Linux 5.1 released, Bootlin contributions

Linux Linux 5.1 was released a a few days ago by Linus Torvalds. As usual, LWN covered the major new features of this release by looking at what got merged during the merge window: part 1 and part 2. KernelNewbies also has a nice summary.

Bootlin contributed 181 commits to this release, making us the 14th contributing company by number of commits. Taking the entire Git history of the kernel, Bootlin has contributed a total of 6256 patches, making us the 15th contributing company by number of commits: a demonstration of our long-term involvement in the upstream Linux kernel community.

For Linux 5.1, our significant contributions have been:

In the RTC subsystem
- Alexandre Belloni contributed a new RTC driver for the RV3028 RTC
- Alexandre Belloni, as the maintainer of the RTC subsystem, continued to contribute a number of fixes/improvements in various RTC drivers
As part of a customer project in which we ported a modern U-Boot and Linux to a custom NXP LPC3250 platform, Alexandre Belloni contributed a fix for the LPC3250 serial port driver, and Grégory Clement moved the LPC3250 Analog-to-Digital converter Device Tree binding out of staging. We have other patches/fixes related to LPC3250 in the pipeline.
In the support for Marvell platforms
- Antoine Ténart contributed numerous improvements to the mvpp2 driver, especially to properly handle the reset state of the different hardware blocks depending on how a particular Ethernet port is configured.
- Grégory Clement contributed a new cpufreq driver to support CPU frequency scaling on Marvell Armada 8K
- Maxime Chevallier contributed numerous improvements to the marvell10g Ethernet PHY driver, mainly to support 2.5G and 5G speeds, and to support the 88E2110 PHY. He also enabled 2.5G support in the mvpp2 Ethernet MAC driver.
- Miquèl Raynal continued his work to bring suspend/resume support to the Armada 37xx platform: he added support for the Armada 37xx COMPHY and Armada 37xx USB UTMI PHY, added suspend/resume in ehci-orion, improved the USB core code to use the generic PHY API, and did a number of related Device Tree changes.
In the support for RaspberryPi platforms
- Boris Brezillon made some fixes in the vc4 display controller driver: support for X/Y reflection was added, negative X/Y positioning was fixed, and support for margins on HDMI displays was added.
In the support for Allwinner platforms
- Maxime Ripard made a number of small improvements to the Allwinner display controller driver
- Paul Kocialkowski contributed a number of improvements to the support of YUV planes in the Allwinner display controller driver, in relation to our work on the Allwinner VPU support.
- Paul Kocialkowski contributed some Device Tree changes to enable the Allwinner VPU on Allwinner A10, as well as a few fixes for the Allwinner VPU driver itself.
- As listed below, Boris Brezillon converted the Allwinner NAND controller driver to the exec_op interface.
After extending the generic PHY subsystem in Linux 5.0 with two new hooks phy_configure() and phy_validate(), Maxime Ripard used this extension to add a driver for the Cadence D-PHY (used in combination with Cadence MIPI DSI and CSI transceivers), to convert the Allwinner A31 DSI D-PHY handling to the generic PHY subsystem, and converted the Cadence DSI driver to use the generic PHY API.
In the MTD subsystem
- The NAND controller driver for Allwinner platform was converted to the use the new exec_op interface by Boris Brezillon.
In the GPIO subsystem
- Thomas Petazzoni added support in the core GPIO subsystem to enable pull-up/pull-down resistors available in some GPIO controllers. It was contributed together with an implementation for the PCA953x family of I2C GPIO expanders.

In addition to writing code and submitting patches, a number of Bootlin engineers are also maintainers of various areas in the Linux kernel. As part of their maintainer duties, they review and merge patches from other developers:

Maxime Ripard, as the Allwinner platform maintainer, merged 76 patches from other developers
Alexandre Belloni, as the RTC subsystem maintainer and Atmel/Microchip platform co-maintainer, merged 53 patches from other developers
Miquèl Raynal, as the NAND subsystem maintainer, merged 38 patches from other developers
Grégory Clement, as the Marvell platform maintainer, merged 18 patches from other developers

And finally, here is as usual the detailed list of each patch we contributed:

Embedded Linux system development course on STM32MP1 Discovery

For many years, Bootlin has been offering an Embedded Linux system development training course, which has been delivered world-wide to hundreds of engineers by Bootlin trainers. This course is the most appropriate one for engineers getting started with embedded Linux: it goes through all the software layers of an embedded Linux system, from the toolchain to the application, through the bootloader, Linux kernel and basic user-space. With numerous hands-on labs, attendees get practical experience during this training, and learn how to build their embedded Linux system from the ground-up.

This course has been available for a while in two variants:

A 5-day variant, which covers all topics, including flash storage and filesystems as well as-real time
A 4-day variant, which is identical to the 5-day variant, except that flash storage and filesystem and real-time are not covered

Embedded Linux system development Today, we are happy to announce that all the practical labs of our 4-day variant are now done on the recently announced STM32MP157 Discovery board, which uses the STM32MP157 processor from STMicroelectronics. This processor has a number of interesting features for a large number of embedded applications, as we discussed in a previous blog post.

Just like for all our training courses, the training materials for this course are publicly and freely available:

Detailed agenda
Slides
Practical labs
Github repository with the training materials source code

Bootlin trainers are available to deliver this course on-site anywhere in the world. See this page for more details.

STM32MP1 system-on-chip, Bootlin member of ST Partners program

Earlier this year at Embedded World, STMicroelectronics announced the release of their first MPU, the STM32MP1 system-on-chip. Bootlin has been selected as one of the companies offering engineering and training services to be part of the ST Partners program around this new platform. In this blog post, we will give more details about STM32MP1 and Bootlin’s initial efforts on this platform.

The STM32MP1 platform

For the past several years, STMicroelectronics has developed a range of 32-bit microcontrollers based on the ARM Cortex-M cores. The most high-end ones, based on Cortex-M4 and M7, were powerful enough to run a Linux operating system with external RAM attached, and ST has been very active in adding support for these micro-controllers in the upstream U-Boot and Linux projects. However, the Cortex-M4 and M7 being MMU-less processor cores, Linux could work only with a number of limitations, preventing from using some complex Linux software stacks.

With the STM32MP1, ST is now offering a full-featured microprocessor, based on the combination of one or two Cortex-A7 cores (650 Mhz), one Cortex-M4 core (209 Mhz) and a wide variety of peripherals. The STM32MP1 is currently available in 3 variants:

STM32MP151, featuring one Cortex-A7, one Cortex-M4, and the common set of peripherals
STM32MP153, featuring two Cortex-A7, one Cortex-M4, the common set of peripherals plus CAN-FD
STM32MP157, featuring two Cortex-A7, one Cortex-M4, the common set of peripherals plus a 3D GPU, a DSI display interface and CAN-FD

The hardware blocks integrated in the STM32MP1 offers a large amount of features and connectivity options:

External DDR controller, supporting up to LPDDR2/3 and DDR3
QuadSPI memory interface
NAND flash controller, with built-in ECC capability
6 I2C controllers
4 UARTs and 4 USARTs
6 SPI controllers
4 SAI audio interfaces
HDMI-CEC interface
3 SD/MMC controllers
2 CAN controllers
2 USB host + 1 USB OTG controllers
1 Gigabit Ethernet MAC
Camera interface (parallel)
2 ADCs, 2 DACs, 1 digital filter for sigma delta modulators
LCD controller supporting up to 1366×768
GPU from Vivante (which means open-source support is available!)
MIPI DSI
Plenty of timers
Crypto accelerators, random number generator (only in the C variants of the SoC)
Secure boot (only in the C variants of the SoC)

This combination of a wide range of connectivity options, graphics support with GPU support, and a Cortex-M4 for real-time logic, makes the STM32MP1 interesting for a large number of applications.

Software support for the STM32MP1

Bootlin being a consulting company specialized in low-level Linux software for embedded platforms, it is obviously a key aspect we looked at for the STM32MP1 platform.

First of all, a number of hardware blocks used in the STM32MP1 platform were already used on previous micro-controllers from ST and were therefore already supported in upstream projects such as U-Boot and Linux. The fact that these micro-controller products can run upstream versions of U-Boot and Linux is a good indication of ST’s strategy in terms of upstream support.

Then, even before the STM32MP1 product was publicly announced, a significant number of ST engineers had already started contributing to upstream TF-A, U-Boot and Linux the support for various pieces needed for the STM32MP1. Even if the support is not entirely upstream at this point, this strategy of starting the upstreaming effort ahead of the product announcement is very good.

Even though the work towards open-source GPU support has tremendously progressed over the past years, GPUs were notoriously known for being difficult to support in a fully open-source software stack. It is interesting to see that ST has chosen the GPU from Vivante for this STM32MP1, as Vivante is one of the first embedded GPU supported by Mesa, the open-source OpenGL implementation. Vivante GPUs are already used in a number of other SoCs, especially from NXP, and the Vivante open-source support, called etnaviv has therefore already seen some significant usage in production.

Until all the support for the STM32MP1 is fully upstreamed, ST provides publicly available Git repositories for all pieces of the software stack:

In addition to the availability of the code, there is also plenty of documentation available in the Development zone of the STM32 MPU wiki.

Hardware platforms for the STM32MP1

ST provides a low-cost evaluation platform called Discovery, available in two versions:

STM32MP157A-DK1, which features the STM32MP157A processor (all features, but without secure boot), LEDs, push buttons, Ethernet, one USB-C connector, 4 USB-A connectors, HDMI, microSD, analog audio, Arduino and RPi compatible connectors. The cost is $69.
STM32MP157C-DK2 features the STM32MP157C processor (all features including secure boot), and has the same features as the DK1 variant, with the addition of a DSI panel with touch and a WiFi/Bluetooth chip. The cost is $99.

ST also provides some more feature-complete evaluation boards: the STM32MP157A-EV1 and STM32MP157C-EV1, which only differ by the lack or availability of secure boot support. They offer more hardware features than the Discovery platforms, and are obviously available at a higher cost, $399.

In addition to these platforms provided by ST, several manufacturers have already announced a number of boards or system-on-module based on the STM32MP1:

emSTAMP-Argon system on module from Emtrion
SOM-STM32MP157 system on module from Kontron
Shiratec 96Boards IoT Edition Extended compatible board with the STM32MP157 processor
OSD32MP15x system-in-package from Octavo Systems, which integrates in a single package the STM32MP157 processor, its PMIC, a DDR chip and the necessary power circuitry.

Bootlin member of ST’s partner program

Bootlin is proud to have been chosen by ST to be part of its partner program when the STM32MP1 platform was announced. As a software partner, Bootlin can offer its training and engineering services to customers using the STM32MP1. We can provide:

Engineering for the development of Linux Board Support Packages for STM32MP1 platforms: porting U-Boot, porting Linux, writing Linux device drivers, delivering a fully integrated and optimized Linux system generated with Yocto or Buildroot
Training on embedded Linux, Linux kernel development and Yocto usage around the STM32MP1 platform

Bootlin trainings on STM32MP1

As a ST partner, Bootlin will be porting two of its existing training courses to the STM32MP1 platform: this means that all the practical labs in those courses will take place on the STM23MP157 Discovery board. We will soon be announcing:

Our 4-day embedded Linux system development course, on STM32MP1
Our 3-day Yocto Project and OpenEmbedded development course, on STM32MP1

Of course, as Bootlin has always done, all the training materials will be made freely available, under the same Creative Commons license we already use for existing training materials.

Building a Linux system for STM32MP1

The STM32MP1 being the first micro-processor in this family of SoCs from ST, a number of companies will most likely migrate from a micro-controller environment to a micro-processor one. This means moving from a situation where only a bare-metal application or a simple RTOS is used, to a situation where a feature-rich operating system such as Linux is being used. This migration is not always trivial as it requires gaining a lot of knowledge about U-Boot, the Linux kernel, Linux system integration and development, and more.

In order to help with this, in addition to the training courses described above, we will soon start publishing a series of blog posts that describe step by step how to build a Linux system for the STM32MP157 Discovery Kit, all the way up to reading data from an I2C sensor, and displaying them in a Qt5 based application. Stay tuned on our blog for those articles in the next few weeks!

Buildroot training course updated: Buildroot 2019.02, BeagleBone Black Wireless

Buildroot logo Bootlin has been for many years a key contributor to the Buildroot project, a very popular embedded Linux build system. A few years ago, we decided to share our Buildroot expertise by creating a corresponding training course: Embedded Linux development with Buildroot, for which the training materials are freely available, under a Creative Commons license.

We have recently updated this training course up to Buildroot 2019.02, which is the latest “long term support” release of the project. Both the lectures and practical labs have been updated to this Buildroot version.

In addition, the board used in the course has been changed to the BeagleBone Black Wireless, instead of the BeagleBone Black, which is no longer easily available. The practical labs were updated accordingly, and we now use the USB device interface to provide network connectivity between the development PC and the embedded target.

This 3-day Buildroot training course can be delivered on-site at your location, anywhere in the world. See our cost and registration page for more details.

Linux 5.0 released, Bootlin contributions

Linux 5.0 was released two weeks ago by Linus Torvalds, and as it is now always the case, Bootlin has contributed a number of patches to this release. For an overview of the new features and improvements brought by Linux 5.0, we as usual recommend to read the LWN articles: merge window summary part 1, merge window summary part 2. The KernelNewbies.org page about this kernel release is also nicely documented.

In terms of contribution to Linux 5.0, according to the LWN statistics, Bootlin is the 12th contributing company by number of commits (261 commits), and 8th contributing company by number of changed lines. Bootlin engineer Maxime Ripard is 11th contributing developer by number of commits, and former Bootlin engineer Boris Brezillon is 12th contributing developer by number of commits, and 8th by number of changed lines. In this release, we are also happy to see numerous contributions from Paul Kocialkoswki who joined Bootlin in November 2018 after his internship working on the Linux kernel support for the Allwinner VPU.

Here are the main highlights of our contributions to Linux 5.0:

After 1.5 years of work, the I3C subsystem was finally merged and visible in drivers/i3c in your favorite kernel tree! We are proud to have pioneered the Linux kernel support for this new MIPI standard, which aims at providing an alternate solution to I2C and SPI, with interesting new features (higher speed, device discovery and enumeration, in-band interrupts, and more). See also our initial blog post about I3C, and our blog post about I3C being upstream.
In the RTC subsystem, Bootlin engineer and RTC kernel maintainer Alexandre Belloni reworked the way nvmem devices are handled, allowing for multiple nvmem devices to be registered for a single RTC as some have both battery-backed RAM and an on-chip EEPROM. devm_rtc_device_register() has been reimplemented to use the new registration path and is now deprecated. Its counterpart, devm_rtc_device_unregister() has been removed.
In the MTD subsystem
- Boris Brezillon contributed a number of patches to the support for raw NAND mainly related to refactoring the subsystem. For example, some of the patches make the ->select_chip() of nand_chip a legacy hook, and removes its implementation from a number of drivers. All those patches do not bring any new feature per-se, but are part of a larger effort to clean up and modernize the MTD subsystem.
- Boris Brezillon also contributed to the SPI NOR support a mechanism to fixup the information provided in the BFPT table of SPI NOR flashes. This is used to ensure that some Macronix SPI NOR flashes are properly recognized as supporting 4-byte opcodes.
Maxime Ripard contributed a number of improvements to the OV5640 camera sensor driver, especially to remove the hardcoded initialization sequence by a much more flexible initialization code, which allowed to support 60fps and more resolutions.
Maxime Ripard extended the PHY subsystem with two new functions, phy_configure() and phy_validate(), which allow to pass configuration details to PHY drivers. This was then used by Maxime to implement MIPI D-PHY drivers, which need a significant number of configuration parameters. See this commit and this commit for details. MIPI D-PHY are typically used in video display or capture HW pipelines.
As part of our work on RaspberryPi display support, Boris Brezillon contributed a number of fixs to the VC4 display controller driver.
For the support of Microchip MPU (Atmel) platforms, Alexandre Belloni migrated the AT91SAM9260, AT91SAM9261, AT91SAM9263, AT91SAM9RL, AT91SAM9x5, SAMA5D2 and SAMA5D4 platforms to the new clock Device Tree binding that he introduced in Linux 4.20.
For the support of Microchip UNG (formerly Microsemi) platforms, Alexandre Belloni added support for the Jaguar2 platform to the pinctrl driver already used for the Ocelot platform.
For the support of Allwinnner platforms:
- Maxime Ripard did a huge amount of Device Tree cleanups and improvements, fixing DTC warnings, but generally making sure those Device Tree files are consistent.
- Paul Kocialkowski implemented support for YUV planes in the Allwinner display controller driver. This allows to display a video decoded by the VPU directly into a display controller plane, and let the hardware compose it with other display planes, without CPU intervention.
- Paul Kocialkowski enabled the VPU (for hardware-accelerated video decoding) on the Allwinner H5 and A64. This work was part of our crowdfunding campaign around the Allwinner VPU support.
For the support of Marvell platforms
- Miquèl Raynal added support for suspend/resume to the SATA support on Armada 3720 (the SoC used for the popular EspressoBin platform), as part of a larger effort of bringing full suspend/resume support on Armada 3720
- Miquèl Raynal implemented support for the thermal overheat interrupt on Armada 7K/8K.

Here is the detailed list of commits we contributed to Linux 5.0:

Bootlin at the Buildroot Developers Meeting, February 2019

Buildroot logo It’s now a tradition: the Buildroot project organizes one of its Buildroot Developers Meeting right after the FOSDEM conference. 2019 was no exception, and the meeting took place from February 4 to February 6, a three days duration, instead of the traditional two days duration from the previous years. Once again, the meeting was sponsored by Google, who provided the meeting location and lunch for all participants. Bootlin participated to the event, by allowing its engineer Thomas Petazzoni to join the meeting.

The meeting was a mix of discussions on various topics and actual hacking, with a focus on reducing the backlog of pending patches. The report synthetizes the most important discussion items:

A short general assembly of the Buildroot Association took place
Some discussions around the download infrastructure took place, related to the re-introduction of the make source-check feature and the issue of tarball reproducibility with version control system download backends
Discussion about introducing Config.in options for all host packages, an idea that we decided to not pursue for the moment.
Discussion about the instrumentation hooks that are used to collect the list of files installed by packages, and how we can achieve this goal in a way that is both efficient and reliable
Discussion on which Qt5 versions to support
Discussion on participating to the Google Summer of Code. We wrote a few topic ideas and applied as an organization for GSoC 2019.
Discussion on how to integrate support for systemd sysusers mechanism

Reading the work on the pending patches, we managed to reduce the backlog from about 300 patches to around 170 patches, which is a very significant achievement.

From left to right: Mark Corbin, Adam Duskett, Angelo Compagnucci (front), Peter Korsgaard (back), Thomas Petazzoni (front), Arnout Vandecappelle (back), Thomas De Schampheleire, Adrian Perez de Castro and Titouan Christophe. Behind the camera: Yann E. Morin.

More specifically, Thomas Petazzoni took advantage of this meeting to:

Finalize his work on the pkg-stats script, to include details about the latest available upstream version of each Buildroot package. To do so, it relies on information provided by the release-monitoring.org website. The information is not yet accurate for all packages, but the accuracy can be improved by contributing to release-monitoring.org. The updated package statistics page now provides those details, which will help ensure Buildroot packages are kept up-to-date.
Review in detail the patch series from Adam Duskett introducing support for GObject Introspection. It is far from a trivial package due to the need to run during the build some small binaries using Qemu. While the series is not merged yet, we have a much better understanding of it, which will help complete the review process.
Do a final review and apply the lengthy patch series reworking the fftw package.
Participate, as a Buildroot co-maintainer, to the pending patches backlog cleanup, by reviewing and/or merging a significant number of patches.

It was once again a very nice and productive meeting. The next meeting will take place as usual around the Embedded Linux Conference Europe, in October, in Lyon (France).

2018 at Bootlin, a year in review

First of all, the entire team at Bootlin wishes you a Happy New Year, and best wishes for 2019 in your personal and professional life. The beginning of the new year is a good time to look back and see the achievements of the past year, which is why we review the 2018 year in terms of Bootlin news and activity:

We’re now called Bootlin
Kernel contributions
U-Boot contributions
Other contributions
Other engineering projects
Conferences
Training
Office expansion
Recruiting
Financial support

We’re now called Bootlin

Due to a legal battle related to trademarks, we decided to change our name to Bootlin at the beginning of 2018. The company was not sold or purchased, it is still owned by the same people, and driven by the same team of engineers. This change of name obviously took a lot of time, which could have been used for other more productive contribution activities, but it’s finally done, and in 2019 we can move on and leave this legal battle behind us. See our blog post for more details.

Kernel contributions

In 2018, we contributed to the 4.15, 4.16, 4.17, 4.18, 4.19 and 4.20 kernel releases a total of 1365 commits, putting Bootlin regularly in the top 20 companies contributing to the Linux kernel.

Our most significant contributions have been:

Thanks to a successful crowdfunding campaign launched in February, we have been able to dedicate enough time to develop and upstream a Linux kernel driver and associated user-space library to support hardware-accelerated video decoding on Allwinner processors. This was a massive effort as it required discussing with the Linux kernel community a new set of userspace interfaces to support stateless video decoders. The base of our driver was merged in Linux 4.20 and supports only MPEG2 decoding. Support for H264 and H265 decoding is ready and has been posted several times, but discussions on the userspace interface are still on-going. See our numerous blog posts and especially the end of year status.
We have developed and contributed a brand new Linux kernel subsystem to support the MIPI I3C bus, a modern bus offering an alternative to SPI or I2C. Being vastly different from I2C, it required a completely separate subsystem located in drivers/i3c/. Along with the core subsystem itself, we developed a driver for the Cadence I3C master, and a driver for a Cadence I3C GPIO expander. See our blog posts on I3C for more details.
We contributed a new interface called exec_op for NAND flash controller drivers, which allows the MTD subsystem to more easily support optimized NAND flash controllers and vendor-specific NAND commands. This new interface was originally developed for the Marvell NAND controller driver, but a number of other drivers have been converted since then, and all new drivers make use of his interface. See our blog post for more details.
We contributed support for the Microsemi VSC7513 and VSC7514 MIPS processors, with the base support (irqchip, pinctrl, gpio, reset, DT) but more importantly a massive switchdev driver to support the major feature of these processors: a built-in gigabit Ethernet switch. Our switchdev driver supports bridging, STP, IGMP snooping, VLAN filtering and link aggregation. See our blog posts about platform support and switchdev support.
We contributed a new subsystem called spi-mem, which allows to support SPI flash memories in a generic way, re-using SPI controller drivers for regular SPI devices, SPI NOR flashes and SPI NAND flashes, instead of having separate controller drivers as was done until now for SPI NOR support. On top of spi-mem, we added support for SPI NAND flash memories to Linux. See our blog post on spi-mem: bringing some consistency to the SPI memory ecosystem.
We contributed a number of drivers for Cadence hardware IPs: Cadence MIPI CSI receiver, Cadence MIPI CSI transceiver, Cadence DSI encoder, Cadence PCIe host controller, Cadence PCIe endpoint controller and as detailed above Cadence I3C master controller.
We continued to work on improving the support for Marvell ARM processors
- Improvements in the inside-secure crypto accelerator driver: support for new crypto algorithms, support for the EIP97 variant which enabled using the driver on Armada 37xx in addition to the already support EIP197 variant used on Armada 7K/8K, numerous fixes and performance improvements
- Improvements in the mvpp2 network controller driver, used on Armada 7K/8K: RSS support, support for SFP ports, HW offloading for VLAN filtering, 1000baseX and 2500baseX support
- On Armada 7K/8K, we added support for the NAND controller and the thermal sensors.
- On Armada 37xx, we added cpufreq support and the first pieces of suspend/resume support.
Allwinner platform support improvements: of course the Allwinner VPU driver detailed above, but also general improvements to the Allwinner A83 support (for which we delivered a complete BSP for a customer), improvements to the sun4i display driver (especially support for YUV planes, and MIPI DSI support on Allwinner A33), improvements to the sun8i-codec audio driver, and improvements to the AXP209 and AXP813 PMIC drivers.
For Microchip/Atmel platforms, we continued our maintenance work, with a focus this year on reworking the representation of the platform clocks in the Device Tree.

U-Boot contributions

Even if Bootlin is mainly active as a Linux kernel contributor, we also contribute to U-Boot, and we have been more active in 2018 than we were in the past. In a recent blog post, we summarized our most significant contributions:

Support for SPI NAND memories, as well as a significant sync of the MTD stack in U-Boot with the one from Linux, and the introduction of a generic mtd U-Boot command to manipulate all types of flash memories
Generic support for TPMv2 and for TPMv2 chips connected over SPI
Brand new subsystem to support 1-wire controllers and devices
Support for the Microsemi Ocelot and Luton MIPS processors. We also contributed support for Microsemi Ocelot to Linux, as discussed above
Support for the ARM PL022 SPI controller
Support for multiple U-Boot environment backends
Support for Microsemi VSC8574 and VSC8584 Ethernet PHYs

In total, we contributed 172 commits to U-Boot in 2018.

Other contributions

Beyond Linux and U-Boot, we also contributed to a few other open-source projects:

We continued to be very active in the Buildroot project, with Bootlin CTO Thomas Petazzoni acting as a co-maintainer of this project. We contributed 431 commits to Buildroot in 2018, but more importantly as a co-maintainer, Thomas reviewed and merged close to 3000 patches in 2018. Thomas also participated to the Buildroot Developers Meeting after FOSDEM, the Buildroot Hackathon, and the Buildroot Developers meeting before ELCE.
We contributed to the Intel GPU Tools project, adding support for testing more pixel formats, to test the display pipeline of the RaspberryPi, in combination with the Chamelium testing hardware. See our blog post and intel-gpu-tools commits
As part of using the Linux Test Project for one of our customers, we contributed a small number of fixes, and we have more to contribute in 2019.
We made our Elixir Cross Referencer project easier to customize, so that contributors can add support for a new source code repository through a single plugin file, instead of having to modify the main source files. Thanks to this, we currently index 8 projects on https://elixir.bootlin.com/.

Other engineering projects

While many of our engineering projects are directly related to upstream contributions, which have been described above, some are not always leading to direct contributions. Here is a small selection of other interesting projects we worked on in 2018:

For a German customer in the healthcare industry, wrote a complete U-Boot, Linux and Buildroot BSP for a custom NXP i.MX6 platform.
For an international company in the TV/set-top box industry, worked on adding support for top-level parallel build to Buildroot.
For a Netherlands based customer in the gaming industry, wrote a complete U-Boot, Linux and Buildrot BSP for a custom Allwinner A33 platform, with significant boot time optimization to quickly boot up to a Qt5 OpenGL application.
For a Spanish customer, brought up a PCM1789 audio codec connected to a NXP i.MX6 processor, and for an Italian customer, brought up a CS4272 audio codec connected to an Allwinner A20 processor. Under Linux, of course!
We continued working for a major US customer, delivering an i.MX6 and SPEAr600 Linux BSP based on Yocto. Our work in 2018 was mainly focused on supporting secure boot on i.MX6 (see our talk at ELC on this topic) and porting a modern version of U-Boot on the SPEAr600 platform.
For a customer in Chile, we worked on supporting a OV5640 camera sensor connected over CSI to an Allwinner H3 platform. Thanks to this, we made a significant number of improvements to the OV5640 driver.
We have continued to maintain toolchains.bootlin.com, by keeping the toolchains reguarly updated, and adding support for the RISC-V 64 bit architecture. See our blog posts.

Conferences

In 2018, Bootlin was at a large number of conferences and events:

At FOSDEM, where Miquèl Raynal gave a talk Drive your NAND within Linux, forget the word “nightmare”. See our blog post
At Embedded Linux Conference, where we gave 5 talks, 2 tutorials and 1 BoF. Talks were related to secure boot, I3C, NAND support, Buildroot and switchdev driver. Tutorials on kernel driver development and Buildroot, and the BoF on system size. See the blog post about our talks and the blog post with our selection of talks from other speakers
At Kernel Recipes, Grégory Clement gave a talk about MMC support in Linux. See our blog post about this event.
At Alpine Linux Persistence and Storage Summit, where Miquèl Raynal and Boris Brezillon gave a talk about their work to bring SPI NAND support to Linux. See our blog post.
Maxime Ripard attended the X.org Developers Conference, see his report from the event.
A large part of the team attended the Embedded Linux Conference Europe, where we gave three talks (support for stateless video codecs in Linux, networking from the MAC to the link partner, SPI memory support in U-Boot and Linux), 2 tutorials (introduction to kernel driver development, introduction to Buildroot) and 2 demonstrations (Allwinner VPU work, and switchdev driver for Microsemi platforms). See our report from the event and our selection of talks from other speakers.
Right next to the Embedded Linux Conference Europe, Maxime Ripard attended the Media Summit to discuss the V4L Linux subsystem, see his report, while Maxime Chevallier attended the Real-Time Summit, see his report.
Antoine Ténart attended the Linux Plumbers conference, see also his report.

Training

In 2018, we gave our Embedded Linux, Linux kernel, Yocto Project and Buildroot training courses on-site in the United States, Portugal, Belgium, Germany, France, Spain, Serbia, Greece, Bosnia, Finland and Switzerland. As you can see, we travel all around the world to teach our training courses.

Of course, we continued our public training sessions organized in Avignon (France), given in English by Bootlin founder and CEO Michael Opdenacker.

In 2018, we made 217 commits to our training materials Git repository, showing our continuous work to keep them updated. Our training materials remain all freely available under a Creative Commons CC-BY-SA license, as they have been since Bootlin creation fifteen years ago.

Office expansion

In 2018, we expanded both our Toulouse and Lyon offices:

We moved our office in Toulouse mid-2018 from a 100m² surface to a 180m² one, offering more room for the existing team, and room to expand the team in the coming years. As of January 1, 2019, we have a team of 8 engineers working in Toulouse.
We moved our office in Lyon end of 2018 from a small one room office of 30m² to a full office of 100m², here as well to expand the team in the coming years. As of January 1, 2019, the team in Lyon has 2 engineers, but we hope to increase this number soon (see Recruiting below).

Recruiting

In terms of recruiting:

Maxime Chevallier joined us in February 2018, and has since then been mostly working on networking topics on Marvell platforms, but also a few other engineering projects.
Paul Kocialkowski joined us in March 2018 for an internship focused on the Allwinner VPU development and then was hired as a full-time engineer starting November 2018.
Thanks to our office expansion in Lyon, we have an open position for a Embedded Linux and Kernel engineer with existing experience in Lyon. See our blog post (in French) for more details.
We have openings for several internships in 2019, on Linux, U-Boot, Buildroot and Elixir related topics. See our blog post (in French).

Financial support

In 2018, we continued to support organizations and events who promote and defend Free Software:

Donating 1,024 EUR to Framasoft, an organization whose goal (in addition to supporting Free Software) is to decentralize Internet services. For example, they made a huge effort to release PeerTube in 2018, a peer-to-peer and of course Free Software alternative to centralized video hosting solutions.

Donating 1,024 EUR to Wikimedia France, to support free knowledge sharing through projects such as Wikipedia and Wikimedia Commons.

Donating 1,024 EUR to April, a French organization doing terrific work to promote Free Software, to follow the evolution of national and European law, and to animate campaigns to keep our political representatives aware of the needs of Free Software developers and users.

We also sponsored the Capitole du Libre 2018 (250 EUR) and Buildroot Developers Meeting 2018 in Edinburgh (250 EUR) events.

And of course, we support the LWN.net on-line weekly column through a corporate subscription (810 USD).

Last words

We have plenty of ideas for 2019, so stay tuned for more news. We hope that 2019 will be a great year for you too, with many contributions of all kinds to the lives of others.

A year of Bootlin contributions to U-Boot

We regularly post about Bootlin contributions to the Linux kernel, but we more rarely post about our U-Boot contributions. Even though we are a bit less active in U-Boot than we are in Linux, we do quite a bit of upstream U-Boot work as well. In this blog post, we do a review of our most significant U-Boot contributions in 2018.

U-Boot 2018.03

Maxime Ripard contributed support for using multiple U-Boot environments. Thanks to this, multiple U-Boot environment backends can be compiled into a single U-Boot binary, so that it can support falling back to a different environment backend if needed. For example, U-Boot can try to load an environment from a file in a FAT partition, and if that fails, try to load from raw MMC storage. As explained by Maxime Ripard in his cover letter, this is useful to help converting Allwinner-based platforms from an environment stored in raw MMC to an environment stored in a FAT partition.

U-Boot 2018.05

Miquèl Raynal contributed support for the Allwinner A33 based Nintendo NES Classic platform. It was also the first Allwinner A33 platform supported in U-Boot that boots from NAND, so as part of this work, Miquèl had to change the Allwinner NAND driver used in the SPL to make it work on Allwinner A31, which required using PIO transfers instead of DMA, and a number of other changes.

U-Boot 2018.07

Miquèl Raynal contributed generic support for TPMv2, and also specifically support for TPMv2 chips over SPI. We will publish a more detailed blog post about this topic in the near future.

U-Boot 2018.09

Quentin Schulz improved the env import command so that it can filter the environment variables it loads from the provided environment. This allows to white-list only a few selected environment variables in cases where the system is locked down by secure boot, but we still need a small writable U-Boot environment to store a few variables. As part of this release, Miquèl Raynal also contributed a few TPM-related fixes.

U-Boot 2018.11

Miquèl Raynal contributed a lot of changes in the MTD subsystem, which brought support for SPI NAND flash memories in U-Boot. We described this work in a previous blog post. Boris Brezillon helped by submitting a number of fixes related to this effort.
Miquèl Raynal contributed a new mtd command, which can be used in a generic way to access all flash memories. This command will replace commands such as sf, nand, etc. We will publish in the near future a separate blog post about this topic.
Quentin Schulz contributed a SPI controller driver for the ARM PL022 SPI controller, which we are using on an old STMicro SPEAr600 platform.
Maxime Ripard contributed a brand new subsystem to support One Wire devices. This work was initially started by Maxime years ago as part of our work on the CHIP platform from Nextthing, and was picked up by Eugen Hristev from Microchip who pushed it all the way to upstream U-Boot.

U-Boot 2019.01

Grégory Clement contributed the support for the Microchip/Microsemi Ocelot and Luton MIPS platforms, which includes the core code, but also a GPIO driver and a pinctrl driver.
Boris Brezillon contributed a number of fixes in the MTD subsystem to address various issues introduced by our work on this subsystem in the previous release.
Quentin Schulz contributed support for the VSC8574 and VSC8584 Ethernet PHYs from Microchip/Microsemi.
Miquèl Raynal improved the NAND controller driver for Marvell platforms by adding raw read support, which was used to add support for NAND chips using 2 KB pages and a ECC strength of 8 bits.

Overall contribution statistics

Overall, during this year, Bootlin engineer Miquèl Raynal contributed 90 commits, Maxime Ripard 33 commits, Boris Brezillon 24 commits, Quentin Schulz 14 commits, Grégory Clement 9 commits and Mylène Josserand 2 commits, a total of 172 commits, including some significant new features: SPI NAND support, TPMv2 support, One Wire subsystem, Ocelot and Luton platform support, ARM PL022 SPI controller support, support for additional Ethernet PHY, support for multiple environments.

We expect to continue our involvement in upstream U-Boot development, starting with a new network driver for the Microchip/Microsemi Ocelot and Luton platforms.

Detailed list of our contributions

Linux 4.20 released, Bootlin contributions

The Linux 4.20 kernel has been released just before Christmas, on December 23. As usual, LWN had a very nice coverage of the most significant features and improvements provided by this new release as part of the merge window articles: part 1 and part 2.

Bootlin once again contributed to this Linux 4.20 release, with a total of 216 non-merge commits, which puts us the 13th contributing company by number of commits and the 8th contributing company by number of lines changed, according to LWN statistics for the 4.20 release.

Significant Bootlin contributions

For Linux 4.20, the most significant contributions from Bootlin have been:

On the support for Marvell platforms
- Antoine Ténart reworked how the “software thread” mechanism is handled in the mvpp2 network driver, used on Marvell Armada 375 and 7K/8K.
- Maxime Chevallier enabled XPS support in the same mvpp2 driver
- Maxime Chevallier added logic to support 2.5G speed in the mvneta driver, but this logic is not enabled yet, as we don’t have the necessary COMPHY driver for Armada 38x to really allow using 2.5G speed.
- Miquèl Raynal added suspend/resume support for the Armada 37xx clock driver. This is part of a larger work to enable suspend/resume on the Armada 37xx platform.
- Miquèl Raynal improved the Marvell ICU driver to support SEI interrupts. The ICU is the Interrupt Collector Unit, found on Marvell Armada 7K/8K. It turns wired interrupts from a part of the chip called the “Communication Processor” (CP) into message interrupts so that they can be notified to the other part of the chip called the “Application Processor” (AP), which contains the CPU core and GIC.
- Thomas Petazzoni introduced some common code in the PCI subsystem to emulate a PCI root port bridge, and converted the pci-mvebu and pci-aardvark drivers to use it. pci-mvebu already had such an emulation logic, but since it became also needed for pci-aardvark, we turn it into a piece of common code so that it can be shared by both drivers (and perhaps others in the future). pci-mvebu is used on Marvell Armada XP, 370, 375, 38x, while pci-aardvark is used on Marvell Armada 37xx.
On the support for Allwinner platforms
- Paul Kocialkowski contributed the Cedrus VPU driver, with for now just MPEG2 decoding support. This work was done thanks to the successful crowd-funding campaign we did in February/March 2018.
- Paul Kocialkowski contributed a few fixes to the sun4i DRM display driver.
On the support for Microchip/Microsemi MIPS platforms
- Alexandre Belloni added support for the Microsemi Jaguar2 in the Designware SPI controller driver
- Alexandre Belloni added support for the Microsemi Ocelot in the Designware I2C controller driver
- Quentin Schulz contributed a new driver in the PHY subsystem to configure the SERDES muxing on Microsemi Ocelot platforms
- Quentin Schulz contributed a new Device Tree description for the Microsemi Ocelot PCB120 platform
On the support Microchip/Atmel ARM platforms
- Alexandre Belloni got the first step of the clock drivers rework merged. The purpose of this rework is to move from a Device Tree representation with one Device Tree node per clock to a much simpler representation with only one Device Tree node for the whole clock controller. The SAMA5D2, SAMA5D4, AT91SAM9260, AT91SAM9x5 at AT91SAM9RL clock drivers have already been converted. Other platforms and DT changes will arrive in future releases.
In the support for RaspberryPi platforms
- Boris Brezillon contributed a few minor fixes for the vc4 DRM driver.
In the RTC subsystem
- As the subsystem maintainer, Alexandre Belloni as usual did a number of cleanups and improvements in numerous drivers, especially to use more modern APIs where possible.
In the network subsystem
- Quentin Schulz contributed extensive support for the Microsemi VSC8574 and VSC8584 Ethernet PHYs.
In the MTD subsystem
- Subsystem maintainer Boris Brezillon did a lot of changes to pass a nand_chip object to numerous NAND subsystem hooks, and fixed all the drivers accordingly.
- Boris Brezillon also deprecated a significant number of NAND subsystem hooks, by introducing a nand_legacy structure with legacy hooks. This should encourage developers to move their drivers to the more modern MTD/NAND APIs.

Bootlin maintainers activity

A number of Bootlin engineers are maintainers in the Linux kernel, so their work is not visible as patch authors, but rather as developers reviewing and merging patches contributed by others. As part of this maintainer work:

Maxime Ripard reviewed and merged 47 patches from other developers, as the Allwinner platform co-maintainer
Boris Brezillon reviewed and merged 36 patches from other developers, as the MTD subsystem co-maintainer
Alexandre Belloni reviewed and merged 64 patches from other developers, as the RTC subsystem maintainer and the Microchip/Atmel platform co-maintainer
Grégory Clement reviewed and merged 25 patches from other developers, as the Marvell platform co-maintainer
Miquèl Raynal reviewed and merged 71 patches from other developers, as the NAND subsystem co-maintainer

Detailed list of Bootlin contributions

MIPI I3C support is now in upstream Linux

MIPI I3C specification published Back in August 2017, we wrote in a blog post about the first iteration of the Linux kernel subsystem we proposed to support the brand new MIPI I3C bus. Almost a year and half later, there are some really good news:

The Linux I3C support now has its own Git repository on kernel.org
The Linux I3C community has its mailing list.
Besides the first I3C controller driver we wrote for the Cadence I3C Master, Synopsys has contributed a second driver for their I3C master IP: i3c: master: Add driver for Synopsys DesignWare IP. This definitely helped show that there is interest in I3C beyond our contributions, and also helped validate that the subsystem was working fine for a different I3C controller.
The Linux I3C tree has been part of linux-next since November 6, 2018: linux-next: Tree for Nov 6.
The Linux I3C subsystem has received a Reviewed-by: Arnd Bergmann and later on a Acked-by: Greg Kroah-Hartman, which were two key approvals to move forward with the merging of I3C support.
I3C subsystem maintainer Boris Brezillon has therefore sent a pull request to get this subsystem merged in the upcoming 4.21 (or 5.0 ?) Linux kernel: [GIT PULL] i3c: Initial pull request, and this pull request has been merged by Linus Torvalds, so the I3C subsystem is now visible in Linus Git tree: drivers/i3c. The merge commit has been done on December 25, so it arrived as a very nice Christmas present!

It has been a long process, but we are proud and happy to have pioneered the support for I3C in the Linux kernel, from the design of the subsystem based on the I3C specifications all the way to its merging in the upstream Linux kernel and the creation of a small (but hopefully growing) community of developers around it.