linux-kernel - Re: [PATCH V2] firmware: arm_scmi: Make scmi core independent of transport type

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Date:   Wed, 15 Jan 2020 14:33:25 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     Peng Fan <peng.fan@....com>
Cc:     Viresh Kumar <viresh.kumar@...aro.org>,
        "arnd@...db.de" <arnd@...db.de>,
        "jassisinghbrar@...il.com" <jassisinghbrar@...il.com>,
        "cristian.marussi@....com" <cristian.marussi@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH V2] firmware: arm_scmi: Make scmi core independent of
 transport type

On Wed, Jan 15, 2020 at 08:53:51AM +0000, Peng Fan wrote:
>
> > Subject: [PATCH V2] firmware: arm_scmi: Make scmi core independent of
> > transport type
> >
> > The SCMI specification is fairly independent of the transport protocol, which
> > can be a simple mailbox (already implemented) or anything else.
> > The current Linux implementation however is very much dependent of the
> > mailbox transport layer.
> >
> > This patch makes the SCMI core code (driver.c) independent of the mailbox
> > transport layer and moves all mailbox related code to a new
> > file: mailbox.c.
> >
> > We can now implement more transport protocols to transport SCMI messages,
> > some of the transport protocols getting discussed currently are SMC/HVC,
> > SPCI (built on top of SMC/HVC), OPTEE based mailbox (similar to SPCI), and
> > vitio based transport as alternative to mailbox.
> >
> > The transport protocols just need to provide struct scmi_desc, which also
> > implements the struct scmi_transport_ops.
>
> I need put shmem for each protocol, is this expected?

No, it's optional. If some/all protocols need dedicated channel for whatever
reasons(like DVFS/Perf for polling based transfers), they can specify.
Absence of dedicated channel infers all protocols share the channel(s).

> Sudeep,
> I am able to use smc to directly transport data,
> with adding a new file, just named smc.c including a scmi_smc_desc,

Good.

> But I not find a good way to pass smc id to smc transport file.
>

IMO, we have to deal this in transport specific init. I am thinking of
chan_setup in context of this patch. Does that make sense ?

[...]

> +
> +    scmi_clk: protocol@14 {
> +            reg = <0x14>;
> +            shmem = <&cpu_scp_lpri>;
> +            #clock-cells = <1>;
> +            clocks = <&osc_32k>, <&osc_24m>, <&clk_ext1>, <&clk_ext2>,
> +                     <&clk_ext3>, <&clk_ext4>;
> +            clock-names = "osc_32k", "osc_24m", "clk_ext1", "clk_ext2",
> +                          "clk_ext3", "clk_ext4";

This caught my attention, why do we need these clocks phandle list and
clock names above ? Ideally just need scmi_clk phandle and the index to
refer and names need to be provided by the firmware.

--
Regards,
Sudeep