Re: [PATCH 0/6] mailbox: arm_mhu: add support to use in doorbell mode

[Jassi Brar]

On Thu, Jun 6, 2019 at 7:51 AM Sudeep Holla <sudeep.holla@xxxxxxx> wrote:

>
> > BTW, this is not going to be the end of SCMI troubles (I believe
> > that's what his client is). SCMI will eventually have to be broken up
> > in layers (protocol and transport) for many legit platforms to use it.
> > That is mbox_send_message() will have to be replaced by, say,
> > platform_mbox_send()  in drivers/firmware/arm_scmi/driver.c  OR  the
> > platforms have to have shmem and each mailbox controller driver (that
> > could ever be used under scmi) will have to implement "doorbell
> > emulation" mode. That is the reason I am not letting the way paved for
> > such emulations.
> >
>
> While I don't dislike or disagree with separate transport in SCMI which
> I have invested time and realised that I will duplicate mailbox framework
> at the end.
>
Can you please share the code? Or is it no more available?

> So I am against it only because of duplication and extra
> layer of indirection which has performance impact(we have this seen in
> sched governor for DVFS).
>
I don't see why the overhead should increase noticeably.

> So idea wise, it's good and I don't disagree
> with practically seen performance impact. Hence I thought it's sane to
> do something I am proposing.
>
Please suggest how is SCMI supposed to work on ~15 controllers
upstream (except tegra-hsp) ?

> It also avoids coming up with virtual DT
> nodes for this layer of abstract which I am completely against.
>
I don't see why virtual DT nodes would be needed for platform layer.