.

Embedded Linux internships at Bootlin in 2016

Penguin worksBootlin has internship topics to propose to people studying in French Universities or Engineering Schools:

If you already have a project related to embedded Linux you would like to contribute to, we are also open to your own suggestions!

See all details on our blog post in French.

Linux 4.2 released, Bootlin contributions inside

Adelie Penguin
Linus Torvalds has released last sunday the 4.2 release of the Linux kernel. LWN.net covered the merge window of this 4.2 release cycle in 3 parts (part 1, part 2 and part 3), giving a lot of details about the new features and important changes.

In a more recent article, LWN.net published some statistics about the 4.2 development cycle. In those statistics, Bootlin appears as the 10th contributing company by number of patches with 203 patches integrated, and Bootlin engineer Maxime Ripard is in the list of most active developers by changed lines, with 6000+ lines changed. See also this page for more kernel contribution statistics.

This time around, the most important contributions of Bootlin where:

  • Support for Atmel ARM processors:
    • The effort to clean-up the arch/arm/mach-at91/ continued, now that the conversion to the Device Tree and multiplatform is completed. This was mainly done by Alexandre Belloni.
    • Support for the ACME Systems Arietta G25 was added by Alexandre Belloni.
    • Support for the RTC on at91sam9rlek was also added by Alexandre Belloni.
    • Significant improvements were brought to the dmaengine xdmac and hdmac drivers (used on Atmel SAMA5D3 and SAMA5D4), bringing interleaved support, memset support, and better performance for certain use cases. This was done by Maxime Ripard.
  • Support for Marvell Berlin ARM processors:
    • In preparation to the addition of a driver for the ADC, an important refactoring of the reset, clock and pinctrl driver was done by using a regmap and the syscon mechanism to more easily share the common registers used by those drivers. Worked done by Antoine Ténart.
    • An IIO driver for the ADC was contributed, which relies on the syscon and regmap mentioned above, as the ADC uses registers that are mixed with the clock, reset and pinctrl ones.
    • The Device Tree files were relicensed under GPLv2 and X11 licenses.
  • Support for Marvell EBU ARM processors:
    • A completely new driver for the CESA cryptographic engine was contributed by Boris Brezillon. This driver aims at replacing the old mv_cesa drivers, by supporting the newer features of the cryptographic engine available in recent Marvell EBU SoCs (DMA, new ciphers, etc.). The driver is backward compatible with the older processors, so it will be a full replacement for mv_cesa.
    • A big cleanup/verification work was done on the pinctrl drivers for Armada 370, 375, 38x, 39x and XP, leading to a number of fixes to pin definitions. This was done by Thomas Petazzoni.
    • Various fixes were made (suspend/resume improvements, big endian usage, SPI, etc.).
  • Support for the Allwinner ARM processors:
    • Support for the AXP22x PMIC was added by Boris Brezillon, including the support for the regulators provided by this PMIC. This PMIC is used on a significant number of Allwinner designs.
    • A small number of Device Tree files were relicensed under GPLv2 and X11 licenses.
    • A big cleanup of the Device Tree files was done by using more aggressively the “DT label based syntax”
    • A new driver, sunxi_sram, was added to support the SRAM memories available in some Allwinner processors.
  • RTC subsystem:
    • As was announced recently, Bootlin engineer Alexandre Belloni is now the co-maintainer of the RTC subsystem. He has set up a Git repository at https://git.kernel.org/cgit/linux/kernel/git/abelloni/linux.git/ to maintain this subsystem. During the 4.2 release cycle, 46 patches were merged in the drivers/rtc/ directory: 7 were authored by Alexandre, and all other patches (with the exception of two) were merged by Alexandre, and pushed to Linus.

The full details of our contributions:

Bootlin talks at the Embedded Linux Conference Europe

Father Mathew BridgeThe Embedded Linux Conference Europe 2015 will take place on October 5-7 in Dublin, Ireland. As usual, the entire Bootlin engineering team will participate to the event, as we believe it is one of the great way for our engineers to remain up-to-date with the latest embedded Linux developments and connect with other embedded Linux and kernel developers.

The conference schedule has been announced recently, and a number of talks given by Bootlin engineers have been accepted:

We submitted other talks that got rejected, probably since both of them had already been given at the Embedded Linux Conference in California: Maxime Ripard’s talk on dmaengine and Boris Brezillon’s talk on supporting MLC NAND (which we regret since Boris is currently actively working on this topic, so we are expecting to have some useful results by the time of ELCE, compared to his ELC talk which was mostly a presentation of the issues and some proposals to address them). Interested readers can anyway watch those talks and/or read the slides.

In addition to the Embedded Linux Conference Europe itself:

  • Thomas Petazzoni will participate to the Buildroot developers meeting on October 3/4, right before the conference.
  • Alexandre Belloni will participate to the OEDEM, the 2015 OpenEmbedded Developer’s European Meeting, taking place on October 9 after the conference.

2015 Q2 newsletter

Bootlin working on the $9 computer!

NextThing Co, a company based in Oakland, California, made the news in the last months by starting a successful crowdfunding campaign to develop a $9 computer! Much like the Raspberry Pi, this $9 computer called C.H.I.P is based on an ARM processor and runs a Linux operating system.

More specifically, at the core of this computer is an Allwinner ARM processor, and Bootlin engineer Maxime Ripard turns out to be the official Linux kernel maintainer for the support of this processor family. Since NextThing Co. is firmly engaged in having software support for the C.H.I.P that is as open-source as possible, they decided to contract us to do a lot of work in the official Linux kernel to improve the support for the Allwinner processor they are using.

Thanks to this project, some of the big missing features in the support of Allwinner processors in the official Linux kernel will be implemented in the coming months, so you can expect to see a lot of contributions from Bootlin on such topics in the future. We’re really excited to be part of the $9 computer adventure!

See our blog post for more details.

Kernel contributions

As usual, we continue to contribute significantly to the Linux kernel, with 100 to 200 or more patches from Bootlin engineers merged at each kernel release. Our focus continues to be on support for various ARM processor families.

  • In Linux 3.19, we had 205 patches merged, making Bootlin the 13th contributing company in number of patches. See details on our 3.19 contributions.
  • In Linux 4.0, we had 252 patches merged, making Bootlin the 6th contributing company in number of patches. See details on our 4.0 contributions.
  • In Linux 4.1, we had 118 patches merged, a smaller amount of contributions. See details.

Some major highlights of our contributions:

  • In Linux 4.0, we merged a complete driver for the display controller of the latest Atmel ARM processors. This DRM/KMS driver, written by Boris Brezillon, allows using the display of those processors with the mainline kernel. It was the last big feature missing in the mainline kernel for the Atmel processors.
  • Our engineer Alexandre Belloni was appointed as the co-maintainer of the RTC subsystem, and also as the co-maintainer of the support for the Atmel processors. As the maintainer of the RTC subsystem, Alexandre is now sending pull requests directly to Linus Torvalds!
  • In Linux 4.1, we completed the conversion of Atmel platform support to the multiplatform paradigm. And we also added support for the latest Armada 39x processor from Marvell.

New training session on Buildroot

Last year, we developed and released a new 3-day training session on the Yocto Project and OpenEmbedded. This year, we are happy to release a new 3-day training course covering the Buildroot embedded Linux build system.

Buildroot is very popular alternate solution to the Yocto Project to build embedded Linux systems, thanks to its ease of use and Buildroot, with Bootlin CTO Thomas Petazzoni being one of the top contributors to the project.

Over the 3 days of this training course, you will learn how to use Buildroot, how to add more packages, how to customize the filesystem generated by Buildroot, how Buildroot works internally and much more!

Check out our agenda, slides, and practical lab instructions for more details.

This training session, taught by Thomas, can be delivered anywhere in the world at your location, or individual participants can attend to our first public training session on this topic in Toulouse (France) in November 2015.

Recent projects

Besides our visible contributions, we also work on a number of projects for customer-specific platforms.

For a French customer making a custom i.MX6 base-board using a System-on-Module from SECO, we ported a recent mainline U-Boot, a 3.10 Freescale kernel, and provided a Buildroot based system with Qt5 and OpenGL acceleration to allow the customer to develop its own applications. Among other things, we had to add support for communication with an FPGA over SPI, and wrote a userspace tool to reprogram this FPGA over SPI.

This project lead to a few U-Boot contributions (support for the SECO module):

And a few Buildroot contributions as well:

For a US based customer, developed a prototype system running on a Nitrogen 6x platform, built by Buildroot, and running the SuperCollider application for audio synthesis.

For a French customer, developed a Yocto Project based BSP for a custom i.MX6 platform. The work involved kernel development to adapt to the hardware and run some Qt5 application under X11.

Conferences

Like we do every year, we participated to the Embedded Linux Conference in San Jose, California: seven engineers from Bootlin attended the conference.

The videos and slides of the three talks we gave have been posted:

  • The DMAengine subsystem, by Maxime Ripard (slides, video).
  • The Device Tree as a stable ABI: a fairy tale?, by Thomas Petazzoni (slides, video).
  • MLC/TLC NAND support: (new ?) challenges for the MTD/NAND subsystem, by Boris Brezillon (slides, video)

For more details about our participation to ELC, see our blob post.

We have submitted several talks for the upcoming Embedded Linux Conference Europe, which will take place early October in Dublin, Ireland.

Upcoming public training sessions

In addition to offer our training courses on-site everywhere in the world (we recently delivered training in the United States, Israel, India and Mexico!), we also offer public training sessions opened to individuals. Our next public training sessions are:

Embedded Linux training
October 12-16, in Avignon (France), in English
November 23-27, in Toulouse (France), in French
Embedded Linux kernel and driver development training
July 20-24, in Avignon (France), in English
November 16-20, in Toulouse (France), in French
Embedded Linux development with Buildroot training
November 30-December 2, in Toulouse (France), in English
Yocto Project and OpenEmbedded development training
October 13-15, in Toulouse (France), in English
Android system development training
December 7-10, in Toulouse (France), in English

Recruiting

At Bootlin, we are starting to get more and more requests for very cool projects. As it can be very frustrating to turn down very interesting opportunities, we have decided to look for new engineers to join our technical team.

Therefore, if you are a junior engineer showing a real interest in embedded Linux and open-source projects, or an experienced engineer with existing visible contributions and embedded Linux knowledge, do not hesitate to contact us.

See more details about our job openings.