#define isb() __asm__ __volatile__ ("" : : : "memory") is in arch/arm/include/asm/system.h. In my build, that is going into set_cr(), producing no instruction.

Is that correct? It has been in code since http://lists.denx.de/pipermail/u-boot/2009-March/049870.html.

Looks like it's used only in set_cr. Other points in the code have nonempty code for ISB, for example #define CP15ISB asm volatile ("mcr p15, 0, %0, c7, c5, 4" : : "r" (0)) which is in armv7.h

I don't have a standard reference platform to experiment with. The platform that I have uses a Cortex-A9 core, u-boot.2012.07 is ported and running. There are some intermittent issues there relating to enabling MMU/cache, lack of instruction barriers would be a plausible explanation.

Adding ISB SY in set_cr doesn't fix my issues, but it looks like a step in right direction. If someone could explain, or point me to email, I would appreciate it. Thanks in advance.