linux-kernel - Re: [PATCH V3 2/2] firmware: arm

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Message-ID: <20200302112117.GB16218@e107533-lin.cambridge.arm.com>
Date:   Mon, 2 Mar 2020 11:21:17 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     Peng Fan <peng.fan@....com>
Cc:     "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "robh@...nel.org" <robh@...nel.org>,
        "viresh.kumar@...aro.org" <viresh.kumar@...aro.org>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        dl-linux-imx <linux-imx@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "andre.przywara@....com" <andre.przywara@....com>
Subject: Re: [PATCH V3 2/2] firmware: arm_scmi: add smc/hvc transport

On Sat, Feb 29, 2020 at 02:07:30AM +0000, Peng Fan wrote:
> Hi Sudeep,
>
> > Subject: Re: [PATCH V3 2/2] firmware: arm_scmi: add smc/hvc transport
> >
> > On Wed, Feb 26, 2020 at 03:12:51PM +0800, peng.fan@....com wrote:
> > > From: Peng Fan <peng.fan@....com>
> > >
> > > Take arm,smc-id as the 1st arg, and protocol id as the 2nd arg when
> > > issuing SMC/HVC. Since we need protocol id, so add this parameter
> >
> > And why do we need protocol id here ? I couldn't find it out myself.
> > I would like to know why/what/how is it used in the firmware(smc/hvc
> > handler). I hope you are not mixing the need for multiple channel with
> > protocol id ? One can find out id from the command itself, no need to pass it
> > and hence asking here for more details.
>
> When each protocol needs its own shmem area, we need let firmware
> know which shmem area to parse the message from. Without protocol
> id, firmware not know which shmem area should use. Hope this is clear.
>

Not all platforms need to have a separate shmem for each protocol. Make it
it separate transport.

--
Regards,
Sudeep