Re: [U-Boot] [RFC] Kbuild support for ARM FIT images

Jason Gunthorpe
2013-02-21T23:28:34Z

On Fri, Feb 22, 2013 at 12:18:48AM +0100, Wolfgang Denk wrote:

> > The DT is meant to describe hardware. As far as I know, the hardware I
> > own seems to be rather static and stable, and unlike software there is
> > no way I can change it (soldering irons don't count).
>
> There is other hardware available (for example FPGA based) where this
> does not apply.

Agreed.. We do that here as well, the DT is also used to describe the
functionality inside FPGA(s). We do things like declare a GPIO
controller inside the FPGA, then stack the bitbang MDIO/I2C on top of
that, then declare a bunch of devices on those busses. DT makes this
extremely straightforward.

However, it is critical that the DT, kernel and FPGA are matched
together - we always arrange things so that the DTB, kernel and FPGA
config are bundled together and update atomically during firmware
upgrade.

Xilinx's Zynq is a great example of this kind of stuff, FWIW. IIRC
Xilinx has a DT generator from their IP tools, so you can literally go
into their design software, configure the hardware IP blocks, and get
back a FPGA config and a DT to go with it.

Jason