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 11:51:59 -0500
From:   Jassi Brar <jassisinghbrar@...il.com>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     Peng Fan <peng.fan@....com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....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 4:32 AM Sudeep Holla <sudeep.holla@....com> wrote:
>
> On Fri, Aug 30, 2019 at 02:52:40AM -0500, Jassi Brar wrote:
> > On Fri, Aug 30, 2019 at 2:37 AM Peng Fan <peng.fan@....com> wrote:
>
> [...]
>
> > >
> > > 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 ?
> >
>
> I might have missed to follow this, but what's the advantage of doing so ?
> Which can't single controller instance deal with all the channels ?
>
There are many advantages ...
1) Design reflects the reality - two smc/hvc instructions have nothing
tying them together.
2) Driver code becomes simpler - don't have to pre-populate channels,
deducting from the size of func-ids array.
3) Driver becomes more flexible - We can have channels that pass
func-id runtime and channels that pass via DT (if we must have the
option of DT property).

-jassi