linux-kernel - Re: [PATCH v5 1/2] dt-bindings: mailbox: add binding doc for the ARM SMC/HVC mailbox

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Date:   Fri, 30 Aug 2019 02:52:40 -0500
From:   Jassi Brar <jassisinghbrar@...il.com>
To:     Peng Fan <peng.fan@....com>
Cc:     "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "sudeep.holla@....com" <sudeep.holla@....com>,
        "andre.przywara@....com" <andre.przywara@....com>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH v5 1/2] dt-bindings: mailbox: add binding doc for the ARM
 SMC/HVC mailbox

On Fri, Aug 30, 2019 at 2:37 AM Peng Fan <peng.fan@....com> wrote:
>
> Hi Jassi,
>
> > Subject: Re: [PATCH v5 1/2] dt-bindings: mailbox: add binding doc for the ARM
> > SMC/HVC mailbox
> >
> > On Fri, Aug 30, 2019 at 1:28 AM Peng Fan <peng.fan@....com> wrote:
> >
> > > > > +examples:
> > > > > +  - |
> > > > > +    sram@...000 {
> > > > > +      compatible = "mmio-sram";
> > > > > +      reg = <0x0 0x93f000 0x0 0x1000>;
> > > > > +      #address-cells = <1>;
> > > > > +      #size-cells = <1>;
> > > > > +      ranges = <0 0x0 0x93f000 0x1000>;
> > > > > +
> > > > > +      cpu_scp_lpri: scp-shmem@0 {
> > > > > +        compatible = "arm,scmi-shmem";
> > > > > +        reg = <0x0 0x200>;
> > > > > +      };
> > > > > +
> > > > > +      cpu_scp_hpri: scp-shmem@200 {
> > > > > +        compatible = "arm,scmi-shmem";
> > > > > +        reg = <0x200 0x200>;
> > > > > +      };
> > > > > +    };
> > > > > +
> > > > > +    firmware {
> > > > > +      smc_mbox: mailbox {
> > > > > +        #mbox-cells = <1>;
> > > > > +        compatible = "arm,smc-mbox";
> > > > > +        method = "smc";
> > > > > +        arm,num-chans = <0x2>;
> > > > > +        transports = "mem";
> > > > > +        /* Optional */
> > > > > +        arm,func-ids = <0xc20000fe>, <0xc20000ff>;
> > > > >
> > > > SMC/HVC is synchronously(block) running in "secure mode", i.e, there
> > > > can only be one instance running platform wide. Right?
> > >
> > > I think there could be channel for TEE, and channel for Linux.
> > > For virtualization case, there could be dedicated channel for each VM.
> > >
> > I am talking from Linux pov. Functions 0xfe and 0xff above, can't both be
> > active at the same time, right?
>
> If I get your point correctly,
> On UP, both could not be active. On SMP, tx/rx could be both active, anyway
> this depends on secure firmware and Linux firmware design.
>
> Do you have any suggestions about arm,func-ids here?
>
I was thinking if this is just an instruction, why can't each channel
be represented as a controller, i.e, have exactly one func-id per
controller node. Define as many controllers as you need channels ?

-j