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Message-ID: <53105E8E.1040504@gmail.com> Date: Fri, 28 Feb 2014 11:01:50 +0100 From: Tomasz Figa <tomasz.figa@...il.com> To: Marek Szyprowski <m.szyprowski@...sung.com>, Grant Likely <grant.likely@...aro.org>, 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: Benjamin Herrenschmidt <benh@...nel.crashing.org>, Arnd Bergmann <arnd@...db.de>, Michal Nazarewicz <mina86@...a86.com>, Tomasz Figa <t.figa@...sung.com>, Sascha Hauer <s.hauer@...gutronix.de>, Laura Abbott <lauraa@...eaurora.org>, Rob Herring <robh+dt@...nel.org>, 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>, Kumar Gala <galak@...eaurora.org>, Nishanth Peethambaran <nishanth.p@...il.com>, Marc <marc.ceeeee@...il.com>, Josh Cartwright <joshc@...eaurora.org>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will.deacon@....com>, Paul Mackerras <paulus@...ba.org> Subject: Re: [PATCH v5 01/11] of: document bindings for reserved-memory nodes On 28.02.2014 10:54, Marek Szyprowski wrote: > Hello, > > On 2014-02-26 12:51, Grant Likely wrote: >> On Fri, 21 Feb 2014 13:25:17 +0100, Marek Szyprowski >> <m.szyprowski@...sung.com> wrote: >> > From: Grant Likely <grant.likely@...aro.org> >> > >> > Reserved memory nodes allow for the reservation of static (fixed >> > address) regions, or dynamically allocated regions for a specific >> > purpose. >> > >> > Signed-off-by: Grant Likely <grant.likely@...aro.org> >> > [joshc: Based on binding document proposed (in non-patch form) here: >> > >> http://lkml.kernel.org/g/20131030134702.19B57C402A0@trevor.secretlab.ca >> > adapted to support #memory-region-cells] >> > Signed-off-by: Josh Cartwright <joshc@...eaurora.org> >> > Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com> >> > --- >> > .../bindings/reserved-memory/reserved-memory.txt | 138 >> ++++++++++++++++++++ >> > 1 file changed, 138 insertions(+) >> > create mode 100644 >> Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt >> > >> > diff --git >> a/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt b/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt >> >> > new file mode 100644 >> > index 000000000000..a606ce90c9c4 >> > --- /dev/null >> > +++ >> b/Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt >> > @@ -0,0 +1,138 @@ >> > +*** Reserved memory regions *** >> > + >> > +Reserved memory is specified as a node under the /reserved-memory >> node. >> > +The operating system shall exclude reserved memory from normal usage >> > +one can create child nodes describing particular reserved (excluded >> from >> > +normal use) memory regions. Such memory regions are usually >> designed for >> > +the special usage by various device drivers. >> > + >> > +Parameters for each memory region can be encoded into the device tree >> > +with the following nodes: >> > + >> > +/reserved-memory node >> > +--------------------- >> > +#address-cells, #size-cells (required) - standard definition >> > + - Should use the same values as the root node >> > +#memory-region-cells (required) - dictates number of cells used in >> the child >> > + nodes memory-region specifier >> >> I still don't like this portion of the binding. I'm not convinced that >> it is necessary in the majority of cases and it is going to be very >> driver specific. I would rather drop it entirely from the common >> binding. If a specific driver needs to do something like the above then >> it can have a driver specific binding. Otherwise I think the default >> should be a simple phandle with no arguments to a single reserved memory >> node. >> >> Ben, can you weigh in on the current state of this document. I'm mostly >> happy with it aside from my comment above. Do you think this is ready to >> be merged? >> >> > +ranges (required) - standard definition >> > + - Should be empty >> > + >> > +/reserved-memory/ child nodes >> > +----------------------------- >> > +Each child of the reserved-memory node specifies one or more >> regions of >> > +reserved memory. Each child node may either use a 'reg' property to >> > +specify a specific range of reserved memory, or a 'size' property with >> > +optional constraints to request a dynamically allocated block of >> memory. >> > + >> > +Following the generic-names recommended practice, node names should >> > +reflect the purpose of the node (ie. "framebuffer" or "dma-pool"). >> Unit >> > +address (@<address>) should be appended to the name if the node is a >> > +static allocation. >> > + >> > +Properties: >> > +Requires either a) or b) below. >> > +a) static allocation >> > + reg (required) - standard definition >> > +b) dynamic allocation >> > + size (required) - length based on parent's #size-cells >> > + - Size in bytes of memory to reserve. >> > + alignment (optional) - length based on parent's #size-cells >> > + - Address boundary for alignment of >> allocation. >> > + alloc-ranges (optional) - prop-encoded-array (address, length >> pairs). >> > + - Specifies regions of memory that are >> > + acceptable to allocate from. >> > + >> > +If both reg and size are present, then the reg property takes >> precedence >> > +and size is ignored. >> > + >> > +Additional properties: >> > +compatible (optional) - standard definition >> > + - may contain the following strings: >> > + - shared-dma-pool: This indicates a region of memory meant >> to be >> > + used as a shared pool of DMA buffers for a set of >> devices. It can >> > + be used by an operating system to instanciate the >> necessary pool >> > + management subsystem if necessary. >> > + - vendor specific string in the form >> <vendor>,[<device>-]<usage> >> >> Add "Use vendor strings to identify regions dedicates for a specific >> vendor device. For example: 'acme,framebuffer'. Platform code can use >> vendor >> strings to identify device specific regions" > > So do you want to completely drop phandle based links between device > nodes and > memory regions? Huh? How this would work with regions that have to be used for multiple (but not all - not a default region) devices? Best regards, Tomasz -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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