[PATCHv2] powerpc: Describe memory-mapped RAM&ROM chips OF bindings

[Laurent Pinchart]

On Tuesday 01 April 2008 15:16, Grant Likely wrote:
> On Mon, Mar 31, 2008 at 10:39 AM, Laurent Pinchart
> <laurentp at cse-semaphore.com> wrote:
> >
> >  Signed-off-by: Laurent Pinchart <laurentp at cse-semaphore.com>
> >  ---
> >   Documentation/powerpc/booting-without-of.txt |   13 ++++++++++++-
> >   1 files changed, 12 insertions(+), 1 deletions(-)
> >
> >  diff --git a/Documentation/powerpc/booting-without-of.txt 
> >  b/Documentation/powerpc/booting-without-of.txt 
> >  index 7b4e8a7..3e1963b 100644
> >  --- a/Documentation/powerpc/booting-without-of.txt
> >  +++ b/Documentation/powerpc/booting-without-of.txt
> >  @@ -57,7 +57,8 @@ Table of Contents
> >        n) 4xx/Axon EMAC ethernet nodes
> >        o) Xilinx IP cores
> >        p) Freescale Synchronous Serial Interface
> >  -         q) USB EHCI controllers
> >  +      q) USB EHCI controllers
> >  +      r) Memory-mapped RAM & ROM
> >
> >    VII - Specifying interrupt information for devices
> >      1) interrupts property
> >  @@ -2816,6 +2817,16 @@ platforms are moved over to use the
> >  flattened-device-tree model. 
> >                    big-endian;
> >            };
> >
> >  +   r) Memory-mapped RAM & ROM
> >  +
> >  +    Dedicated RAM and ROM chips are often used as storage for temporary
> >  or 
> >  +    permanent data in embedded devices. Possible usage include
> >  non-volatile 
> >  +    storage in battery-backed SRAM, semi-permanent storage in dedicated
> >  SRAM 
> >  +    to preserve data accross reboots and firmware storage in dedicated
> >  ROM. 
> >  +
> >  +     - name : should be either "ram" or "rom"
> >  +     - reg : Address range of the RAM/ROM chip
> >  +
> 
> No compatible prop?  How does the OS know what the node is to be used for?

If I understood Sergei's arguments properly, the device tree should describe 
device properties and not their intended usage. With generic devices such as 
RAM chips, platform code is responsible for binding the device to the 
appropriate driver (mtd-ram for instance).

Cheers,

-- 
Laurent Pinchart
CSE Semaphore Belgium

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