[U-Boot] [PATCH 2/2] sun7i: Add PSCI v0.2 support

[Ian Campbell]

On Wed, 2014-12-31 at 12:57 +0100, Jan Kiszka wrote:
> On 2014-12-29 15:12, Ian Campbell wrote:
> > On Mon, 2014-12-15 at 12:37 +0100, Jan Kiszka wrote:
> >> This extends the PSCI support for the A20 to a dual v0.2 and v0.1
> >> interface. Recent OSes will prefer v0.2, olders will still find the
> >> original interface, just at v0.2 service IDs.
> >>
> >> In addition to the existing services, v0.2 requires us to implement both
> >> system off and reset. At least Linux will make use of them in favor of
> >> its own implementations and, thus, fail if they do not work.
> > 
> > What functionality does v0.2 give us over v0.1 that you are aiming to
> > expose here?
> 
> For us, the added value is currently in next layer: we can simplify the
> Jailhouse hypervisor a bit when leaving out v0.1 support right from the
> beginning. But that means U-Boot has to support v0.2 on the platforms we
> target at.

Understood, although we support both with Xen and it's really not very
much code.

> v0.2 is the current standard, so I would expect new boards to use that
> one in the future by default.

Given the extra complexity of v0.2 vs v0.1 for the firmware, and the
lack of compelling new features added by v0.2 for platforms which don't
run anything in secure world, I'm not sure that's a given. Indeed, that
was the thrust of my original question...

Ian.