Re: Device tree bindings for linux ramoops use

[Mitch Bradley <wmb-D5eQfiDGL7eakBO8gow8eQ@public.gmane.org>]

On 1/5/2012 6:39 PM, Olof Johansson wrote:
> Hi,
>
> I'm considering how to best describe the data that ramoops needs in
> the device tree.
>
> The idea is really about describing a memory area that is (likely to
> be) nonvolatile across reboots. Said area is not to be included in the
> regular memory map of the system (i.e. not covered by /memory).
>
> I have a few options on where to do it. It's not really a hardware
> device per se, so it's a gray area for the device tree alltogether.
>
> How about something like?
>
> compatible = "linux,ramoops"
> linux,ramoops-start =<start address of preserved ram>
> linux,ramoops-size = ...
> linux,ramoops-record-size = ...
> linux,ramoops-include-oopses = ... (this one is a bit of a corner
> case, it's truly a software setting -- probably leave it out)
>
> Anybody have a better idea?

If it is addressable, it should appear as a device node underneath the 
node that creates the address space in which it appears, and the start 
and size should be described by a "reg" property.

>
> I could do a platform-specific binding that describes the nonvolatile
> ram area as a separate "device", and then have some platform code that
> translates that into the ramoops platform pdata parameters (since it
> can't really be assumed that ramoops has ownership of the whole
> area/device). That seems pretty awkward too though, and I'm not sure
> it buys us a whole lot.
>
>
> -Olof
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