kernel – Page 8

2016 Q1 newsletter

The Bootlin team wishes you a Happy New Year for 2016, with many new bits to enjoy in your life!

Bootlin is happy to take this opportunity to share some news about the latest training and contribution activities of the company.

Bootlin work on the $9 computer

As announced in our previous newsletter, Bootlin has been working intensively on developing the low-level software support for the first $9 computer, the C.H.I.P by Next Thing Co.

Next Thing Co. has successfully delivered an initial batch of platforms in September to the early adopters, and has started shipping the final products in December to thousands of Kickstarter supporters.

Those products are using the U-Boot and Linux kernel ported by Bootlin engineers, with numerous patches submitted to the official projects and more to be submitted in the coming weeks and months:

Support for the C.H.I.P platform itself, in U-Boot and in the Linux kernel;
Support for audio on Allwinner platforms added to the Linux kernel;
Development of a DRM/KMS driver for the graphics controller found on Allwinner platforms;
Significant research effort on finding appropriate solutions to support Multi-Level Cell NANDs in the Linux kernel;
Enabling of the NAND storage in Single-Level Cell mode, until the Multi-Level Cell mode can be enabled reliably;
Addition of NAND support in the fastboot implementation of U-Boot, which is used to reflash the C.H.I.P.

We will continue to work on the C.H.I.P over the next months, with among other things more work on the graphics side and the NAND side.

Kernel contributions

The primary focus of the majority of our customer projects remain the Linux kernel, to which we continue to contribute very significantly.

Linux 4.2

We contributed 203 patches to this release, with a new IIO driver for the ADC found on Marvell Berlin platforms, a big cleanup to the support of Atmel platforms, improvements to the DMA controller driver for Atmel platforms, a completely new driver for the cryptographic accelerator found on Marvell EBU platforms.

In this cycle, our engineer Alexandre Belloni became the official maintainer of the RTC subsystem.

See details on our contributions to Linux 4.2

Linux 4.3

We contributed 110 patches to this release, with mainly improvements to the DRM/KMS driver and DMA controller driver for Atmel platforms and power management improvements for Marvell platforms.

See details on our contributions to Linux 4.3

Linux 4.4

We contributed 112 patches to this release, the main highlights being an additional RTC driver, a PWM driver, support for the C.H.I.P platform, and improvements to the NAND support.

See details on our contributions to Linux 4.4

Work on ARM 64-bit platform

We have started to work on supporting the Linux kernel on several ARM 64 bits platforms from different vendors. We will be submitting the initial patches in the coming weeks and will progressively improve the support for those platforms throughout 2016 where a major part of our Linux kernel contribution effort will shift to ARM 64-bit.

Growing engineering team

Our engineering team, currently composed of six engineers, will be significantly expanded in 2016:

Two additional embedded Linux engineers will join us in March 2016 and will be working with our engineering team in Toulouse, France. They will help us on our numerous Linux kernel and Linux BSP projects.
An engineering intern will join us starting early February, and will work on setting up a board farm to contribute to the kernelci.org automated testing effort. This will help us do more automated testing on the ARM platforms we work on.

Upcoming training sessions

We have public training sessions scheduled for the beginning of 2016:

Embedded Linux development training: February 29 – March 4, in English, in Avignon (France)
Embedded Linux kernel and driver development training: March 14-18, in English, in Avignon (France)
Android system development training: March 7-10, in English, in Toulouse (France)

We also offer the following training courses, on-site, anywhere in the world, upon request:

Embedded Linux development
Embedded Linux kernel and driver development
Android system development
Yocto Project and OpenEmbedded development
Embedded Linux development with Buildroot

Conferences

We participated to the Embedded Linux Conference Europe in Dublin in October 2015, and gave a number of talks:

Supporting Multi-Function Devices in the Linux Kernel: A Tour of the mfd, regmap and syscon APIs, by Alexandre Belloni (slides, video)
Kernel Maintainership: An Oral Tradition, by Grégory Clement (slides, video)
Learning the basics of Buildroot, by Thomas Petazzoni (slides, video)
Keynote: Linux Kernel SoC Support Mainlining Tips (By a Bunch of Other French People), by Thomas Petazzoni (slides)

In addition, our engineer Thomas Petazzoni was invited to the Linux Kernel Summit, an invitation-only conference for the kernel maintainers and developers. He participated to the three days event in Seoul, South Korea. See Bootlin at the Linux Kernel Summit 2015.

At the beginning of 2016, our entire engineering team will be attending the Embedded Linux Conference in San Diego (US), which means that no less than 9 engineers from Bootlin will be present at the conference!

Porting Linux on ARM seminar

In December 2015, we gave a half-day seminar entitled “Porting Linux on ARM” in Toulouse (France). The materials, in English, are now freely available on our web site.

Seminar “Porting Linux on an ARM board”, materials available

On December 10th 2015, Bootlin engineer Alexandre Belloni gave a half-day seminar on the topic of Porting Linux on an ARM board in Toulouse, France. This seminar covers topics like porting the bootloader, understanding the concept of the Device Tree, writing Linux device drivers and more. With ~50 persons from various companies attending and lots of questions from the audience, this first edition has been very successful, which shows an increasing interest for using Linux on ARM platforms in the industry.

We are now publishing the 220 slides materials from this seminar, available in PDF format. Like all our training materials, this material is published under the Creative Commons BY-SA 3.0 license, which allows everyone to re-use it for free, provided the derivative works are released under the same license. We indeed re-used quite extensively parts of our existing training materials for this half-day seminar.

We plan to give this half-day seminar in other locations in France in 2016. Contact us if you are interested in organizing a similar seminar in your area (we are happy to travel!).

Linux 4.4, Bootlin contributions

Linux 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:

Linux 4.3 released, Bootlin contributions inside

The 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

The 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.

Linux 4.1 released, Bootlin 17th contributing company

Linus Torvalds recently released the 4.1 Linux kernel, for which LWN.net gave a good description of the major new features: 4.1 Merge window, part 1, 4.1 Merge window, part 2, The 4.1 merge window closes.

As usual, Bootlin engineers contributed to the Linux kernel during this development cycle, though this time with a smaller number of patches: we contributed 118 patches. This time around, Bootlin is the 17th company contributing to this kernel release, by number of patches.

Our major contributions this time around have been:

On support for Atmel platforms
- Alexandre Belloni did a good number of improvements to Atmel SoC support: converting some remaining SoCs to the SoC detection infrastructure, cleaning up the timer driver to use a syscon/regmap, removing a lot of unused headers in arch/arm/mach-at91/, etc. The final and very important change is that the AT91 ARM platform is now part of the multiplatform mechanism: you can build a single zImage for ARMv5 or for ARMv7 which will include support for the ARMv5 or ARMv7 Atmel platforms.
- Boris Brezillon improved the Atmel DRM/KMS driver for the display controller by switching to atomic mode-setting. He also added Device Tree definitions for the Atmel display controller on Atmel SAMA5D3 and Atmel SAMA5D4.
On support for Marvell EBU platforms
- Ezequiel Garcia enabled the Performance Monitor Unit on Armada 375 and Armada 38x, which allows to use perf on those platforms.
- Gregory Clement did a number of fixes and minor improvements to support for Marvell EBU platforms.
- Maxime Ripard enabled the Performance Monitoring Unit on Armada 370/XP, enabling the use of perf on these platforms. He also improved support for the Armada 385 AP board by enabling NAND and USB3 support.
- Thomas Petazzoni added initial support for the new Marvell Armada 39x platform (clock driver, pinctrl driver, Device Tree). He did some cleanup and fixes in many Device Tree of Marvell EBU platforms and added suspend/resume support in the PCI and pinctrl drivers for these platforms.
Other contributions
- As we posted recently, Alexandre Belloni also became in this release cycle a co-maintainer for the RTC subsystem.
- Alexandre Belloni added bq27510 support for the bq27x00_battery driver.
- Maxime Ripard did some small contributions to the dmaengine subsystem, improved the of_touchscreen code and the edt-ft5x06 touchscreen driver, and did some cleanup in the Allwinner sun5i clocksource driver.

For the upcoming 4.2 version, we have 198 patches in linux-next, of which 191 have already been pulled by Linus as part of the 4.2 merge window.

Our complete list of contributions follows:

Bootlin working on the $9 C.H.I.P. computer

If you’re following the news about embedded Linux and new cool development platforms, you for sure couldn’t miss the announcement on the world’s first $9 computer. This computer, called C.H.I.P., was started through a crowd-funding campaign on Kickstarter and reception in the Free Software and Open Source community has been very positive. Out of an initial funding goal of $50,000, NextThing Co, the Oakland, California based company creating this product eventually managed to raise more $2,000,000 of funding.

NextThing Co announced their intention to support the platform in the most open way possible: the schematics will be made available, and it will be supported in the mainline Linux kernel.

It turns out that the processor NextThing Co has chosen for this platform is an Allwinner R8 processor. Bootlin has been working since several years on supporting Allwinner processors in the mainline Linux kernel: our engineer Maxime Ripard is the maintainer of the Allwinner SoC support.

Thanks to this long term involvement, Bootlin has been asked by NextThing Co to work with them to support the C.H.I.P. computer in the mainline Linux kernel, and in the process bring some significant improvements to the support of Allwinner processors in the kernel.

NextThing Co announced recently our collaboration in a blog post on Kickstarter:

We’re incredibly excited to announce that we’ve partnered with one of the premier contributors to ARM Linux: Bootlin! We will be collaborating with their amazing team of ARM Linux engineers, and of course our Kernel Hacker backers to help us test and mainline C.H.I.P.’s kernel modifications as we move forward.

Bootlin is also very excited to be working with NextThing Co on this project! Thanks to this, over the next months, we will have a very substantial amount of time dedicated to this project, and we will regularly push code to support the missing hardware Allwinner SoC hardware blocks in the mainline Linux kernel and to support the C.H.I.P. board.

More details about the C.H.I.P:

Availability planned for 2016 for the general public. A selection of 1000 kernel hackers who backed on Kickstarter will have the platform earlier.
Very small platform: 40mm x 60mm, making is even smaller than a Raspberry Pi or BeagleBone.
Allwinner R8 processor, clocked at 1 Ghz, and offering OpenGL/OpenVG acceleration through an ARM Mali GPU
512 MB of RAM
4GB of on-board NAND flash storage
WiFi and Bluetooth 4.0 to connect the system to the outside world
One USB host port
Powered through a micro USB connector which also supports USB OTG (either USB host or device).
Jack connector for composite video out, headphones and microphone input.
Many headers to connect external devices (SPI, I2C, UART + 8 GPIOs)
Integrated circuit for charging a LiPo battery and being powered by it
Additional HDMI or VGA add-on boards will be needed to connect to displays with the corresponding connectivity.

Bootlin engineer Alexandre Belloni co-maintainer of Linux Atmel processor support

After becoming the co-maintainer of the Linux RTC subsystem, Bootlin engineer Alexandre Belloni also recently became a co-maintainer for the support of Atmel ARM processors in the Linux kernel.

Bootlin has been working since early 2014 with Atmel to improve support for their processors in the mainline kernel. Since this date, our work has mainly consisted in:

Modernizing existing code for Atmel processors: complete the switch to the Device Tree and the common clock framework for all platforms, rework all that was needed to make Atmel processor support compatible with the ARM multiplatform kernel, and do a lot of related driver and platform refactoring.
Implement a complete DRM/KMS driver for the display subsystem of the most recent Atmel processors.
Upstream support for the Atmel SAMA5D4, the latest Cortex-A5 based SoC from Atmel.

Thanks to this long-term involvement from Alexandre Belloni and Boris Brezillon, Alexandre was appointed as a co-maintainer of Atmel support, replacing Andrew Victor who hasn’t been active in kernel development since quite some time. He is joining Nicolas Ferre and Jean-Christophe Plagniol-Villard in the team of maintainers for the Atmel platform.

Alexandre has sent his first pull request as an Atmel co-maintainer on May 22, sending 9 patches to the ARM SoC maintainers, planned for the 4.2 kernel release. His pull request was quickly merged by ARM SoC maintainer Arnd Bergmann.

Bootlin is proud to have one of its engineers as the maintainer of one very popular embedded Linux platform, which has had since many years a strong commitment of upstream Linux kernel support. Alexandre is the third Bootlin engineer to become an ARM platform maintainer: Maxime Ripard is the maintainer of Allwinner ARM processor support, and Gregory Clement is the co-maintainer of Marvell EBU ARM processor support.

Embedded Linux and kernel job openings for 2015

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 (such as projects that allow us to contribute to the Linux kernel, Buildroot or Yocto Projects), we have decided to look for new engineers to join our technical team.

Job description in a nutshell

Technical aspects: mainline Linux kernel development, Linux BSP and embedded Linux system integration, technical training
Location: working in one of our offices in France (Toulouse or Orange)
Contract: full-time, permanent French contract

Mainline Linux kernel development

Believe it or not, we now have an increasing number of customers contracting us to support their hardware in the mainline Linux kernel. They are either System on Chip manufacturers or systems makers, who now understand the strong advantages brought by mainline Linux kernel support to their customers and to themselves.

You can see the results: Bootlin is now consistently in the top 20 companies contributing to the Linux kernel. We are even number 6 for Linux 4.0!

Note that this job doesn’t only require technical skills. It also has a strong social dimension, having to go through multiple iterations with the community and with kernel subsystem maintainers to get your code accepted upstream.

Linux BSP and embedded Linux system integration

Such activity involves developing and integrating everything that’s needed to deploy Linux on the customer hardware: bootloader, kernel, build environment (such as Buildroot or the Yocto project), upgrade system, optimizing performance (such as boot time) and fixing issues. Another way is to provide guidance and support to customer learning to do such a job.

As opposed to Linux kernel development projects which are often long term ones (though with step by step objectives which can be reached in days), these are usually shorter and more challenging projects. They allow us to stay in touch with the real-life challenges that customer engineers face every day, and that require to achieve substantial results in a relatively small number of days.

Such projects also constitute opportunities to contribute improvements to the mainline kernel and bootloader projects, as well to the build system projects themselves (Buildroot, Yocto Project, OpenWRT…).

Training and sharing experience

Knowledge sharing is an important part of Bootlin mission and activity. Hence, after gaining sufficient on-the-job experience, another important aspect of the job is teaching, maintaining and improving Bootlin training courses.

You will also be strongly incited to share your technical experience by writing blog posts or kernel documentation, and by proposing talks at international conferences, especially the Embedded Linux Conference (USA, Europe).

Profile

Experience: we are open to both experienced engineers and people just out of engineering schools. Though prior experience with the technical topics will be an advantage, we are also interested in young engineers demonstrating great potential for learning, coding and knowledge sharing. People having made visible contributions in these areas will have an advantage too.
Language skills: fluency in oral and written English is very important. French speaking skills won’t be a requirement, but an advantage too.
Traveling: for training sessions and conference participation, you will need the ability to travel rather frequently, up to 8-10 times a year.
Ability to relocate, to one of our offices in France, either in Toulouse or in Orange, to strengthen our engineering teams here.

Details about Toulouse and Orange

Toulouse is a dynamic city with lots of high-tech and embedded systems companies in particular. Our office in Colomiers can easily be reached by train from downtown Toulouse if you wish to settle there. You would be working with Boris Brezillon, Antoine Ténart, Maxime Ripard and our CTO Thomas Petazzoni.
Our main office is settled in Orange in the heart of the Provence region, close to Avignon, a smaller but dynamic city too. It enjoys a sunny climate and the proximity of the Alps and the Mediterranean sea. Accommodation is very affordable and there are no traffic issues! You would be working with our founder Michael Opdenacker and of course remotely with the rest of the engineering team. In particular, we are interested in foreign engineers who could help us develop our services in their home countries.

We prefer not to offer home based positions for the moment, which have their own complexity and cost, while we have plenty of space left in our current offices.

See a full description and details about how to contact us.

Bootlin engineer Alexandre Belloni co-maintainer of the Linux RTC subsystem

The Linux RTC subsystem supports the Real Time Clock drivers for a large number of platforms and I2C or SPI based Real Time Clocks: it contains about 140 different device drivers, plus the RTC core itself. The current maintainer, Alessandro Zummo, had unfortunately very little time to address all the patches that were sent, and many of them where usually handled by Andrew Morton, acting as a fallback for various parts of the kernel that are not enough actively maintained.

To address this lack of maintainer time, Bootlin engineer Alexandre Belloni recently became a co-maintainer of the RTC subsystem, as can be seen in this patch to the MAINTAINERS file. Alexandre has already started his work by cleaning up the patchwork instance listing all the pending RTC patches, reducing the number of pending patches from 2843 to 436, actively applying new patches being posted, and reviving old patches that never got any attention.

Up to the 4.1 release included, RTC patches will flow to Linus Torvalds through Andrew Morton, but starting from Linux 4.2, Alexandre will start sending his pull requests directly to Linus.