Message-ID: <52FA87B8.8040203@gmail.com>
Date: Tue, 11 Feb 2014 21:27:36 +0100
From: Tomasz Figa <tomasz.figa@gmail.com>
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To: Josh Cartwright <joshc@codeaurora.org>
CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Grant Likely <grant.likely@linaro.org>,
        Tomasz Figa <t.figa@samsung.com>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linaro-mm-sig@lists.linaro.org, devicetree@vger.kernel.org,
        linux-doc@vger.kernel.org, Kyungmin Park <kyungmin.park@samsung.com>,
        Arnd Bergmann <arnd@arndb.de>, Michal Nazarewicz <mina86@mina86.com>,
        Sascha Hauer <s.hauer@pengutronix.de>,
        Laura Abbott <lauraa@codeaurora.org>, Rob Herring <robh+dt@gmail.com>,
        Olof Johansson <olof@lixom.net>, Pawel Moll <pawel.moll@arm.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Stephen Warren <swarren@wwwdotorg.org>,
        Ian Campbell <ian.campbell@citrix.com>,
        Kumar Gala <galak@codeaurora.org>,
        Nishanth Peethambaran <nishanth.p@gmail.com>,
        Marc <marc.ceeeee@gmail.com>
Subject: Re: [PATCH v2 1/5] drivers: of: add initialization code for reserved
 memory
References: <1391515773-6112-1-git-send-email-m.szyprowski@samsung.com> <1391515773-6112-2-git-send-email-m.szyprowski@samsung.com> <20140205110538.99E47C40A89@trevor.secretlab.ca> <52FA0D6E.9090304@samsung.com> <20140211121316.24032C40C4D@trevor.secretlab.ca> <52FA33E2.4050004@samsung.com> <20140211190104.7E6C5C4140E@trevor.secretlab.ca> <1392148971.3835.15.camel@pasglop> <52FA8245.5050707@gmail.com> <20140211201933.GI841@joshc.qualcomm.com>
In-Reply-To: <20140211201933.GI841@joshc.qualcomm.com>
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On 11.02.2014 21:19, Josh Cartwright wrote:
> On Tue, Feb 11, 2014 at 09:04:21PM +0100, Tomasz Figa wrote:
>>
>>
>> On 11.02.2014 21:02, Benjamin Herrenschmidt wrote:
>>> On Tue, 2014-02-11 at 19:01 +0000, Grant Likely wrote:
>>>
>>>>> 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.
>>>
>>> agreed.
>>
>> My point is why, if the binding defines that just a single tuple should be
>> provided.
>
> FWIW, the usecase I had mentioned in reply to Grant in the patch 5/5
> thread [1] could make use of this.  The shared memory region is split
> into a main chunk and several "auxiliary" chunk, but collectively these
> regions all share the same heap state.
>
>    Josh
>
> 1: http://lkml.kernel.org/r/20140205192502.GO20228@joshc.qualcomm.com
>

The use case seems fine, but I believe it could be properly represented 
in device tree using multiple single-reg regions as well, unless the 
consumer can request a block of memory that crosses boundary of two 
sub-regions specified by reg entries of single region.

Best regards,
Tomasz
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