[RFC] [PATCH] ARM: tegra: emc: device tree bindings

Olof Johansson wrote at Tuesday, October 18, 2011 2:54 PM:

On Tue, Oct 18, 2011 at 11:54 AM, Stephen Warren [off-list ref] wrote:

quoted

Olof Johansson wrote at Tuesday, October 18, 2011 12:43 PM:

...

quoted

quoted

Compatible is still needed, in my opinion -- otherwise there will be
no way to tell if the node is there to describe emc timings or if it's
some new node used to describe something else (such as SDRAM chips as
mentioned above).

Can't you go by node name; enumerate all nodes with a particular name.
Or define another intermediate node that will always contain tables and
nothing else, then just enumerate all child nodes of that node:

emc at xxxxx {
? ?emc-tables {
? ? ? ?table-333 at 0 {};
? ? ? ?table-666 at 0 {};
? ?};
};

The Tegra pinmux bindings I proposed certainly used this technique; a
main node with a well-known name, followed by enumeration of all child
nodes of that, and nobody /said/ anything about that being a bad idea.

I'm not really picky on this, but I think I would rather use a
compatible field than rely on naming.

That being said, doing a two-level approach will probably make it
easier than the flat structure I initially had. So:

emc at xxx {
    nvidia,use-ram-code;
    emc-table-ram-code-0 {
        nvidia,ram-code = < 0 >;
        table-166 { compatible = "tegra20-emc-table"; ... };
        table-333 { ... };
    };

    emc-table-ram-code-1 {
        nvidia,ram-code = < 1 >;
        ...
    };
};

... and for none-ram-code, just leave out the emc-table-ramcode-x level.

So, for nvidia,use-ram-code case, it'll be one intermediate step of
finding the right subnode, the rest of the table setup code will be
common. None of it will be bound to actual node names though -- first
step is iterating child nodes looking for nvidia,ram-code properties
to match, and second step iterates by matching compatible fields.

I only suggested the well-known-named sub-nodes in order to eliminate
the need for a compatible property.

My inclination is that if we use compatible to distinguish the tables
from anything else, there's little point having the extra level of nodes;
we may as well lay it out as in your original patch, just with an explicit
nvidia,ram-code property in each table (or omitted/ignored when not using
it) instead of reg?

-- 
nvpublic