Debian Works Towards ARMv8 AArch64 Support

Debian developers are working towards an official armhf image for the Wheezy release and they're also gearing up for official 64-bit ARMv8 / AArch64 support in the "Wheezy + 1" release.

On Tuesday of this year's DebConf in Nicaragua there were two sessions concerning the ARM architecture support within the Debian world. Both sessions were led by Steve McIntyre, the former Debian Project Leader and is currently employed by ARM Holdings out of Cambridge.

The first talk concerning Debian ARM just went over the different ports: the Debian "armel" version that was introduced in Debian Lenny with a soft-float EABI and v4t target and the armhf version that will be first introduced with Debian Wheezy as an ARMv7 target with hard floating-point support. ARMv7 with hardware floating-point support is the new standard for Linux ARM distributions and has already been the default in Ubuntu Linux for months. As earlier Phoronix benchmarks have shown, ARM hardfp support can cause noticeable performance gains for many different workloads.

There's also an unofficial Debian port going on that targets ARMv6 due to the Raspberry Pi. Sadly, the low-cost Raspberry Pi ARM SoC from Broadcom is ARMv6 rather than ARMv7 so it isn't supported by the new Debian hardfp variant. This ARMv6 "Raspbian" version targeting the Raspberry Pi will not become an official Debian port.

The Debian ARM developers are also looking at ARM virtualization support, LPAE support for 32-bit with support for large physical address extension (similar to PAE on Intel hardware for the 32-bit kernel support more than 4GB of system RAM), UEFI as the standard boot architecture, DeviceTree, and ACPI support.

When Steve McIntyre was asked why the ARM SoC vendors are so anti-open-source friendly when it comes to the graphics support, he said there is no good reasion why most of the players will not share besides wanting to protect their "special sauce" from the competition. "You're going to essentially need binary blobs forever," said Steve. He also went on to say that the vendors are likely more scared of patent trolls than they are of releasing this "secret sauce" to their competing ARM SoC vendors. "Lawyers... I wish we didn't need them."

Immediately following this basic ARM talk was a second talk specifically focusing upon AArch64, the ARMv8 64-bit architecture. It was only last week that ARM Holdings began to publish the 64-bit AArch64 ARMv8 Linux kernel patches. Said during this talk was basically that Debian will hopefully have an official ARMv8 version for the release that succeeds Debian 7.0 Wheezy, which might be called Debian Zurg or Shark.

ARMv8 hardware will continue to support ARMv7 32-bit software, will have VFPv3 from ARMv7 and ARM Neon SIMD, and will continue to support SecureZone as the security extensions. This new architecture will also support LPAE and virtualization plus the other features that have been talked about recently. This hardware won't actually appear until 2013 with more of the ARMv8 specifications not even coming until the end of this calendar year.

ARM Holdings has developed a "FastModel" implementation of ARMv8 that uses Ubuntu and the Linux 3.4 kernel, which Steve showed off during his talk, except ARM isn't publicly releasing this emulated version yet. He also says right now ARM hasn't yet released enough information to develop ARMv8 architecture QEMU support, but that the needed information should be released soon.

The ARMv8 tool-chain is already working under Linux too, except there's some patches that ARM has yet to release. "ARM legal won't let any of the patches be sent in yet." Linaro is also busy working on ARMv8 Linux support. The internal ARM team has been porting Ubuntu Natty to ARMv8, which will be able to benefit the Debian Linux project, assuming this code gets released. Steve also said ARM should be releasing other ARMv8 details soon.