Linux 4.20 released, Bootlin contributions

Penguin from Mylène Josserand
Drawing from Mylène Josserand, based on a picture from Samuel Blanc (
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

Author: Thomas Petazzoni

Thomas Petazzoni is CTO and embedded Linux and kernel engineer at Bootlin. He is a lead developer of Buildroot and also a contributor to the Linux kernel. More details...

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