From: Meador Inge <meador_inge@mentor•com>
To: Benjamin Herrenschmidt <benh@kernel•crashing.org>
Cc: Hollis Blanchard <hollis_blanchard@mentor•com>,
devicetree-discuss@lists•ozlabs.org,
linuxppc-dev@lists•ozlabs.org
Subject: Re: [PATCH v3 1/4] powerpc: Removing support for 'protected-sources'
Date: Sun, 06 Feb 2011 19:32:29 -0600 [thread overview]
Message-ID: <4D4F4BAD.4000909@mentor.com> (raw)
In-Reply-To: <1297035336.14982.14.camel@pasglop>
On 02/06/2011 05:35 PM, Benjamin Herrenschmidt wrote:
> On Fri, 2011-02-04 at 17:25 -0600, Meador Inge wrote:
>> In a recent thread [1,2,3] concerning device trees for AMP systems, the
>> question of whether we really need 'protected-sources' arose. The general
>> consensus was that a new boolean property 'pic-no-reset' (described in more
>> detail in a following patch) could be expanded to cover the use cases that
>> 'protected-sources' was covering.
>>
>> One concern that was raised was for legacy systems which already use the
>> 'protected-sources' property [4]. For legacy use cases, 'protected-sources'
>> will be treated as an alias of 'pic-no-reset'. The sources
>> encoded in the 'protected-sources' cells, however, will not be processed. This
>> legacy check is added in a later patch in the series.
>
> I'm a bit annoyed here. Why do we need to do that ? Those Cell machines
Apologies, that certainly was not the intent.
> are going to be real bastards to find and test with, and I don't really
> see the point...
The idea came up when submitting a patch for documenting an Open PIC
binding. The following two properties were documented in that binding:
(1) "protected-sources" and (2) "pic-no-reset". "pic-no-reset" is a
newly proposed property with the intent of specifying from a device tree
that the PIC should not be reset. The question of whether the one
property, "pic-no-reset", would suffice for both purposes came up.
It seems reasonable that "pic-no-reset" could satisfy the use case that
"protected-sources" is covering (since all of the sources that a
particular machine is actually using are already explicitly mentioned in
the device tree) and the use case of marking from a device tree that the
PIC should not be reset. So it is not so much as a need as it is a
potential simplification. It sounds like as a practical concern
(several systems using "protected-sources" are already in the wild and
testing considerations) that this may not be possible, which is fine.
> The reason for not resetting the MPIC wasn't -only- about the protected
> sources, but also because, from memory, some MPIC implementations had
> issues when toggling the reset lines (pseries I think is one).
>
> That's actually why the MPIC_WANTS_RESET flag is working the other way
> around, only platforms that actually want the reset set it.
>
> This is orthogonal to the need to touch or not touch the interrupt
> sources as set by firmware. Yes, having protected sources probably
> implies no-reset but the reverse isn't necessarily true.
So barring the removal of protected sources, does the inclusion of the
"pic-no-reset" property seem reasonable?
> Ben.
--
Meador Inge | meador_inge AT mentor.com
Mentor Embedded | http://www.mentor.com/embedded-software
next prev parent reply other threads:[~2011-02-07 1:32 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-04 23:25 [PATCH v3 0/4] powerpc: Open PIC binding and "pic-no-reset" Meador Inge
2011-02-04 23:25 ` [PATCH v3 1/4] powerpc: Removing support for 'protected-sources' Meador Inge
2011-02-06 23:35 ` Benjamin Herrenschmidt
2011-02-07 1:32 ` Meador Inge [this message]
2011-02-07 1:37 ` Benjamin Herrenschmidt
2011-02-07 18:02 ` Meador Inge
2011-02-07 21:45 ` Benjamin Herrenschmidt
2011-02-08 0:32 ` Meador Inge
2011-02-08 15:13 ` Yoder Stuart-B08248
2011-02-04 23:25 ` [PATCH v3 2/4] powerpc: document the Open PIC device tree binding Meador Inge
2011-02-04 23:25 ` [PATCH v3 3/4] powerpc: make MPIC honor the "pic-no-reset" device tree property Meador Inge
2011-02-04 23:25 ` [PATCH v3 4/4] powerpc: Replacing "protected-sources" with "pic-no-reset" in DTS files Meador Inge
[not found] ` <AANLkTinda9TX+Ng=kL-HHLOdqRnUZ6uitQKyZcRUHVco@mail.gmail.com>
2011-02-11 2:01 ` [PATCH v3 0/4] powerpc: Open PIC binding and "pic-no-reset" Meador Inge
2011-02-11 3:26 ` Meador Inge
2011-02-11 14:58 ` Yoder Stuart-B08248
2011-02-11 17:35 ` Meador Inge
2011-02-11 18:41 ` Scott Wood
2011-02-11 18:59 ` Grant Likely
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