[PATCH v3 1/4] powerpc: Removing support for 'protected-sources'
B08248 at freescale.com
Wed Feb 9 02:13:13 EST 2011
> -----Original Message-----
> From: devicetree-discuss-
> bounces+stuart.yoder=freescale.com at lists.ozlabs.org [mailto:devicetree-
> discuss-bounces+stuart.yoder=freescale.com at lists.ozlabs.org] On Behalf Of
> Benjamin Herrenschmidt
> Sent: Monday, February 07, 2011 3:46 PM
> To: Meador Inge
> Cc: Hollis Blanchard; devicetree-discuss at lists.ozlabs.org; linuxppc-
> dev at lists.ozlabs.org
> Subject: Re: [PATCH v3 1/4] powerpc: Removing support for 'protected-
> > 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.
> 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 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.
> 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...).
What is the use case for "allowed-sources"? For AMP the only device
nodes in your device tree should be your AMP partition's devices,
thus any interrupt specifiers in your dev tree are "allowed".
The MPIC is a shared device and thus the need for no-reset.
So, all newer platforms should need is "no-reset".
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