The LinuxCon North America conference was held a few days ago in Chicago.
A number of slides from the conference have been published. While the conference is a general purpose Linux conference, there were quite a few talks discussed kernel or low-level related topics that may be of interest to embedded Linux developers. Amongst them, we noted:
Not all the slides have been posted yet, so be sure to check the slides page regularly for updates!
Linus Torvalds has released the 3.16 kernel a few weeks ago. Unfortunately, the KernelNewbies LinuxChanges page has not been updated, but LWN.net summaries of the merge window (part 1, part 2 and final part) give a good summary of the important changes available in Linux 3.16.
On Free Electrons’ side, 3.16 has been our most active kernel cycle ever: we have merged 388 patches in this cycle, making Free Electrons the 7th company contributing to the Linux kernel by number of patches according to the statistics. Free Electrons is ranked right after Texas Instruments, and before Novell, Renesas or Google. (Note that the statistics rank Free Electrons as 9th, but this includes the “Unknown” and “Hobbyists” categories which are not companies). This strong participation clearly shows Free Electrons’ ability to get code merged in the mainline Linux kernel, as we’ve progressively done since kernel 3.6 over the last two years.
We are therefore available to help companies willing to add support for their hardware (processor, system-on-chip, module, or board) to the mainline Linux kernel. Do not hesitate to contact to get the discussion started.
Our major contributions have again been focused on the support of various ARM processor families:
- On the Atmel SoC family
- Conversion of the SAM9RL processor to the Device Tree. Done by Alexandre Belloni.
- Huge cleanup of ADC/touchscreen handling: improvements in the IIO
at91_adc driver to support more SoC families, and conversions of several Atmel platforms to use this driver, and then finally removal of the old
atmel_tsadcc driver. Done by Alexandre Belloni.
- Numerous fixes to the clock handling on various SoCs, following their conversion to the Common Clock Framework. Done by Alexandre Belloni.
- Conversion of the SAM9RL, SAM9x5 and SAM9n12 SoCs to the Common Clock Framework. Done by Boris Brezillon.
- Boris Brezillon is now one of the official maintainers for AT91 clock support.
- On the Allwinner SoC family
- Addition of PWM support to sun4i and sun7i. Done by Alexandre Belloni.
- Addition of SMBus support to the regmap subsystem. This was needed to support the P2WI bus of Allwinner A31. Done by Boris Brezillon.
- New I2C driver for the P2WI bus of Allwinner A31, used to communicate with the PMIC. Done by Boris Brezillon.
- Improvements to the Allwinner pinctrl driver needed to support the P2WI bus. Done by Boris Brezillon.
- Addition of a driver for the PRCM (Power, Reset and Clock Management) unit of the Allwinner A31. Done by Boris Brezillon.
- Numerous cleanups of the pinctrl driver for Allwinner. Done by Maxime Ripard.
- Addition of the ARM PMU description in the Device Tree of Allwinner platforms. Done by Maxime Ripard.
- Add USB support for Allwinner A31. Done by Maxime Ripard, with some help from Boris Brezillon.
- Various improvements to Allwinner clock drivers. Done by Maxime Ripard.
- On the Marvell Berlin SoC family
- Addition of basic Device Tree descriptions for several Marvell Berlin processors and boards. Done by Antoine Ténart.
- Addition of clock drivers and DT clock descriptions of the Marvell Berlin processors. Done by Alexandre Belloni.
- Addition of the pinctrl drivers for the Marvell Berlin processors. Done by Antoine Ténart.
- Enabling of SDHCI and GPIO support on Marvell Berlin. Done by Antoine Ténart.
- On the Marvell EBU SoC family
- Addition of watchdog support for Armada 375 and Armada 38x, which required some changes to the existing watchdog driver. Done by Ezequiel Garcia.
- Addition of thermal support for Armada 375 and Armada 38x, which required some changes in the existing
armada_thermal driver. Done by Ezequiel Garcia.
- Improvements of the
pxa3xx_nand driver used for NAND support on Armada 370/375/38x/XP to use the newly introduced ECC strength and step size Device Tree bindings, which allows from the Device Tree to override the ECC constraints described by ONFI, when needed to match the bootloader constraints. Done by Ezequiel Garcia.
- Addition of a generic software TSO (TCP Segmentation Offload) layer, and the corresponding changes to enable this feature in the
mvneta network drivers. This gives a huge performance boost in transmit operations! Done by Ezequiel Garcia.
- SMP support for Armada 375 and Armada 38x has been added. Done by Grégory Clement.
- cpuidle support for Armada XP has been added. Done by Grégory Clement.
- USB support (USB2 and USB3) for Armada 375 and Armada 38x has been added. Done by Grégory Clement.
- Hardware I/O coherency support for Armada 375 and Armada 38x. Done by Thomas Petazzoni.
- Enabling of the SDHCI and AHCI interfaces on Armada 38x. Done by Thomas Petazzoni.
- Major clean-up of Marvell Orion5x support. This is an older ARMv5 family of processors from Marvell, having a lot of similarities with Kirkwood and more recent Armada. This cleanup include many Device Tree conversions, up to the point where a few Marvell Orion5x platforms can now be fully described using a Device Tree, with no board file. Done by Thomas Petazzoni.
- Addition of a new Device Tree binding for fixed network links, i.e links that do not use a MDIO-controlled PHY. This involved both some generic PHY layer improvements, and corresponding changes in the Marvell-specific mvneta network driver. Done by Thomas Petazzoni.
- Addition of a work-around for a relatively complex PCIe/L2 errata affecting Armada 375/38x, which fixes heavy PCIe traffic when the system is running with hardware I/O coherency enabled. Done by Thomas Petazzoni.
Here is the complete list of patches from Free Electrons merged into the 3.16 kernel:
- Alexandre Belloni (54 commits)
- Antoine Tenart (16 commits)
- Antoine Ténart (4 commits)
- Boris BREZILLON (50 commits)
- Ezequiel Garcia (64 commits)
- Gregory CLEMENT (36 commits)
- Maxime Ripard (64 commits)
- Thomas Petazzoni (100 commits)
A bit more than a month after publishing the datasheet of the Armada 370 processor, Marvell has now released a similar datasheet for the more powerful Armada XP processor. The datasheet is available as a PDF document, with no registration, at http://www.marvell.com/embedded-processors/armada-xp/assets/ARMADA-XP-Functional-SpecDatasheet.pdf, with a link to it clearly visible on the Armada XP product page.
As most of our readers probably know, Free Electrons has been working and continues to work significantly on the Linux kernel support for Marvell processors. Thanks to this work done for more than two years now, the mainline Linux kernel has pretty good support for the Armada XP processor. This processor is a nice monster: up to 4 cores (PJ4B cores, which are roughly equivalent to Cortex-A9 but with LPAE support), up to 10 PCIe interfaces, multiple SATA interfaces, up to four Gigabit network interfaces, and many, many other things (XOR engine, cryptographic engine, etc.). Many of the processor features are already supported in mainline, and lately we’ve been focusing on power management features: cpuidle support for Armada XP will be part of 3.16, cpufreq support will either be part of 3.17 or 3.18, and suspend/resume should hopefully be part of 3.18.
The Armada XP processor is used in publicly available products:
At Free Electrons, we are again really happy to see Marvell opening this datasheet, as it will allow all community developers to further improve support for this processor in the Linux kernel, but also in other open-source projects.
The 3.15 of the Linux kernel was released just a few days ago by Linus Torvalds. As explained by LWN.net, the headline features in 3.15 include some significant memory management improvements, the renameat2() system call, file-private POSIX locks, a new device mapper target called dm-era, faster resume from suspend, and more. One can also read the coverage by LWN.net of the first part and the second part of the merge window to get more details about the major new features in this release.
As usual, Free Electrons contributed to the Linux kernel during this 3.15 cycle, and with a total of 218 patches contributed, it’s a new record for Free Electrons. According to the KPS statistics, Free Electrons ranked #12 in the list of companies contributing to the Linux kernel for the 3.15 kernel (if you exclude the “Unknown” and “Hobbyists” categories, which aren’t really companies).
The main features contributed by Free Electrons again centered around the support for ARM processors:
- By far, the largest contribution this cycle was the initial support for the new Armada 375 and Armada 38x processors from Marvell. Gregory Clement, Ezequiel Garcia and Thomas Petazzoni have been working on the code to support these processors since a few months ago, and started pushing the patches to the public in February this year. For the Marvell Armada 38x processor, it means that the code was pushed in mainline even before the processor was announced publicly! The features supported in 3.15 for these processors are: interrupts, GPIO, clocks, pin-muxing, serial, I2C, SPI, timer, L2 cache, SDIO (only for 375), SATA (only 375), XOR, PCIe, MBus, networking (only for 38x), NOR and NAND support. Many other features such as SMP, I/O coherency and various other peripherals will be supported in 3.16.
- Convert support for the Atmel AT91SAM9RL processor to the Device Tree, done by Alexandre Belloni.
- Addition of iio-hwmon to the Freescale i.MX23 and i.MX28 processors, which allows to use the internal temperature sensor of the processor. Done by Alexandre Belloni.
- Multiple fixes and improvements to the AT91 ADC support. Done by Alexandre Belloni.
- Support for the watchdog in Armada 370 and Armada XP was added, done by Ezequiel Garcia.
- A driver for the SPI controller found in Allwinner A31 SoC was added, as well as all the Device Tree information to describe this controller and related clocks. Done by Maxime Ripard.
- Support for the I2C controller found in the Allwinner A31 SoC was added into the existing mv64xxx-i2c driver, as well as the necessary Device Tree information to use I2C on this SoC. Done by Maxime Ripard.
- Audio support was enabled on the Armada 370 SoC, re-using existing code for Kirkwood, and therefore making audio work on the Armada 370 DB platform. Done by Thomas Petazzoni.
- A number of issues in the PCIe support for Marvell processors have been fixed, thanks to the reports from a number of users. Done by Thomas Petazzoni, with help from these users.
We also contributed other things than just support for ARM processors:
- The main contribution in this area is the addition of UBI block, a driver that allows to use read-only block filesystems such as squashfs on top of a UBI volume. The code was originally written by David Wagner who was an intern at Free Electrons, and later taken by Ezequiel Garcia who did a lot of additional cleanup work and community discussion to get the driver merged. Some details about this feature can be found in the Linux-MTD documentation.
- A generic Device Tree binding to express NAND ECC related information in the Device Tree was contributed by Ezequiel Garcia.
- The quest to remove
IRQF_DISABLED continued, by Michael Opdenacker.
In details, all our contributions are:
- Alexandre Belloni (35):
- Antoine Ténart (1):
- Ezequiel Garcia (43):
- Gregory CLEMENT (12):
- Maxime Ripard (43):
- Michael Opdenacker (19):
- Thomas Petazzoni (65):
Over the last two years, Free Electrons has contributed support for the Marvell Armada 370 and Marvell Armada XP processors to the mainline Linux kernel. These ARM processors are used mainly in Network Attached Storage devices but also in other devices such as printers. Until now the datasheet for these processors was only available for Marvell customers and partners under NDA, but last week, Marvell finally released the datasheet of the Armada 370 publicly, with no restriction, no registration, no NDA. The Armada 370 processor can already be found in several consumer grade products:
From now on, on the Marvell page related to the Armada 3xx family, the Armada 370 Functional Specification as well as the Armada 370 Hardware Specifications can be found. While the Armada XP datasheet is not available at this time, it is worth mentioning that the vast majority of the peripherals are exactly the same between Armada 370 and Armada XP, so even Armada XP users will find useful information in this datasheet.
Free Electrons is happy to see that Marvell is making more and more progress towards mainlining their kernel support and opening their datasheets publicly. We strongly believe that the openness of these datasheets will allow hobbyists and developers to improve the support for Armada 370 in the open-source ecosystem, be it in the Linux kernel, in bootloaders like U-Boot or Barebox or even in other projects.