Just got my (first) PINE64 or PINE A64

https://www.pine64.com
http://wiki.pine64.org
http://linux-sunxi.org/A64
http://linux-sunxi.org/Pine64

It sports an Allwinner A64.  Like Broadcom Allwinner is typically
protective of their documentation.  But lately with the C.H.I.P and
now this (and sure others) the docs are not hard to find and
Allwinner doesnt seem to be taking them down.

I have hesitated with both brands, and passed up on a great many
allwinner based boards initially for lack of documentation.  But the
C.H.I.P kind of won me over to try some more.  It is brickable but
you have to work a little at it, there is a FEL jumper for that board
that you can essentially use usb to get into the chip and re-load.

This one so far appears to be sd card based like the raspberry pi.
Unlike it though the ARM boots the system not some other processor.

Naturally if you see my other stuff I have no interest in running
Linux, I am interested in bare metal.  As with the raspberry pi
I would love to write the first software that runs and bring up
everything.  I dont know that the documentation is there, and I know
when you have a full staff, software engineers, hardware (chip and pcb)
it takes like 10 months to bring up ddr.  Granted in theory there is
code already, actualy a BSP appears to be available.  So I am going to
just run from the bootloader like one would if they were porting an
operating system.

I wasnt interested in one of the full blown operating system sd card
images that take hours to download.  I found through the wiki I think
this one

https://www.stdin.xyz/downloads/people/longsleep/pine64-images/

I grabbed simpleimage-pin64-latest.img.xz

Then from their README.txt

xzcat simpleimage-pine64-20160207-1.xz | pv |sudo dd of=/dev/sdX bs=1M oflag=sync

where /dev/sdX is your sd card, yes, get this wrong and you could blow
away a hard drive.

http://linux-sunxi.org/Pine64

says

UART0 is the main UART used by Allwinner's firmware for boot and debug
messages and is accessible on pins 29 (TXD), 30 (RXD), 25/34 (GND) on
the Euler connector (this is not mentioned in the official connector
description).

And this is true so far.  Using an ftdi breakout (3.3v) of some sort
or ftdi cable, same thing you would use for a raspberry pi or C.H.I.P
you can see this boot, with the sd card there.

All that whole page is interesting.  The uart section, the Boot sequence
you need a special A to A usb cable (not really that special but not
something everyone has) to run sunxi-fel.

Otherwise it comes up in 32 bit mode and with the sd card tries to boot
that.

So we are hooked up to uart0, prepare our sd card plug it in.  Note
mine was shipped with a button floating around in the bag, I thought
it was an insect at first.  Then there was a note that said this is not
a broken part, they basically provided one button that fits into both
the power and reset, you get to choose and do your own soldering.  I
get that not everyone has the tools for that.  Easy to do for the
most part, but not something everyone has.  I naturally put mine on
the reset.  Likewise I see they have two pads for user leds but didnt
populate those either...

We hit any key to stop autoboot and get the sunxi prompt.

Unlike some uboots, this does not have an xmodem download feature.
But that is okay, can get around that in a few ways.  Before doing
that though

http://linux-sunxi.org/A64

Has the datasheets we need.  And no surprise uart0 is at or roughly
at the same place as other allwinner chips

#define UART_BASE 0x01C28000

So from that prompt if we were to write a byte to the transmit register
(offset 0) it should show.


Hit any key to stop autoboot:  0
sunxi#mw.b 0x01c28000 0x55
Usunxi#mw.b 0x01c28000 0x56
Vsunxi#

So we are not well on our way to doing something.

the printenv command shows us this

kernel_filename=pine64/Image
load_addr=41000000

So lets start with 0x41000000 as the base address in ram where we do
stuff.

No LEDs installed so an LED blinker is not the first example.
uart01 is.

I generate an additional output which is a dump of the binary in a
way that we can literally cut and paste it into the terminal with uboot.

mw.l 0x41000000 0xEAFFFFFF
mw.l 0x41000004 0xE3A0D442
mw.l 0x41000008 0xE28DDA01
mw.l 0x4100000C 0xEB00003B
mw.l 0x41000010 0xEAFFFFFE
mw.l 0x41000014 0xE5801000
mw.l 0x41000018 0xE12FFF1E
mw.l 0x4100001C 0xE5900000
...

If you cut and paste the whole thing in, then use the go command
to run from 0x41000000, uart01 echoes back what you type.

sunxi#mw.l 0x41000134 0xEAFFFFF6
sunxi#mw.l 0x41000138 0x12345678
sunxi#go 0x41000000
## Starting application at 0x41000000 ...
12345678
asdf

Major progress.  Really want a bootloader with a way to download
programs (over the uart).  I have historically used proprietary
things, xmodem, intel hex, and now am switching to motorola srecord.

https://en.wikipedia.org/wiki/SREC_(file_format)

I like the S3 format with a full 32 bit address...

So bootloader01 is that bootloader.

It leaves a little room for programs to be downloaded.

.globl _start
_start:
    b   reset

.space 0x20000-4,0

reset:
    mov sp,#0x42000000
    bl notmain
hang: b hang

can of course make that larger if you want.

You can take the mw.l approach and then probably use tools to write
that to the sd card which is our storage.  Or better than that just
pull the sd card, copy notmain.bin in the bootloader01 directory to
lets say /mount/whatever/BOOT/bootloader.img

wherever you have it mounted, mine shows up with three mounts the
BOOT one is the one you want.

Power on or reset with that card, hit any key to stop autoboot.

Now this part could have been done against files on the filesystem
too, but I have not messed with that yet.

sunxi#setenv bootcmd 'fatload mmc 0:1 41000000 bootloader.img; go 0x41000000'
sunxi#saveenv

Now when you reset/reboot, it boots into this bootloader if you dont
press a key to stop autoboot.

reading bootloader.img
131964 bytes read in 17 ms (7.4 MiB/s)
## Starting application at 0x41000000 ...
12345678

SREC

And now we can for example take the uart01 example and download in
ascii or raw mode or whatever your dumb terminal calls it (or cut
and paste) using the notmain.srec file.  With minicom ctrl-a then
s then down (or up) to ascii, then the path to the file.  Once
downloaded then press g for go and it will start the program you
downloaded.  If uart01 then you can type stuff and it echos back out.

SREC
41000000
12345678
asdfasdf

So now we have an easy way to load and run programs.  And you can see
why soldering the loose button to reset was a good idea.