linux-kernel - Re: [PATCHv5 RFC 12/15] hwspinlock/core: add OF helper to parse reserved locks

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Date:	Mon, 5 May 2014 16:54:22 -0500
From:	Josh Cartwright <joshc@...eaurora.org>
To:	Suman Anna <s-anna@...com>
Cc:	Ohad Ben-Cohen <ohad@...ery.com>,
	Mark Rutland <mark.rutland@....com>,
	Kumar Gala <galak@...eaurora.org>,
	Rob Herring <robherring2@...il.com>,
	Tony Lindgren <tony@...mide.com>,
	Josh Cartwright <joshc@...eaurora.org>,
	Bjorn Andersson <bjorn@...o.se>, linux-kernel@...r.kernel.org,
	linux-omap@...r.kernel.org, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCHv5 RFC 12/15] hwspinlock/core: add OF helper to parse
 reserved locks

On Mon, May 05, 2014 at 04:44:25PM -0500, Suman Anna wrote:
> Hi Rob,
> 
> On 04/30/2014 07:34 PM, Suman Anna wrote:
> > The property 'hwlock-reserved-locks' will be used to represent
> > the number of locks to be reserved for clients that would need
> > to request/operate on specific locks. A new OF helper function,
> > of_hwspin_lock_get_num_reserved_locks(), is added to minimize
> > duplication in different platform implementations.
> > 
> > The function will return a value of 0 if the property is not
> > defined, so as to support a default behavior of marking all
> > locks as unused and open for anonymous allocations.
> > 
> > Signed-off-by: Suman Anna <s-anna@...com>
> > ---
> >  .../devicetree/bindings/hwlock/hwlock.txt          |  3 +++
> >  drivers/hwspinlock/hwspinlock_core.c               | 25 ++++++++++++++++++++++
> >  include/linux/hwspinlock.h                         |  1 +
> >  3 files changed, 29 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/hwlock/hwlock.txt b/Documentation/devicetree/bindings/hwlock/hwlock.txt
> > index d538a9b..88d16d2 100644
> > --- a/Documentation/devicetree/bindings/hwlock/hwlock.txt
> > +++ b/Documentation/devicetree/bindings/hwlock/hwlock.txt
> > @@ -18,6 +18,9 @@ Common properties:
> >  			property is needed on hwlock devices, where the number
> >  			of supported locks within a hwlock device cannot be
> >  			read from a register.
> > +- hwlock-reserved-locks: Number of locks to reserve for clients requiring
> > +			specific locks. This value cannot exceed the value of
> > +			hwlock-num-locks.
> 
> Any suggestions here on the approach? This property falls into a gray
> area as well, as the current approach is somewhat limiting (it doesn't
> support sparse reserved locks, and expects them at the beginning of the
> lock range).

Is it possible to implement a pinctrl-like hogging approach, whereby the
specific locks that need to be reserved are consumed by the controller
itself?

  Josh

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