[LEDE-DEV] [RFC] brcm47xx: bump kernel to 4.4

[Hannu Nyman]

On 25.10.2016 9:13, p.wassi at gmx.at wrote:
>> It seems I'm experiencing the same crazy problem. Local builds work
>> for me (as explained in commit message), but image from buildbot
>> doesn't boot. This is some totally crazy thing :|
> I opt for staying at 4.4 and not reverting, since the issue already occured
> on kernel 4.1 for the WRT54GL (and probably other devices as well?).
> So it's _not_ a 4.1 -> 4.4 issue! The last kernel, that booted fine
> on my devices (with buildbot images) was OpenWRT 15.05.1 - 3.18.23
> As you've experienced yourself: local images also work fine. With 4.1 and 4.4.

This freezing after "> Starting program at 0x80001000" reminds me of an old 
issue on ar71xx/WNDR3700:

This might be something related to uncompressing the image by the bootloader. 
Kernel & firmware size growth may be exposing some compression/uncompression 
problem that gets semi-arbitrarily triggered now (when the images sizes have 
grown due to kernel size growth?). It is possible that the old bootloader 
fails to decompress the image but has no proper verbose error message about that.

There was something rather similar four years ago with ar71xx-based 
WNDR3700/WNDR3800 series. There the problem was fixed by decreasing the 
compression dictionary size used for WNDR3700/3800 devices. I debugged that 
after receiving a hint from Rafal (who had had a bit similar problems with 
WNDR4500). Rafal's last message of a long thread:
https://lists.openwrt.org/pipermail/openwrt-devel/2012-June/015846.html

For reference, the ar71xx WNDR3700 debugging:
https://forum.openwrt.org/viewtopic.php?id=40565
https://lists.openwrt.org/pipermail/openwrt-devel/2012-November/thread.html#17445
https://dev.openwrt.org/ticket/12454#comment:12