questions on CONFIG_PPC_ADV_DEBUG_REGS, DBCR0_BRT, and DBCR0_ACTIVE_EVENTS

[Scott Wood]

On Tue, 2014-04-22 at 05:43 -0700, shiva7 wrote:
> I have the same question as like above posted by Mr. Chirs. 

I had to google the subject to find what e-mail you were talking about
-- it was posted a year ago:

http://marc.info/?l=linuxppc-embedded&m=136572252330650&w=2

Next time please quote the e-mail if you're trying to revive a thread,
and keep the original poster on CC.

I've quoted it here:

> Sorry for the bunch of emails, I'm working on some new stuff and running 
> into issues.
> 
> For CONFIG_BOOKE it appears that DBCR0_ACTIVE_EVENTS includes DBCR0_ICMP 
> but not DBCR0_BRT.  Is that just because none of the code paths 
> currently using DBCR0_ACTIVE_EVENTS need to check DBCR0_BT?

Perhaps it was just an oversight.  I've CCed Dave Kleikamp and Torez
Smith, who added DBCR0_ACTIVE_EVENTS.

> Also, in sys_debug_setcontext() why does SIG_DBG_BRANCH_TRACING return 
> -EINVAL if CONFIG_PPC_ADV_DEBUG_REGS is set?  Would it not be possible 
> to use DBCR0_BRT?

Either nobody has gotten around to implementing it, or the semantics
are different in some way (if the semantics are even defined anywhere
-- I couldn't find any documentation).

-Scott