Linux 4.8 released, Bootlin contributions

Adelie PenguinLinux 4.8 has been released on Sunday by Linus Torvalds, with numerous new features and improvements that have been described in details on LWN: part 1, part 2 and part 3. KernelNewbies also has an updated page on the 4.8 release. We contributed a total of 153 patches to this release. LWN also published some statistics about this development cycle.

Our most significant contributions:

  • Boris Brezillon improved the Rockchip PWM driver to avoid glitches basing that work on his previous improvement to the PWM subsystem already merged in the kernel. He also fixed a few issues and shortcomings in the pwm regulator driver. This is finishing his work on the Rockchip based Chromebook platforms where a PWM is used for a regulator.
  • While working on the driver for the sii902x HDMI transceiver, Boris Brezillon did a cleanup of many DRM drivers. Those drivers were open coding the encoder selection. This is now done in the core DRM subsystem.
  • On the support of Atmel platforms
    • Alexandre Belloni cleaned up the existing board device trees, removing unused clock definitions and starting to remove warnings when compiling with the Device Tree Compiler (dtc).
  • On the support of Allwinner platforms
    • Maxime Ripard contributed a brand new infrastructure, named sunxi-ng, to manage the clocks of the Allwinner platforms, fixing shortcomings of the Device Tree representation used by the existing implementation. He moved the support of the Allwinner H3 clocks to this new infrastructure.
    • Maxime also developed a driver for the Allwinner A10 Digital Audio controller, bringing audio support to this platform.
    • Boris Brezillon improved the Allwinner NAND controller driver to support DMA assisted operations, which brings a very nice speed-up to throughput on platforms using NAND flashes as the storage, which is the case of Nextthing’s C.H.I.P.
    • Quentin Schulz added support for the Allwinner R16 EVB (Parrot) board.
  • On the support of Marvell platforms
    • Grégory Clément added multiple clock definitions for the Armada 37xx series of SoCs.
    • He also corrected a few issues with the I/O coherency on some Marvell SoCs
    • Romain Perier worked on the Marvell CESA cryptography driver, bringing significant performance improvements, especially for dmcrypt usage. This driver is used on numerous Marvell platforms: Orion, Kirkwood, Armada 370, XP, 375 and 38x.
    • Thomas Petazzoni submitted a driver for the Aardvark PCI host controller present in the Armada 3700, enabling PCI support for this platform.
    • Thomas also added a driver for the new XOR engine found in the Armada 7K and Armada 8K families

Here are in details, the different contributions we made to this release:

Linux 4.7 released, Bootlin contributions

Adelie PenguinLinux 4.7 has been released on Sunday by Linus Torvalds, with numerous new features and improvements that have been described in details on LWN: part 1, part 2 and part 3. KernelNewbies also has an updated page on the 4.7 release. We contributed a total of 222 patches to this release.

Our most significant contributions:

  • Boris Brezillon has contributed a core improvement to the PWM subsystem: a mechanism that allows to update the properties of a PWM in an atomic fashion. This is needed when a PWM has been initialized by the bootloader, and the kernel needs to take over without changing the properties of the PWM. See the main patch for more details. What prompted the creation of this patch series is a problem on Rockchip based Chromebook platforms where a PWM is used for a regulator, and the PWM properties need to be preserved across the bootloader to kernel transition. In addition to the changes of the core infrastructure, Boris contributed numerous patches to fix existing PWM users.
  • In the MTD subsystem, Boris Brezillon continued his cleanup efforts
    • Use the common Device Tree parsing code provided by nand_scan_ident() in more drivers, rather than driver-specific code.
    • Move drivers to expose their ECC/OOB layout information using the mtd_ooblayout_ops structure, and use the corresponding helper functions where appropriate. This change will allow a more flexible description of the ECC and OOB layout.
    • Document the Device Tree binding that should now be used for all NAND controllers / NAND chip, with a clear separation between the NAND controller and the NAND chip. See this commit for more details.
  • In the RTC subsystem, Mylène Josserand contributed numerous improvements to the rv3029 and m41t80 drivers, including the addition of the support for the RV3049 (the SPI variant of RV3029). See also our previous blog post on the support of Microcrystal’s RTCs/.
  • On the support of Atmel platforms
    • Boris Brezillon contributed a number of fixes and improvements to the atmel-hlcdc driver, the DRM/KMS driver for Atmel platforms
  • On the support of Allwinner platforms
    • Maxime Ripard contributed a brand new DRM/KMS driver to support the display controller found on several Allwinner platforms, with a specific focus on Allwinner A10. This new driver allows to have proper graphics support in the Nextthing Co. C.H.I.P platform, including composite output and RGB output for LCD panels. To this effect, in addition to the driver itself, numerous clock patches and Device Tree patches were made.
    • Boris Brezillon contributed a large number of improvements to the NAND controller driver used on Allwinner platforms, including performance improvements.
    • Quentin Schulz made his first kernel contribution by sending a patch fixing the error handling in a PHY USB driver used by Allwinner platforms.
  • On the support of Marvell platforms
    • Grégory Clement made some contributions to the mv_xor driver to make it 64-bits ready, as the same XOR engine is used on Armada 3700, a Cortex-A53 based SoC. Grégory then enabled the use of the XOR engines on this platform by updating the corresponding Device Tree.
    • Romain Perier did some minor updates related to the Marvell cryptographic engine support. Many more updates will be present in the upcoming 4.8, including significant performance improvements.
    • Thomas Petazzoni contributed some various fixes (cryptographic engine usage on some Armada 38x boards, HW I/O coherency related fixes).
    • Thomas also improved the support for Armada 7K and 8K, with the description of more hardware blocks, and updates to drivers.

Here are in details, the different contributions we made to this release:

Linux 4.6 released, with Bootlin contributions

Adelie PenguinThe 4.6 version of the Linux kernel was released last Sunday by Linus Torvalds. As usual, LWN.net had a very nice coverage of this development cycle merge window, highlighting the most significant changes and improvements: part 1, part 2 and part 3. KernelNewbies is now active again, and has a very detailed page about this release.

On a total of 13517 non-merge commits, Bootlin contributed for this release a total of 107 non-merge commits, a number slightly lower than our past contributions for previous kernel releases. That being said, there are still a few interesting contributions in those 107 patches. We are particular happy to see patches from all our eight engineers in this release, including from Mylène Josserand and Romain Perier, who just joined us mid-March! We also already have 194 patches lined-up for the next 4.7 release.

Here are the highlights of our contributions to the 4.6 release:

  • Atmel ARM processors support
    • Alexandre Belloni and Boris Brezillon contributed a number of patches to improve and cleanup the support for the PMC (Power Management and Clocks) hardware block. As expected, this involved patching both clock drivers and power management code for the Atmel platforms.
  • Annapurna Labs Alpine platforms support
    • As a newly appointed maintainer of the Annapurna Labs ARM/ARM64 Alpine platforms, Antoine Ténart contributed the base support for the ARM64 Alpine v2 platform: base platform support and Device Tree, and an interrupt controller driver to support MSI-X
  • Marvell ARM processors support
    • Grégory Clement added initial support for the Armada 3700, a new Cortex-A53 based ARM64 SoC from Marvell, as well as a first development board using this SoC. So far, the supported features are: UART, USB and SATA (as well as of course timers and interrupts).
    • Thomas Petazzoni added initial support for the Armada 7K/8K, a new Cortex-A72 based ARM64 SoC from Marvell, as well as a first development board using this SoC. So far, UART, I2C, SPI are supported. However, due to the lack of clock drivers, this initial support can’t be booted yet, the clock drivers and additional support is on its way to 4.7.
    • Thomas Petazzoni contributed an interrupt controller driver for the ODMI interrupt controller found in the Armada 7K/8K SoC.
    • Grégory Clement and Thomas Petazzoni did a few improvements to the support of Armada 38x. Thomas added support for the NAND flash used on Armada 370 DB and Armada XP DB.
    • Boris Brezillon contributed a number of fixes to the Marvell CESA driver, which is used to control the cryptographic engine found in most Marvell EBU processors.
    • Thomas Petazzoni contributed improvements to the irq-armada-370-xp interrupt controller driver, to use the new generic MSI infrastructure.
  • Allwinner ARM processors support
    • Maxime Ripard contributed a few improvements to Allwinner clock drivers, and a few other fixes.
  • MTD and NAND flash subsystem
    • As a maintainer of the NAND subsystem, Boris Brezillon did a number of contributions in this area. Most notably, he added support for the randomizer feature to the Allwinner NAND driver as well as related core NAND subsystem changes. This change is needed to support MLC NANDs on Allwinner platforms. He also contributed several patches to continue clean up and improve the NAND subsystem.
    • Thomas Petazzoni fixed an issue in the pxa3xx_nand driver used on Marvell EBU platforms that prevented using some of the ECC configurations (such as 8 bits BCH ECC on 4 KB pages). He also contributed minor improvements to the generic NAND code.
  • Networking subsystem
    • Grégory Clement contributed an extension to the core networking subsystem that allows to take advantage of hardware capable of doing HW-controlled buffer management. This new extension is used by the mvneta network driver, useful for several Marvell EBU platforms. We expect to extend this mechanism further in the future, in order to take advantage of additional hardware capabilities.
  • RTC subsystem
    • As a maintainer of the RTC subsystem, Alexandre Belloni did a number of fixes and improvements in various RTC drivers.
    • Mylène Josserand contributed a few improvements to the abx80x RTC driver.
  • Altera NIOSII support
    • Romain Perier contributed two patches to fix issues in the kernel running on the Altera NIOSII architecture. The first one, covered in a previous blog post, fixed the NIOSII-specific memset() implementation. The other patch fixes a problem in the generic futex code.

In addition, several our of engineers are maintainers of various platforms or subsystems, so they do a lot of work reviewing and merging the contributions from other kernel developers. This effort can be measured by looking at the number of patches on which they Signed-off-by, but for which they are not the author. Here are the number of patches that our engineered Signed-off-by, but for which they were not the author:

  • Alexandre Belloni, as the RTC subsystem maintainer and the Atmel ARM co-maintainer: 91 patches
  • Maxime Ripard, as the Allwinner ARM co-maintainer: 65 patches
  • Grégory Clement, as the Marvell EBU ARM co-maintainer: 45 patches
  • Thomas Petazzoni, simply resubmitting patches from others: 2 patches

Here is the detailed list of our contributions to the 4.6 kernel release:

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.