Parallella

Resources

Home

Wikipedia

The Adapteva Parallella is a family of credit card sized single board computers. Based on the dual-core Zynq-7000 series of ARMv7-A processors, they also contain a built-in FPGA and Epiphany-III 16-core co-processor. The board is intended to democratise access to parallel programming, due to the price, number of cores and low power draw (5W).

The Parallella was crowdfunded via Kickstarter, and the schematics and design files were released as open source.

Hardware

Generally available Parallella hardware comes in three forms:

• Parallella-16 Micro Server
• Parallella-16 Desktop Computer
• Parallella-16 Embedded Platform

Kickstarter backers would have been able to receive a limited number of Parallella-64s with a 64-core co-processor, but these were not mass-produced and are not covered here.

Parallella-16s can be powered by 2A 5V DC barrel jack (5.5mm OD/2.1mm ID centre-positive), microUSB (with jumper) or by the metal pads in the corners via the J15 header.

Parallella-16 Micro Server

Device	Make/model	Status	Kernel driver(s)	Kernel version	Notes
CPU	Dual-core Zynq-7010	Works	ARCH_ZYNQ
Memory	1GB DDR3L	Works
Co-processor	16-core Epiphany-III	Works	EPIPHANY	parallella-linux
Ethernet	10/100/1000	Works	ARM_AMBA		Max. 1500 MTU
Storage	microSDXC	Works	ARM_AMBA
Serial	UART	Works

Parallella-16 Desktop Computer

Includes all hardware of the Parallella-16 Micro Server, additionally with:

Device	Make/model	Status	Kernel driver(s)	Kernel version	Notes
USB	microUSB OTG	Works
Video	microHDMI	Works
GPIO		24			via Porcupine board

Parallella-16 Embedded Platform

Includes the hardware of the Parallella-16 Desktop Computers, except the CPU is upgraded to the Zynq-7020. EP devices must use FPGA firmware built for Zynq-7020 devices.

Device	Make/model	Status	Kernel driver(s)	Kernel version	Notes
CPU	Dual-core Zynq-7020	48 (Untested)	ARCH_ZYNQ		includes Bank 13 I/O pins

Installation

SD Card

The Parallella finds its firmware, bootloader, kernel and device tree necessary to boot on the SD card. In order for the board to find these files, the SD Card must be MBR/DOS partitioned, with the first partition FAT32 formatted.

root #lsblk

NAME             FSTYPE   LABEL MOUNTPOINT
/dev/mmcblk0
├─/dev/mmcblk0p1 vfat     BOOT  /boot
└─/dev/mmcblk0p2 ext4     ROOT  /

root #tree /boot

/boot
├── devicetree.dtb
├── parallella.bit.bin
└── uImage

Firmware

Parallella boards load the FPGA firmware (including u-boot bootloader), kernel (uImage) and device tree (dtb) from the microSD card slot whenever power is applied to the board.

The firmware file must be named parallella.bit.bin on the FAT32 filesystem on the SD card.

This firmware is open sourced on Github parallella/oh but requires the free (as in beer) Xilinx Vivado tools to produce.

Versions

Parallella has provided 4 versions of the firmware (parallella.bit.bin) that boots Linux:

Date	Elink	Status	Notes	Source
2019.1	elink2	latest	HDMI and headless	Github parallella/parabuntu fpga_bitfiles
2016.11	elink2		HDMI and headless	Github parallella/parabuntu commit 0cb190a
2016.3	elink2		Headless only	Github parallella/parabuntu commit d36f6be
2014.11	elink1		HDMI and headless	Github parallella/parallella-hw old bitstreams

Post-boot customisation

Once the operating system is running, the FPGA can be reconfigured with a compatible bitstream by use of the /dev/xdevcfg driver, or, in more recent kernels, the FPGA Manager.

Kernel

The firmware parallella.bit.bin, in addition to the FPGA routines that concern board bring-in, contains u-boot to boot the system into Linux. The load address for a kernel uImage is 0x8000.

Parallella provide kernel sources with working Epiphany drivers in the parallella-linux repository. parallella-linux provides the parallella_defconfig target to generate a kernel config suitable for all Parallella boards.

user $make parallella_defconfig

user $make uImage LOADADDR=0x8000

Branch	Status	Based on
parallella-linux-2019.1	Works	adi-linux-4.14.0
parallella-linux-2016.11	Works	adi-linux-4.6.0
parallella-linux-2016.3	Works	adi-linux-4.4.0

Upstream kernels can also work, however the Epiphany driver has not been upstreamed. Upstream kernels have the multi_v7_defconfig which is suitable for the Parallella.

user $make multi_v7_defconfig

Building a kernel requires the sys-devel/bc package, and building a uImage requires the dev-embedded/u-boot-tools package:

root #emerge --ask sys-devel/bc

root #emerge --ask dev-embedded/u-boot-tools

The resulting uImage can be found at arch/arm/boot/uImage. The kernel uImage must be named uImage on the FAT32 filesystem on the SD card.

Device Tree

The device tree is available in the parallella-linux sources at arch/arm/boot/dts/zynq-parallella*.dts. It can be compiled into a dtb file with make dtbs:

root #emerge --ask sys-apps/dtc

user $make dtbs

The device tree must be named devicetree.dtb on the FAT32 filesystem on the SD card.

Name	Board
zynq-parallella-microserver.dtb	Parallella MicroServer
zynq-parallella-headless.dtb	Parallella (Desktop or Embedded) without HDMI bitstream
zynq-parallella.dtb	Parallella with HDMI bitstream

Root Filesystem

The upstream device tree (zynq-parallella1.dtsi) configures the root partition as the second partition with an ext4 filesystem.

An armv7a stage3 can be unpacked and customised. Gentoo autobuilds can be found on distfiles.gentoo.org.

Epiphany SDK (esdk)

Adapteva provides the SDK to interact with the Epiphany device on Github adapteva/epiphany-sdk.

Version 2016.3 of the esdk utilises the elink2 interface with the Epiphany chip and requires an elink2 firmware.

The esdk sources build for the armv7l architecture which is not the same as the Gentoo architecture (armv7a).

Cross-compiling

A compatible cross-compiler can be generated with crossdev:

root #crossdev -S -t armv7a-unknown-linux-gnueabihf

When cross-compiling the kernel, call make with the ARCH and CROSS_COMPILE environment variables:

user $make ARCH=arm CROSS_COMPILE=armv7a-unknown-linux-gnueabihf-

When cross-compiling the Epiphany SDK, use the -c armv7a-unknown-linux-gnueabihf flag:

user $git clone https://github.com/adapteva/epiphany-sdk sdk

user $./sdk/build-epiphany-sdk.sh -d -R -c armv7a-unknown-linux-gnueabihf

External Resources

• Parallella hardware design files are available on Github parallella/parallella-hw.
• Xilinx Vivado Design Suite to create the FPGA firmware files