[meta-freescale] imx6 silent memory corruption

[Nikolay Dimitrov]

Hi guys,

Just to share my progress so far. My board passed 500+ iterations of
DDR stress testing with the FSL tool (this bloody thing took 2 days to
complete!). Tried the U-Boot integrated memory tests (both quick and
alt), and they didn't show any issues. So I can say that at least the
hardware and DDR settings seems to be OK.

In addition, I tried to disable SMP, L2 & L1 cache support in my kernel
and see what happens, but I can still observe the corruption. I found
that there's an embedded memory tester in the kernel, but only for x86
(CONFIG_MEMTEST), not useful for ARM.

I started to doubt that my 2 cross-build machines (x64 Debian stable)
are maybe producing broken kernels, so did a test cross-build on Ubuntu
14.04, and even did native build on riotboard, but the results are the
same - issue can be still observed.

During boot and operation I sometimes see kernel oopses (I remember
most of them related with execve and filesystem reads), sometimes apps
segfault. Kernel and/or toolchain issues are also possible but I
checked that Daisy has the gcc-4.8+ PR58854 patch, so not very likely,
especially if other Yocto users don't report such issues.

Possible step forward is to try to build original FSL 3.10.17 version
without my local patches, and maybe even build a minimal 3.18+ mainline
kernel to see how it behaves in the same test case. Someone can even
joke that it's time to leave the dusty old Daisy and go forward with
Dizzy and 3.10.53.

Regards,
Nikolay