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

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Date:   Wed, 22 Jan 2020 19:20:01 +0100
From:   Etienne Carriere <etienne.carriere@...aro.org>
To:     Peng Fan <peng.fan@....com>, f.fainelli@...il.com,
        andre.przywara@....com, linux-kernel@...r.kernel.org,
        etienne carriere <etienne.carriere@...com>
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.
>
> Modified from Andre Przywara's v2 patch
> https://lore.kernel.org/patchwork/patch/812999/
>
> Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
> Reviewed-by: Andre Przywara <andre.przywara@....com>
> Signed-off-by: Peng Fan <peng.fan@....com>

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>

FYI, I'll (hopefully soon) post a change proposal in U-Boot ML for an
equvalent 'SMC based mailbox' driver and SCMI agent protocol/device
drivers for clock and reset controllers.
I'm also working on getting this SCMI server upstream in TF-A and
OP-TEE. Your SMC based mailbox driver is a valuable notification
scheme for our SCMI services support in Arm TZ secure world.

Regards,
Etienne