Re: [PATCH v2] qe: add ability to upload QE firmware

[Arnd Bergmann <arnd@arndb.de>]

On Thursday 06 December 2007, Timur Tabi wrote:
> > In that case, I think it
> > would really be better to just put the blob into the tree and only
> > have the fw loading code in the kernel instead of duplicating it in the=
 boot
> > loader.
>=20
> That would require the firmware to present in RAM for all time, since the=
 device=20
> tree cannot be unloaded.

Yes, that's a backdraw of my approach, but in the case of spidernet, it was=
 only
an insignificant amount of RAM. Don't know what sizes of RAM and QE firmware
to expect typically on the machines you care about.

> Besides, you might need to have the firmware loaded in =20
> U-Boot anyway. =A0If your console is connected to the QE, then you'll nee=
d the=20
> UART firmware loaded before you can see anything. =A0That's why U-Boot ne=
eds its=20
> own version.

Right, so you can't really get around having it in some boot loaders at lea=
st.
IIRC you said that the firmware is only needed for serial output on some ch=
ips
but not on others. What about the case where you don't need it for serial b=
ut
still want to provide it by the firmware, and perhaps use something other t=
han
U-boot? Is that relevant?

I'm not trying to convince you of this if it's completely pointless for
all your systems, just want to make sure you're aware of this option,
because spending a few extra code lines on it now may save you some trouble
if you need this later.

> > Regarding the question whether the firmware should be a device node or
> > a property of another node, I'd prefer a simple property, because the
> > firmware itself is not really a device you can access, but I don't care
> > much about that.
>=20
> Technically, the firmware could be considered a device on the QE, because=
 it's=20
> loaded into I-RAM and it can significantly alter the behavior of the devi=
ce.=20

Well, it doesn't have any of the standard properties like registers or inte=
rrupts
though.

> Having it its own node also lets me compartmentalize it. =A0If I want to =
expand=20
> the node and add more properties, it's cleaner.

Yes, that makes a lot of sense.

	Arnd <><