AnsweredAssumed Answered

Invalidatin Cortex-A9 SCU

Question asked by Vincent Siles on Sep 12, 2016
Latest reply on Oct 10, 2016 by Yuri Muhin

Hi !

I'm trying to understand how to enable ACTLR.SMP and the SCU on our own secure OS, and the Cortex-A9 TRM states that:

For the primary processor:
1. Invalidate:
   • the SCU duplicate tags for all processors
   • the data cache.
2. Enable the SCU.
3. Enable the data cache, set the SMP mode with ACTLR.SMP=1.

While reading Linux code, I found that the SCU is enabled quite late in the boot process (mmu is already on, and L1/L2 caches are already configured), and the only bit set at this time are ENABLE and STANDBY_ENABLE. I can't find any invalidation of the SCU tags.


  1. Is not invalidating the SCU before enabling an issue ?
  2. Why does Linux enables the SCU so late in the boot process ?