Re: [PATCH v5 1/2] dt-bindings: mailbox: add binding doc for the ARM SMC/HVC mailbox

From: Sudeep Holla
Date: Fri Aug 30 2019 - 05:30:14 EST

On Fri, Aug 30, 2019 at 07:37:41AM +0000, Peng Fan wrote:
> Hi Jassi,
> > > I think there could be channel for TEE, and channel for Linux.
> > > For virtualization case, there could be dedicated channel for each VM.
> > >
> > I am talking from Linux pov. Functions 0xfe and 0xff above, can't both be
> > active at the same time, right?
> If I get your point correctly,
> On UP, both could not be active. On SMP, tx/rx could be both active, anyway
> this depends on secure firmware and Linux firmware design.

Just to confirm, we can't have SMC/HVC based Rx channel as there's no
*architectural* way to achieve it. So it can be based on some interrupt
from secure side and hence will be a *different* type of channel/controller.

Sorry to make this point repeatedly, but juts to be absolutely clear:
as it stands, SMC/HVC can be used only for Tx today.