linux-kernel - Re: [PATCH v2 1/5] drivers: of: add initialization code for reserved memory

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Date:	Tue, 11 Feb 2014 19:01:04 +0000
From:	Grant Likely <grant.likely@...aro.org>
To:	Tomasz Figa <t.figa@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linaro-mm-sig@...ts.linaro.org, devicetree@...r.kernel.org,
	linux-doc@...r.kernel.org
Cc:	Kyungmin Park <kyungmin.park@...sung.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Arnd Bergmann <arnd@...db.de>,
	Michal Nazarewicz <mina86@...a86.com>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Laura Abbott <lauraa@...eaurora.org>,
	Rob Herring <robh+dt@...il.com>,
	Olof Johansson <olof@...om.net>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Stephen Warren <swarren@...dotorg.org>,
	Ian Campbell <ian.campbell@...rix.com>,
	Tomasz Figa <tomasz.figa@...il.com>,
	Kumar Gala <galak@...eaurora.org>,
	Nishanth Peethambaran <nishanth.p@...il.com>,
	Marc <marc.ceeeee@...il.com>,
	Josh Cartwright <joshc@...eaurora.org>
Subject: Re: [PATCH v2 1/5] drivers: of: add initialization code for reserved memory

On Tue, 11 Feb 2014 15:29:54 +0100, Tomasz Figa <t.figa@...sung.com> wrote:
> > Yes, if only because it is an define usage of the reg property. If a
> > devtree has multiple tuples in reg, then all of those tuples should be
> > treated as reserved, even if the kernel doesn't know how to use them.
> >
> > I would not do the same for size/align/alloc-ranges unless there is a
> > very specific use case that you can define. These ones are different
> > from the static regions because they aren't ever used to protect
> > something that already exists in the memory.
> 
> Is there a reason why multiple regions could not be used for this 
> purpose, instead of adding extra complexity of having multiple reg 
> entries per region?
> 
> I.e. I don't see a difference between
> 
> reg1: region@...00000 {
> 	reg = <0x00000000 0x1000>;
> };
> 
> reg2: region@...00000 {
> 	reg = <0x10000000 0x1000>;
> };
> 
> user {
> 	regions = <&reg1>, <&reg2>;
> };
> 
> and
> 
> reg: region@...00000 {
> 	reg = <0x00000000 0x1000>, <0x10000000 0x1000>;
> };
> 
> user {
> 	regions = <&reg>;
> };
> 
> except that the former IMHO better suits the definition of memory 
> region, which I see as a single contiguous range of memory and can be 
> simplified to have a single reg entry per region.

My point is rather if multiple reg tuples are found in a reserved memory
node, the kernel must respect them and reserve the memory. I'm not
arguing about whether or not that makes for a good binding.

g.

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