Notes on edison support (currently not working)

Thu May 7 01:04:44 UTC 2015

Hi,

I've tried enabling the Edison; haven't succeeded so far, but thought I'd
share my latest status in case someone wants to help or pick it up. (Help
welcome!)

== Overview of Edison boot ==

0) plug micro USB and connect with screen to see boot sequence

1) boot ROM loads firmware from eMMC; if firmware isn't found, an USB load
is attempted

******************************
PSH KERNEL VERSION: b0182727
                WR: 20104000
******************************

SCU IPC: 0x800000d0  0xfffce92c

PSH miaHOB version: TNG.B0.VVBD.0000000c

microkernel built 23:15:13 Apr 24 2014

******* PSH loader *******
PCM page cache size = 192 KB
Cache Constraint = 0 Pages
Arming IPC driver ..
Adding page store pool ..
PagestoreAddr(IMR Start Address) = 0x04899000
pageStoreSize(IMR Size)          = 0x00080000

*** Ready to receive application ***

2) firmware loads u-boot

U-Boot 2014.04 (Aug 20 2014 - 16:08:32)

       Watchdog enabled
DRAM:  980.6 MiB
MMC:   tangier_sdhci: 0
In:    serial
Out:   serial
Err:   serial
Hit any key to stop autoboot:  0

3) u-boot default config will attempt a flash over USB (via dfu-util) then
fallback to booting from eMMC.

U-Boot also offers some manual commands to trigger an OTA update from a
special partition which you can mount from your host (via USB gadget
driver) when the device boot it's default Yocto/Poky rootfs

4) Yocto loads and offers a console on USB serial

== Target installation to eMMC and intermediate installation to micro SD ==

Ideally, snappy would be running of the eMMC but the partitions / available
space are too small.

However, the eMMC partitions are defined when flashing the initial Edison
image. To change this, it's possible to rebuild Yocto/Poky from sources;
this takes about 30G of space and half a day. The output are the files
you'd write to the eMMC over USB to reflash. This describes the process:
http://fr.slideshare.net/FantomJAC/how-to-hack-edison

So a nicer intermediate step, especially during development, would be to
boot from external micro SD. Unfortunately, U-Boot doesn't support the
external SD, only the eMMC.

My next bet was to extract target kernels and initrd from a snappy micro
SD, copy these to eMMC by hand, then use u-boot to launch snappy from micro
SD. Because U-Boot only supports FAT and not ext4, I've looked for a
sufficiently large partition to hold my kernel and initrd (the one where
the Yocto vmlinuz resided was too small even for my own kernel).

I settled on the update partition which is a disk image (with a FAT
partition in that disk image) as to be exposed via the gadget driver to
USB. I had to format it to be a plain partition rather than a disk image
with a partition table and a partition. To do this, run the following from
a booted Yocto:
mkfs.vfat -F32 -I /dev/mmcblk0p9
(then mount /dev/mmcblk0p9 as you please; the micro SD is at /dev/mmcblk1p*)

This could work, but currently fails to boot (see below).

== Current state of snappy bits ==

First, I generated an i386 snappy image starting from the generic-amd64 OEM
snap and creating my own local generic-i386 snap; it's at:
http://people.canonical.com/~lool/generic-i386_1.1.1_all.snap
I guess we should have an official i386 OEM snap, or I should upload an
unofficial one.

Then I created a 15.04 image with:
sudo ubuntu-device-flash core 15.04 --channel edge --oem
generic-i386_1.1.1_all.snap --developer-mode --output x86.img
and wrote it to micro SD.

I mounted this micro SD from Edison's Yocto install, copied the bits to the
newly formatted update partition and tried booting this, but I get no
output:
================
boot > setenv bootargs earlyprintk=ttyMFD2
 root=/dev/disk/by-label/system-a console=ttyMFD2 init=/lib/systemd/systemd
ro
boot > fatload mmc 0:9 0x100000 vmlinuz
reading vmlinuz
6239536 bytes read in 154 ms (38.6 MiB/s)
boot > zboot 0x100000
Valid Boot Flag
Setup Size = 0x00004400
Magic signature found
Using boot protocol version 2.0d
Linux kernel version 3.19.0-16-generic (buildd at phianna) #16-Ubuntu SMP Thu
Apr 30 16:13:00 UTC 2015
Building boot_params at 0x00090000
Loading bzImage at address 00100000 (6222128 bytes)
Magic signature found
Kernel command line: "earlyprintk=ttyMFD2 root=/dev/disk/by-label/system-a
console=ttyMFD2 init=/lib/systemd/systemd ro"

Starting kernel ...
================

so I reverted to Edison Yocto kernel + our initrd (our initrd is required
to setup the proper mounts).

I had to recompress our initrd with gzip instead of xz as xz compression is
not enabled in the Edison kernel. This does produce output, but fails
without a clean error message; also note I had to pass ramdisk_size in
bootargs and compute sizes by hand:
fatload mmc 0:7  0x100000 vmlinuz
fatload mmc 0:9 0x8100000 initrd-gz
zboot 0x100000 5124192 0x8100000 19333091
=================
Using boot protocol version 2.0c
Linux kernel version 3.10.17-poky-edison+ (sys_dswci at ncsndgbuild04) #1 SMP
PREEM
PT Wed Aug 20 16:09:18 CEST 2014
Building boot_params at 0x00090000
Loading bzImage at address 00100000 (5108832 bytes)
Magic signature found
Initial RAM disk at linear address 0x08100000, size 422785169 bytes
Kernel command line: "earlyprintk=ttyMFD2 root=/dev/disk/by-label/system-a
console=ttyMFD2 init=/lib/systemd/systemd ro ramdisk_size=50000"

Starting kernel ...

[    0.000000] Initializing cgroup subsys cpuset
[    0.000000] Initializing cgroup subsys cpu
[    0.000000] Initializing cgroup subsys cpuacct
[    0.000000] Linux version 3.10.17-poky-edison+ (sys_dswci at ncsndgbuild04)
(gcc version 4.8.2 (GCC) ) #1 SMP PREEMPT Wed Aug 20 16:09:18 CEST 2014
[    0.000000] e820: BIOS-provided physical RAM map:
[...]
[    0.000000] Kernel command line: earlyprintk=ttyMFD2
root=/dev/disk/by-label/
system-a console=ttyMFD2 init=/lib/systemd/systemd ro ramdisk_size=19333091
[...]
[    0.505057] Trying to unpack rootfs image as initramfs...
[    2.671179] rootfs image is not initramfs (junk in compressed archive);
looks
 like an initrd
[    3.627260] Freeing initrd memory: 412880k freed
[...]
[    7.271674] RAMDISK: gzip image found at block 0
[    7.619697] mmc2: queuing unknown CIS tuple 0x91 (3 bytes)
[    7.625144] mmc2: new ultra high speed DDR50 SDIO card at address 0001
[    9.966756] List of all partitions:
[    9.970252] b300         3817472 mmcblk0  driver: mmcblk
[    9.970350]   b301            2048 mmcblk0p1
d117f98e-6f2c-d04b-a5b2-331a19f91cb2
[    9.970444]   b302            1024 mmcblk0p2
25718777-d0ad-7443-9e60-02cb591c9737
[    9.970535]   b303            2048 mmcblk0p3
8a4bb8b4-e304-ae48-8536-aff5c9c495b1
[    9.970624]   b304            1024 mmcblk0p4
08992135-13c6-084b-9322-3391ff571e19
[    9.970714]   b305            1024 mmcblk0p5 333a128
=================
I suspect my initramfs is not unpacked properly; not sure how to fix that.

Help is welcome on the kernel output and on the initramfs issue!  :-)

== Recovering from a broken bootloader ==

To reflash a broken u-boot, you will need to reflash the firmware then
reflash u-boot + system; this should a simple matter of running
flash-all.sh from the Intel downloads, but you need a special tool to send
the firmware over USB:
http://sourceforge.net/projects/xfstk/files/

Cheers,
-- 
Loïc
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