Re: [PATCH] powerpc/fsl: add device tree binding for QE firmware

[Timur Tabi <timur@freescale.com>]

On Wed, Mar 24, 2010 at 1:07 AM, Grant Likely <grant.likely@secretlab.ca> w=
rote:

>> +- fsl,firmware-phandle:
>> + =A0 =A0Usage: required
>> + =A0 =A0Value type: <phandle>
>> + =A0 =A0Definition: Points to a firmware node (see "QE Firmware Node" b=
elow)
>> + =A0 =A0 =A0 =A0that contains the firmware that should be uploaded for =
this QE.
>> + =A0 =A0 =A0 =A0The compatible property for the firmware node should sa=
y,
>> + =A0 =A0 =A0 =A0"fsl,qe-firmware".
>> +
>
> Why the phandle redirection? =A0Why not just put the firmware blob into
> a property in the QE node, or as a subnode?

Because there might be multiple QE devices on a single chip, and each
will need to upload the same firmware.  So instead of embedding the
firmware multiple times, just embed it once, and have a pointer.

I could expand the binding to say that a node should look for either
fsl,firmware-phandle *or* a child fsl,qe-firmware node, but I think
that overly complicates things.  It also makes it more complicated for
the boot loader to create the fsl,qe-firmware node, since it has to
figure out where to put that node.  I can imaging a situation where
the DTS has the fsl,firmware-phandle properties and an empty
fsl,qe-firmware node at the root, and the boot loader just fills it
in.

--=20
Timur Tabi
Linux kernel developer at Freescale