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Project crowdfunds effort to bring Allwinner VPU support to the Linux kernel

Feb 9, 2018 — by Eric Brown — 1135 views

Free Electrons changed its name to Bootlin, and funded a Kickstarter campaign to bring support for the Allwinner VPU to the Linux kernel, building upon earlier work done in collaboration with the Linux Sunxi community called sunxi-cedrus.

It’s been a long hard slog to improve Linux support on Allwinner’s ARM-based SoCs, and now a French development firm called Bootlin wants to plug in the last piece of the puzzle. Bootlin has successfully crowdfunded a project to upstream support for the Allwinner video processing unit (VPU) into the Linux kernel. Over $30,000 has been raised on Kickstarter — well over the $21,566 goal — and there are 37 days left to expand the project on its way to a completion goal of June.

Until a week ago, Bootlin was called Free Electrons, a development and training company that has long been at the center of embedded Linux development, including projects such as the Buildroot upstream project. Free Electrons ran afoul of a trademark infringement suit from French telecom firm FREE SAS, and was forced to change its name to Bootlin. FREE SAS has filed more than 100 oppositions and District Court actions against trademarks or names containing the word “free”. The lawsuit is still pending, but Free Electrons decided to avoid a long legal battle by changing its name.


Bootlin logo

In recent years, Free Electrons’ Maxime Ripard and others have collaborated with Next Thing to improve Linux support for Allwinner chips. (Ripard is leading the VPU effort along with Paul Kocialkowski.) Much of the Allwinner Linux work has been done by the Linux Sunxi open source community, which stepped in to do the work that Allwinner should have done in the first place. Linux Sunxi developers have more recently worked to reverse engineer the closed-source binary VPU blob in Allwinner’s Linux BSP in a reverse engineering project known as libvdpau-sunxi.

Bootlin decided to work instead on the similar sunxi-cedrus solution that it launched in 2017, which comprises a Linux kernel driver working on a recent upstream Linux kernel, as well as a libva backend. (See farther below for a video of sunxi-cedrus running on Next Thing’s Chip SBC.)


Chip

Bootlin claims sunxi-cedrus is superior to Linux Sunxi’s libvdpau-sunxi, which it says is designed for an older Allwinner kernel. Sunxi-cedrus also has the advantage of using a standard V4L driver, “which will use a standardized and upstream acceptable user-space API,” says the company. “This will allow the V4L kernel driver to be accepted in the official Linux kernel, ensuring its long-term availability and maintenance.”

Sunxi-cedrus currently supports MPEG2 decoding, and has partial support for MPEG4 decoding. It has been tested on the single-core, Cortex-A8 Allwinner A13 — the original model for the cheaper, more open spec Allwinner R8 used on Next Thing’s Chip SBC. It also works on the quad-core -A7 Allwinner A33, found on boards such as Olimex’s A33-OlinuXino.



Allwinner R8 block diagram
(click image to enlarge)

Bootlin plans to improve the MPEG2 support and extend sunxi-cedrus to support H.264 decoding. It has already achieved the first stretch goal, which is to extend support to newer Allwinner SoCs like the H3, H5, and A64. It’s halfway toward the stretch goal of adding H265 decoding support. A final stretch goal is to add H.264 video encoding.



Bootlin video of sunxi-cedrus running on Chip SBC

 
Further information

Bootlin’s Allwinner VPU Kickstarter campaign is open through Mar. 18. Basic pledges range from 4 to 64 Euros, and a 128 Euros ($156) pledge gets you a T-shirt. Pledges over 1,000 Euros also let you share a drink with a Bootlin developer. The funded project aims to deliver its VPU code for the Linux kernel in June. More information may be found on the Allwinner VPU support in the official Linux kernel Kickstarter page, as well as at Bootlin.com.
 

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