A20

dwlinux_gs 2014-09-27

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A20
Allwinner_A20.jpg
Manufacturer	Allwinner
CPU	Dual-Core ARM Cortex-A7
Memory	LPDDR3/DDR3/LPDDR2
GPU	Mali400 MP2
Connectivity
Video	HDMI 1.4, CVBS, YPbPr, VGA, CPU/RGB/LVDS LCD
Audio	I2S, PCM, AC97
Storage	MMC, NAND
USB	OTG, 2x Host
Release Date	December 2012
Website	Product Page

Allwinner A20 (sun7i) SoC features a Dual-Core Cortex-A7 ARM CPU, and a Mali400 MP2 GPU from ARM.

Allwinner A20 is a low-end (budget) version of the A31. It shares its Cortex-A7 ARM CPU architecture, but at the same time it is also pin-to-pin compatible with A10.

A20 is fully supported by the community from linux-sunxi 3.4 kernel and later.

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Overview

A20 CPU consists of dual ARM Cortex-A7 cores, and integrates the Mali400 MP2 GPU. Together with CedarX multimedia processing unit that is capable of up to 2160p (3840x1080@30fps 4k resolution or 1080p 3D decoding) video decoding, with integrated HDMI 1.4 output support, and H.264 HP (High Profile) in 1080p at 30fps video encoding.

Main components of the A20

CPU: Dual-Core ARM Cortex-A7 1GHz Processor which have both VFP4 and NEON SIMD co-processors that share 32 floating point double-precision registers together^[1]:
- FPU: standard ARM VFPv4-D32 FPU Floating Point Unit
- SIMD: NEON (ARM's extended general-purpose SIMD vector processing extension engine)
GPU: Mali400 MP2
VPU: CedarX (Video Processor Unit for audio and video hardware decoding or encoding)
HDMI-transmitter: HDMI CEC (Consumer Electronics Control)

Cortex-A7

Cortex-A7 is 100% ISA compatible with the Cortex-A15, this includes the new virtualization instructions, integer divide support and 40-bit memory addressing. Any code running on an A15 can run on a Cortex A7, just slower. This is a very important feature as it enables SoC vendors to build chips with both Cortex A7 and Cortex A15 cores, switching between them depending on workload requirements. ARM calls this a big.LITTLE configuration.^[2]^[3]^[4]

Virtualization

Cortex A7 and A15 includes hardware virtualization support.

It is managed by Xen (Presentation of Cortex A7 and A15 capabilities for virtualisation, Xen ARM on , PVH mode on blog., Xen ARMv7 with Virtualization Extensions on wiki)

there is a guide about running xen on a20

Some guides to deploy virtualization on Cotex-A15 and source for virtualization with KVM on Cortex-A15 on github

Open Kernel Labs Delivers OKL4 Mobile Virtualization for ARM Cortex-A7 Processors

On the kvm branch of , there is description of Cortex-A15 Virtualization extensions VGIC registers :

GIC of ARM on kvm branch of the kernel

After the ARM Cortex-A7 documentation:

GIC memory MAP on Cortex-A7^[5]:

0x4000-0x4FFF      Virtual interface control, common base address
0x5000-0x5FFF   Virtual interface control, processor-specific base address
0x6000-0x7FFF   Virtual CPU interface

Virtual Maintenance Interrupt (PPI6)^[6]
2 virtual interrupt signals, nVIRQ and nVFIQ^[7]
With MMU-400, Intermediate Physical Address (IPA) ca be used by guest OS^[8]

A20 SoC Features

A20 SoC on a Cubieboard2

CPU
- ARM Cortex-A7 Dual-Core
- 256KiB L2-Cache (shared between two cores)
- 32KiB (Instruction) / 32KiB (Data) L1-Cache per core
- SIMD NEON, VFP4
- Virtualization
- Large Physical Address Extensions (LPAE) 1TB
GPU
- ARM Mali400 MP2
- Featuring 1 vertex shader (GP) and 2 fragment shaders (PP).
- Complies with OpenGL ES 2.0
Memory
- LPDDR2/DDR3/DDR3L controller
- NAND Flash controller and 64-bit ECC
Video
- HD H.264 2160P video decoding
- Full HD video decoding
- BD Directory, BD ISO and BD m2ts video decoding
- H.264 High Profile 1080P@30fps encoding
- 3840×1080@30fps 3D decoding
- Complies with RTSP, HTTP,HLS,RTMP,MMS streaming media protocol
Display
- Support multi-channel HD display
- Integrated HDMI 1.4
- CPU/RGB/LVDS LCD interface 1920×1080 resolution
- CVBS/YPbPr/VGA support
- Integrated TV decoder
Camera
- Integrated parallel 8-bit I/F YUV sensor
- Integrated 24-bit parallel YUV 444 I/F
- 5M/8M CMOS sensor support
- Dual-sensor support
Audio
- Integrated HI-FI 100dB Audio Codec
- Dual MIC noise cancellation

Documentation

Software

Original SDKs

We have made some SDKs available on our server:

A20-SDK-2.0 (Full
A20_SDK_20130319 (Reduced, Unpacked)

GPL Violations

The publically available SDKs contain kernel and u-boot trees which include and depend on several binaries. Allwinner is violating the GPL quite directly here.