[LEDE-DEV] [openwrt/openwrt] ar71xx: Ubiquiti Airmax M: add relocate-kernel to invalidate cache
mschiffer at universe-factory.net
Thu Apr 26 13:10:59 PDT 2018
On 04/26/2018 09:22 PM, Etienne Champetier wrote:
> Hi Matthias,
> 2018-04-26 11:43 GMT-07:00 LEDE Commits <lede-commits at lists.infradead.org>:
>> neoraider pushed a commit to openwrt/openwrt.git, branch lede-17.01:
>> commit eed9d40133fe6468cc253d0345c7d7332d2aaa7c
>> Author: Matthias Schiffer <mschiffer at universe-factory.net>
>> AuthorDate: Thu Apr 26 20:04:48 2018 +0200
>> ar71xx: Ubiquiti Airmax M: add relocate-kernel to invalidate cache
>> Some Ubiquiti U-boot versions, in particular the "U-Boot 126.96.36.199-s956
>> (Jun 10 2015 - 10:54:50)" found with AirOS 5.6, do not correctly flush the
>> caches for the whole kernel address range after decompressing the kernel
>> image, leading to hard to debug boot failures, depending on kernel version
>> and configuration.
>> As a workaround, prepend the relocate-kernels loader, which will invalidate
>> the caches after moving the kernel to the correct load address.
> So if I understand correctly,
> with this commit I don't need to downgrade my bullet M to v.5.5.10
> (U-Boot 188.8.131.52-s594 (Dec 5 2012 - 15:23:07))
> and I can just downgrade to v.5.6.x (U-Boot 184.108.40.206-s956 (Jun 10 2015
> - 10:54:50)) and maybe even the firsts 6.0.X (without the signed
> mtdparts differences between the 2 uboot version:
AFAIK, both AirOS 5.5 and 5.6 use the same flash layout. The mtdparts with
the EEPROM at 0x00730000 (also described in
https://wiki.openwrt.org/toh/ubiquiti/airmaxm ) is bogus and was not
directly caused by the newer Uboot or AirOS, but by installing "broken"
OpenWrt images (everything before ) from AirOS 5.6; the commit message
of  contains further details. Certain Uboot versions coming with 5.6
also did not unlock the flash chip, leading to unwritable flash on OpenWrt
(fixed in ).
The cache invalidation issue recently appeared after the update to kernel
4.4.120 in lede-17.01, but I'm not sure if the OpenWrt/LEDE default kernel
configuration is affected.
With these 3 fixes, installing OpenWrt from AirOS 5.6 should work fine; I
don't know about 6.0. It seems that I never backported  to lede-17.01
because it requires 2 other patches on kernel 4.4, but we have a downstream
patch for that in Gluon .
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