Various disorganized links to online information regarding the Pine64 board and the SOC on it.
AllWinner’s official github account https://github.com/allwinner-zh Nothing directly relevant to A64 as of today
Pine64 wiki http://wiki.pine64.org/index.php/Main_Page and manufacturer site https://www.pine64.org
Pine64 connector pinout is available here as well http://files.pine64.org/doc/Pine%20A64%20Schematic/Pine%20A64%20Pin%20Assignment%20160119.pdf
For a low level view of other AllWinner SOCS, one of the people at AllWinner has a module for GPIO titled sun4i_gpio info is here https://olimex.wordpress.com/2012/10/23/a13-olinuxino-playing-with-gpios/ It does not yet support the A64 and may never.
The real superhero in the Pine64 Linux world is longsleep https://github.com/longsleep