Bootlin engineer Boris Brezillon becomes Linux NAND subsystem maintainer

Bootlin engineer Boris Brezillon has been involved in the support for NAND flashes in the Linux kernel for quite some time. He is the author of the NAND driver for the Allwinner ARM processors, did several improvements to the NAND GPMI controller driver, has initiated a significant rework of the NAND subsystem, and is working on supporting MLC NANDs. Boris is also very active on the linux-mtd mailing list by reviewing patches from others, and making suggestions.

Hynix NAND flash

For those reasons, Boris was recently appointed by the MTD maintainer Brian Norris as a new maintainer of the NAND subsystem. NAND is considered a sub-subsystem of the MTD subsystem, and as such, Boris will be sending pull requests to Brian, who in turn is sending pull requests to Linus Torvalds. See this commit for the addition of Boris as a NAND maintainer in the MAINTAINERS file. Boris will therefore be in charge of reviewing and merging all the patches touching drivers/mtd/nand/, which consist mainly of NAND drivers. Boris has created a nand/next branch on Github, where he has already merged a number of patches that will be pushed to Brian Norris during the 4.7 merge window.

We are happy to see one of our engineers taking another position as a maintainer in the kernel community. Maxime Ripard was already a co-maintainer of the Allwinner ARM platform support, Alexandre Belloni a co-maintainer of the RTC subsystem and Atmel ARM platform support, Grégory Clement a co-maintainer of the Marvell EBU platform support, and Antoine Ténart a co-maintainer of the Annapurna Labs platform support.

Bootlin contributions to Linux 4.5

Adelie PenguinLinus Torvalds just released Linux 4.5, for which the major new features have been described by LWN.net in three articles: part 1, part 2 and part 3. On a total of 12080 commits, Bootlin contributed 121 patches, almost exactly 1% of the total. Due to its large number of contribution by patch number, Bootlin engineer Boris Brezillon appears in the statistics of top-contributors for the 4.5 kernel in the LWN.net statistics article.

This time around, our important contributions were:

  • Addition of a driver for the Microcrystal rv1805 RTC, by Alexandre Belloni.
  • A huge number of patches touching all NAND controller drivers and the MTD subsystem, from Boris Brezillon. They are the first step of a more general rework of how NAND controllers and NAND chips are handled in the Linux kernel. As Boris explains in the cover letter, his series aims at clarifying the relationship between the mtd and nand_chip structures and hiding NAND framework internals to NAND. […]. This allows removal of some of the boilerplate code done in all NAND controller drivers, but most importantly, it unifies a bit the way NAND chip structures are instantiated.
  • On the support for the Marvell ARM processors:
    • In the mvneta networking driver (used on Armada 370, XP, 38x and soon on Armada 3700): addition of naive RSS support with per-CPU queues, configure XPS support, numerous fixes for potential race conditions.
    • Fix in the Marvell CESA driver
    • Misc improvements to the mv_xor driver for the Marvell XOR engines.
    • After four years of development the 32-bits Marvell EBU platform support is now pretty mature and the majority of patches for this platform now are improvements of existing drivers or bug fixes rather than new hardware support. Of course, the support for the 64-bits Marvell EBU platform has just started, and will require a significant number of patches and contributions to be fully supported upstream, which is an on-going effort.
  • On the support for the Atmel ARM processors:
    • Addition of the support for the L+G VInCo platform.
    • Improvement to the macb network driver to reset the PHY using a GPIO.
    • Fix Ethernet PHY issues on Atmel SAMA5D4
  • On the support for Allwinner ARM processors:
    • Implement audio capture in the sun4i audio driver.
    • Add the support for a special pin controller available on Allwinner A80.

The complete list of our contributions:

Bootlin contributing Linux kernel initial support for Annapurna Labs ARM64 Platform-on-Chip

Annapurna Labs LogoWe are happy to announce that on February 8th 2016 we submitted to the mainline Linux kernel the initial support for Annapurna Labs Alpine v2 Platform-on-Chip based on the 64-bit ARMv8 architecture.

See our patch series:

Annapurna Labs was founded in 2011 in Israel. Annapurna Labs provides 32-bit and 64-bit ARM products including chips and subsystems under the Alpine brand for the home NAS, Gateway and WiFi router equipment, see this page for details. The 32-bit version already has support in the official Linux kernel (see alpine.dtsi), and we have started to add support for the quad core 64-bit version, called Alpine v2, which brings significant performance for the home.

This is our initial contribution and we plan to follow it with additional Alpine v2 functionality in the near future.

Bootlin at the Embedded Linux Conference 2016

Like every year for about 10 years, the entire Bootlin engineering team will participate to the next Embedded Linux Conference, taking place on April 4-6 in San Diego, California. For us, participating to such conferences is very important, as it allows to remain up to date with the latest developments in the embedded Linux world, create contacts with other members of the embedded Linux community, and meet the community members we already know and work with on a daily basis via the mailing lists or IRC.

Embedded Linux Conference 2016

Over the years, our engineering team has grown, and with the arrival of two more engineers on March 14, our engineering team now gathers 9 persons, all of whom are going to participate to the Embedded Linux Conference.

As usual, in addition to attending, we also proposed a number of talks, and some of them have been accepted and are visible in the conference schedule:

As usual, our talks are centered around our areas of expertise: hardware support in the Linux kernel, especially for ARM platforms, and build system related topics (Buildroot, Yocto, autotools).

We are looking forward to attending this event, and see many other talks from various speakers: the proposed schedule contains a wide range of topics, many of which look really interesting!

Bootlin speaking at the Linux Collaboration Summit

Bootlin engineers are regular speakers at the Embedded Linux Conference and Embedded Linux Conference Europe events from the Linux Foundation, to which our entire engineering team participates each year.

In 2016, for the first time, we will also be speaking at the Collaboration Summit, an invitation-only event where, as the Linux Foundation presents it, “the world’s thought leaders in open source software and collaborative development convene to share best practices and learn how to manage the largest shared technology investments of our time”.

Collaboration Summit 2016

This event will take place on March 29-31 in Lake Tahoe, California, and the event schedule has been published recently. Bootlin CTO Thomas Petazzoni will be giving a talk Upstreaming hardware support in the Linux kernel: why and how?, during which we will share our experience working with HW manufacturers to bring the support for their hardware to the upstream Linux kernel, discuss the benefits of upstreaming, and best practices to work with upstream.

With a small team of engineers, Bootlin has merged over the last few years thousands of patches in the official Linux kernel, and has several of its engineers having maintainer positions in the Linux kernel community. We are happy to take the opportunity of the Collaboration Summit to share some of our experience, and hopefully encourage and help other companies to participate upstream.

Bootlin contributes Linux support for a first ARM64 platform: Marvell Armada 3700

Marvell Armada 3700Over the last years, Bootlin has become a strong participant to the Linux ARM kernel community, with our engineers upstreaming support for numerous ARM 32 bits platforms.

Now, with ARM64 becoming more and more mainstream, our focus in 2016 will shift towards this architecture, and we’re happy to announce that we have recently contributed to the upstream Linux kernel the initial support for our first ARM64 architecture: the Marvell Armada 3700.

This new SoC from Marvell is available in single-core and dual-core Cortex-A53 configurations, and features a wide range of peripherals: 2 Gigabit Ethernet controllers, USB 3.0 and 2.0, SATA, PCIe interfaces, DMA engines for XOR acceleration, and of course the usual SPI, I2C, UART, GPIO, SDIO interfaces. For more details, see the Product Brief.

So far, we have sent a patch series adding minimal support for this platform:

  • A UART driver, since this SoC uses a new specific UART controller
  • Small changes to an AHCI driver to support SATA.
  • The Device Tree files describing the SoC and the currently available development board. So far, only the CPU, timers, UART0, USB 3.0, SATA and GIC interrupt controllers are described.

A second version of the patch series was sent a few days later, in order to address comments received during the review.

It is worth mentioning that this SoC was publicly announced in a press release on January 6 2016, and we’ve been able to send the initial support patches on February 2, 2016, less than a month later.

We’ll be progressively submitting support for all the other hardware blocks of the Armada 3700, and also be announcing soon our development efforts on several other ARM64 platforms.

2016 Q1 newsletter

Newsletter iconThe 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:

Contact us at training@bootlin.com for details.

Conferences

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

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

Porting Linux on an ARM boardOn 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 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:

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: