Notes on ath79 RouterBoard 493G image

[W. Michael Petullo]

I have some feedback about the ATH79 RouterBoard 493G image built from
master, as documented at:

	https://github.com/openwrt/openwrt/pull/3026

First, I was unable to update to the sysupgrade image at:

	https://downloads.openwrt.org/snapshots/targets/ath79/mikrotik/openwrt-ath79-mikrotik-mikrotik_routerboard-493g-squashfs-sysupgrade.bin

while running 19.07.2, although the initial comments on the
pull request above indicate this is possible. I fixed this by
untarring the sysupgrade image, renaming its top-level directory from
sysupgrade-mikrotik_routerboard-rb493g/ to sysupgrade-routerboard/,
and retarring the sysupgrade image.

I suspect something changed between the time of the intial pull request
comment and the eventual merge. Is there a better way of doing
this? DHCP/TFTP booting the ATH79 image directly fails; I suspect this
is due to the size of the image (see the related comments throught the
merge request referenced above).

Second, the boot process fails as follows after performing the sysupgrade:

[    2.117395] UBI: auto-attach mtd2
[    2.120802] ubi0: attaching mtd2
[    3.260133] ubi0: scanning is finished
[    3.326963] ubi0 error: ubi_read_volume_table: not enough PEBs, required 970, available 958
[    3.335627] ubi0 error: ubi_attach_mtd_dev: failed to attach mtd2, error -28
[    3.342742] UBI error: cannot attach mtd2
[    3.347369] /dev/root: Can't open blockdev
[    3.351531] VFS: Cannot open root device "(null)" or unknown-block(0,0): error -6
[    3.358996] Please append a correct "root=" boot option; here are the available partitions:
[    3.367344] 1f00             256 mtdblock0
[    3.367347]  (driver?)
[    3.373884] 1f01            8192 mtdblock1
[    3.373886]  (driver?)
[    3.380420] 1f02          122624 mtdblock2
[    3.380422]  (driver?)
[    3.386951] 1f03              64 mtdblock3
[    3.386953]  (driver?)
[    3.393486] 1f04              44 mtdblock4
[    3.393488]  (driver?)
[    3.400024] 1f05               4 mtdblock5
[    3.400026]  (driver?)
[    3.406554] 1f06               4 mtdblock6
[    3.406557]  (driver?)
[    3.413089] 1f07               8 mtdblock7
[    3.413091]  (driver?)
[    3.419620] 1f08               4 mtdblock8
[    3.419623]  (driver?)
[    3.426155] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
[    3.434403] Rebooting in 1 seconds..

I am not sure what causes this.

-- 
Mike

:wq