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

Arnd Bergmann wrote:

What does the firmware node contain then? The way I read it, you only put
metadata about the uploaded firmware in there, but not the blob itself, right?

That's correct.  The meta-data is only the information that a device driver 
would need to identify and interact with the microcode.

Is there a case where you don't need the firmware in order to start the
kernel, but still want to provide it in flash?

I don't think you'll ever need the firmware to *start* the kernel.

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.

That would require the firmware to present in RAM for all time, since the device 
tree cannot be unloaded.  Besides, you might need to have the firmware loaded in 
U-Boot anyway.  If your console is connected to the QE, then you'll need the 
UART firmware loaded before you can see anything.  That's why U-Boot needs its 
own version.

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.

Technically, the firmware could be considered a device on the QE, because it's 
loaded into I-RAM and it can significantly alter the behavior of the device. 
Having it its own node also lets me compartmentalize it.  If I want to expand 
the node and add more properties, it's cleaner.

-- 
Timur Tabi
Linux kernel developer at Freescale