[PATCH v3 1/4] powerpc: Removing support for 'protected-sources'
meador_inge at mentor.com
Tue Feb 8 11:32:39 EST 2011
On 02/07/2011 03:45 PM, Benjamin Herrenschmidt wrote:
>> In my previous reply I said that "it is not so much as a need as it is a
>> potential simplification." After further reflection, I don't think that
>> is completely true. As we get into AMP systems with higher core counts,
>> then implementing this functionality using the existing
>> "protected-sources" implementation versus the new "pic-no-reset" work is
>> going to be harder to maintain.
> I'm not arguing that your approach isn't more suitable for AMP systems,
> I just want to leave the existing protected-sources mechanism alone. I'm
> not opposing adding a new, better, mechanism for newer platforms.
Is the mechanism mentioned earlier of having "protected-sources" as a
synonym for "pic-no-reset" not suitable? Or would you like the current
protected sources implementation left completely intact?
> However, I'd name it differently. "pic-no-reset" doesn't carry enough
> meaning in that case. What we want to point out here is that the PIC
> has been pre-initialized.
> Another option, which may be cleaner, is to stick to "no-reset" (no need
> for pic- prefix) and make it do just that (prevent the reset), and then
It originally was "no-reset", but that was considered too broad.  :)
> use a positive variant of "protected-sources", call it
> "allowed-sources". Maybe even make it a series of ranges. Then have the
> MPIC only access these.
That would work, but I still don't like having to mention this
information twice in the device tree. All the sources encoded in the
various "interrupts" properties _are_ the allowed sources, right?
> I think this is more robust as it would also prevent "accidental" use of
> the wrong sources (bad device-tree, drivers that let you muck around
> with irq numbers, etc...).
That would be nice. All though, it may not be as helpful as it sounds.
There is as much of a risk that someone will botch the
"allowed-sources" property as there is they will botch the "interrupts"
property. We could perhaps still preform these checks without the extra
property: if a source is not mentioned in an interrupts property, then
it is not allowed.
Meador Inge | meador_inge AT mentor.com
Mentor Embedded | http://www.mentor.com/embedded-software
More information about the Linuxppc-dev