Subject: BUG: Patch "Convert some mftb/mftbu into mfspr" breaks MPC885

From: leroy christophe <[email-masked]>
Date: Wed, 20 Nov 2013 10:37:21 +0100

Scott,

The patch "Convert some mftb/mftbu into mfspr" 
(beb2dc0a7a84be003ce54e98b95d65cc66e6e536 
<https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/arch/powerpc/include/asm/reg.h?id=beb2dc0a7a84be003ce54e98b95d65cc66e6e536>) 
breaks startup on MPC885.

The CPU traps (SoftwareEmulation trap) at sched_clock() when trying to 
read TBU with mfspr.

Reverting the patch solves the issue.

What's the prefered way to fix this ?

Christophe