-----Original Message-----
From: Sudeep Holla [mailto:sudeep.holla@arm.com]
Sent: Tuesday, March 13, 2018 3:16 AM
To: Jolly Shah <redacted>
Cc: Sudeep Holla <redacted>; gregkh@linuxfoundation.org;
matt@codeblueprint.co.uk; hkallweit1@gmail.com; michal.simek@xilinx.com;
robh+dt@kernel.org; mark.rutland@arm.com; ard.biesheuvel@linaro.org;
mingo@kernel.org; keescook@chromium.org; dmitry.torokhov@gmail.com;
Rajan Vaja [off-list ref]; linux-arm-kernel@lists.infradead.org; linux-
kernel@vger.kernel.org; devicetree@vger.kernel.org
Subject: Re: [PATCH v5 1/4] dt-bindings: firmware: Add bindings for ZynqMP
firmware



On 12/03/18 23:07, Jolly Shah wrote:

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Hi Sudeep,

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Do you foresee using SMC/HVC for this firmware even on future

platforms?

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If not, I suggest to keep the protocol part separate from the transport i.e.
smc/hvc via ATF. It could be replaced with mailbox or some h/w
mechanism in future ?

We have PSCI and EEMI interfaces exposed to linux from ATF. PSCI is
an EEMI client. We do not have current plans to switch to mailbox as
it will require 2 communication channels to PMU as PSCI is through ATF.

OK, but I just saw some bindings that has mailbox interface, honestly
it's getting too confusing with multiple series on the same thing
floating and hence I requested to put it together as one series.

Mailbox binding is used for power management driver. Mailbox is only
used for PMU->APU communication. APU->PMU communication is always
through EEMI firmware interface which is using SMC/HVC.

Ah OK, is it because there's no non-secure mailbox or to avoid races, all non-
secure EEMI is channeled through SMC ?

2 reasons:
1> Avoid multiple EEMI communication channels as PSCI is through ATF.
2> We have some secure operations handled in ATF because of memory constraints on PMU

--
Regards,
Sudeep