[PATCH v3 5/5] ARM: vexpress: DT-based support for CoreTiles Express A5x2 and A9x4

[dave.martin@linaro.org (Dave Martin)]

On Mon, Dec 05, 2011 at 05:47:36PM +0000, Pawel Moll wrote:
> On Mon, 2011-12-05 at 17:37 +0000, Dave Martin wrote:
> > > I have an idea of spinning the compatible values again to get something
> > > like that:
> > > 
> > > compatible = "arm,vexpress-v2p-ca5s", "arm,vexpress-cortex_a5";
> > > compatible = "arm,vexpress-v2p-ca9", "arm,vexpress-cortex_a9";
> > > compatible = "arm,vexpress-v2p-ca15", "arm,vexpress-cortex_a15";
> > 
> > The trouble is, node { compatible = x } means "node is an x", not "node
> > has an x".
> 
> Yes...
> 
> > So, we should be careful do document what e.g. arm,vexpress-cortex_a5
> > actually means.  It doesn't mean Cortex-A5, but instead it represents
> > a whole jumble of characteristics which we expect to be common to all
> > vexpress-based A5 platforms.
> 
> ... so I'd translate it as "is a Versatile Express platform based on
> Cortex-A5 processor" and document it as such. As I said - patches
> tomorrow.
> 
> > It feels that in practice arm,vexpress-cortex_a5 actually means 
> > exactly the same thing as arm,vexpress-v2p-ca5s.  Are you sure these
> > two are really independent?  (In other words, do we expect multiple
> > different vexpress variants based on A5, and so on?)
> 
> The examples for A5 I can quota are two different SMMs I used (one on a
> "small", second one on a "large" FPGA board), but they were very similar
> to the A5 core tile - so similar that you could (probably) use the core
> tile DTB to drive them. The A9 SMM with RS1 memory map I've mentioned is
> much more interesting case - A9 platform but nothing like original A9
> core tile... Also the A15 looks interesting as we will most likely get
> the same tiles (as in: PCB) with different processors (as in: different
> silicon). This will be fun :-)

OK -- your knowledge of what's going on in hardware-land is better than
mine, so I'm happy to go along with this.

So long as those compatible strings are carefully documented to that
their meanings don't get blurred over time, your proposal seems to make
sense.

Cheers
---Dave