linux-kernel - Re: [PATCH 2/7] mailbox: keembay-scmi-mailbox: Add support for Keem Bay mailbox

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Date:   Thu, 9 Jul 2020 14:28:10 +0100
From:   Paul Murphy <paul.j.murphy@...ux.intel.com>
To:     Daniele Alessandrelli <daniele.alessandrelli@...ux.intel.com>,
        Sudeep Holla <sudeep.holla@....com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        Rob Herring <robh+dt@...nel.org>,
        Jassi Brar <jassisinghbrar@...il.com>,
        Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>,
        Paul Murphy <paul.j.murphy@...el.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Dinh Nguyen <dinguyen@...nel.org>,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH 2/7] mailbox: keembay-scmi-mailbox: Add support for Keem
 Bay mailbox


On 7/9/20 13:23, Daniele Alessandrelli wrote:
> Hi Sudeep,
>
> Thanks for your review.
>
> On Wed, 2020-07-08 at 21:34 +0100, Sudeep Holla wrote:
>> On Tue, Jun 16, 2020 at 04:56:08PM +0100, Daniele Alessandrelli
>> wrote:
>>> From: Paul Murphy <paul.j.murphy@...el.com>
>>>
>>> Keem Bay SoC has a ARM trusted firmware-based secure monitor which
>>> acts
>>> as the SCP for the purposes of power management over SCMI.
>>>
>>> This driver implements the transport layer for SCMI to function.
>>>
>> Please use the smc transport support in
>> driver/firmware/arm_scmi/smc.c
>> for this. You don't need mailbox support for SMC/HVC. Basically you
>> don't need this driver at all and you have everything you need to
>> support
>> what you want.
>>
>> Let me know if you face issues.
>>
> Sorry, we didn't know about the SMC transport support for SCMI. Looks
> like it was added only recently, while our driver was already developed
> and waiting to be upstreamed.
>
> I agree that we can drop this driver and switch to the SMC transport as
> you suggested, but I think we'll have to modify our bootloader SiP
> service slightly. Paul, can you elaborate?
>

Just one question.

In our patch, we pass the shared memory address as the second argument 
of the SiP service, as it means we don't have to hardcode that in our 
firmware. Sudeep, do you know if it was intentional in 
smc_send_message() to leave that out? If we leave it out, we are 
requiring the secure monitor to hardcode the shared memory address.


Regards,
Paul