OpenEmbedded BSP layer for Rockchip boards

About:

The purpose of this layer is to provide OpenEmbedded BSP support for
Rockchip-based devices using upstream sources as much as possible.

Dependencies:

URI: git://git.openembedded.org/openembedded-core
layers: meta
branch: matched branches (e.g. master, sumo, ...)

URI: git://git.yoctoproject.org/meta-arm
layers: meta-arm, meta-arm-toolchain
branch: matched branches (e.g. master, sumo, ...)

Status of supported boards:

builds and boots wic image:
	32-bit:
		firefly-rk3288
		tinker-board
		tinker-board-s
		vyasa-rk3288

	64-bit:
		nanopi-m4
		nanopi-m4-2gb
		nanopi-m4b
		nanopi-r2s
		nanopi-r4s
		orangepi-5-plus
		radxa-zero-3e
		radxa-zero-3w
		roc-rk3308-cc
		roc-rk3328-cc
		rock-3a
		rock-4c-plus
		rock-5a
		rock-5b
		rock-pi-4a
		rock-pi-4b
		rock-pi-4c
		rock-pi-e
		rock-pi-s
		rock64

builds:
	32-bit:
		marsboard-rk3066
		radxarock
		rock2-square

Notes:

rk3308 rkbin: The latest ddr initializer for the rk3308 platform does not output diagnostic messages to uart0. This causes a bunch of gibberish to be printed to the console window which only becomes legible once the linux kernel starts. I.e. the console output of the ddr initialization routine, as well as u-boot is lost. An older version of this same binary blob does, however, support output to uart0 (making its diagnostic messages as well as u-boot available on the console). By default the build assumes the user would like to see these message and be able to have the option to interact with u-boot.

IOW: for rk3308-based devices, an older version of rkbin is used.

If, however, the user would prefer to use the latest binary ddr
initializer from rkbin, simply set:

	RKBIN_RK3308_LATEST = "1"

in the configuration (e.g. conf/local.conf).

wic compression: For boards which build and boot wic images, the user can optionally specify a compression using the WIC_COMPRESSION_EXTENSION variable. By default "wic" images are built, but if the user would prefer, say "wic.xz" images, simply specify:

	WIC_COMPRESSION_EXTENSION = ".xz"

in the configuration (e.g. conf/local.conf).

A/B updates with RAUC This layer now contains one example of building an A/B update using RAUC. Users are free to use/test this example, to optionally enable it, to build their own update strategies based on this one, or to ignore it completely. This example only works with

	INIT_MANAGER = "systemd"

If you wish to use this example in your builds:
- enable 'systemd' as your init system
- add the meta-rauc layer to your build (with the corresponding branch)
- add 'rauc' to your DISTRO_FEATURES
- enable RK_RAUC_DEMO in your config

If you wish to implement your own RAUC update without using the example from
this layer, perform the same steps as above except for the step enabling
RK_RAUC_DEMO.

HW video decoding with gstreamer

Most Rockchip SoCs have some integrated VPU, either Hantro, RKVDEC or
RKVDECv2. Those are called stateless VPUs and they require tools to be
adapted so they can be used. Upstream ffmpeg doesn't support them (yet)
but gstreamer does, via the v4l2sl* plugins. However, by default those
aren't built in OE-Core. This layer enables these plugins by default for
all SoCs that have at least one VPU (at the time of writing, all SoCs
supported by this layer to the exception of RK3308).

If you wish to NOT build those plugins anymore, you can set

	ENABLE_STATELESS_VPU_GST = "0"

in any appropriate conf file (or in a
gstreamer1.0-plugins-bad_%.bbappend in your own layer).

Note that this is only relevant for upstream-based Linux kernels as
Rockchip have developed their own ABI for their own kernel that isn't
compatible (see Rockchip Media Process Platform (MPP) and
downstream gstreamer-rockchip plugin for those kernels).

U-Boot Environment:

In order to configure U-Boot to be able to store its environment into the
device from which it was booted, for any device supported in this BSP,
simply add the following to MACHINE_FEATURES:

	rk-u-boot-env

If enabled, to additionally have the U-Boot environment generated and
stored in the image, also enable the following variable (default: off):

	RK_IMAGE_INCLUDES_UBOOT_ENV

The script:

	scripts/dump-uboot-env-from-yocto-image.sh

can be used on a rockchip wic image to see the contents of the U-Boot
environment partition at build time.

Maintenance:

Please send pull requests, patches, comments, or questions to the
yocto-patches mailing list (yocto-patches@lists.yoctoproject.org)
CCing the maintainer

When sending patches, please make sure the email subject line includes
"[meta-rockchip][PATCH]" and follow the community's patch submission
guidelines, as described in:
	https://www.openembedded.org/wiki/Commit_Patch_Message_Guidelines
	https://www.openembedded.org/wiki/How_to_submit_a_patch_to_OpenEmbedded

This can be configured within the repository with the following commands:

	git config sendemail.to yocto-patches@lists.yoctoproject.org
	git config sendemail.cc <your full email address>
	git config format.subjectprefix "meta-rockchip] [PATCH"

Then, to send your most recent commit (i.e. just one patch),
please use something like:

	git format-patch -M -1
	git send-email <your patch file>

Maintainer:

Trevor Woerner <twoerner@gmail.com>

Brief History:

2014 April
	- originally started by Julien Chauveau
	- Romain Perier joins
2014 Sep
	- Julien leaves
2015 Aug
	- Trevor Woerner joins
2017 Mar
	- developers from Rockchip fork this layer see:
		https://github.com/rockchip-linux/meta-rockchip.git
		http://rockchip.wikidot.com/yocto-user-guide
2017 May
	- Romain leaves
2018 Feb
	- Rockchip developers abandon their fork for buildroot
		http://opensource.rock-chips.com/wiki_Buildroot