linux-kernel - Re: [PATCH v11 2/2] mailbox: introduce ARM SMC based mailbox

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Date:   Tue, 28 Jan 2020 11:38:21 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     Peng Fan <peng.fan@....com>
Cc:     Etienne Carriere <etienne.carriere@...aro.org>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "andre.przywara@....com" <andre.przywara@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        etienne carriere <etienne.carriere@...com>,
        Sudeep Holla <sudeep.holla@....com>
Subject: Re: [PATCH v11 2/2] mailbox: introduce ARM SMC based mailbox

On Mon, Jan 27, 2020 at 12:58:12PM +0000, Peng Fan wrote:
> > Subject: Re: [PATCH v11 2/2] mailbox: introduce ARM SMC based mailbox
> >
> > Hello Peng and all,
> > > From: Peng Fan <peng.fan@....com>
> > >
> > > This mailbox driver implements a mailbox which signals transmitted
> > > data via an ARM smc (secure monitor call) instruction. The mailbox
> > > receiver is implemented in firmware and can synchronously return data
> > > when it returns execution to the non-secure world again.
> > > An asynchronous receive path is not implemented.
> > > This allows the usage of a mailbox to trigger firmware actions on SoCs
> > > which either don't have a separate management processor or on which
> > > such a core is not available. A user of this mailbox could be the SCP
> > > interface.
> > >

[...]

> > I've successfully tested your change on my board. It is a stm32mp1 with TZ
> > secure hardening and I run an OP-TEE firmware (possibly a TF-A
> > sp_min) with a SCMI server for clock and reset. Upstream in progress.
> > The platform uses 2 instances of your SMC based mailbox device driver
> > (2 mailboxes). Works nice with your change.
> >
> > You can add my T-b tag: Tested-by: Etienne Carriere
> > <etienne.carriere@...aro.org>
>
> Thanks, but this patch has been dropped.
>
> Per Sudeep, we all use smc transport, not smc mailbox ,
>
Yes, I asked if there are any other users of SMC mailbox other than
SCMI. We are planning to separate the transport from the SCMI driver[1]
to enable transport other than mailbox. SMC can be one of them and the
other one planned is virtio. Please feel free to add to the discussion
or review.

--
Regards,
Sudeep

[1] https://lore.kernel.org/lkml/f170b33989b426ac095952634fcd1bf45b86a7a3.1580208329.git.viresh.kumar@linaro.org