On Thu, Nov 5, 2020 at 10:13 AM Rob Herring <robh@xxxxxxxxxx> wrote:
>
> On Wed, Nov 4, 2020 at 4:04 PM Jim Quinlan <james.quinlan@xxxxxxxxxxxx> wrote:
> >
> > On Wed, Nov 4, 2020 at 4:50 PM Rob Herring <robh@xxxxxxxxxx> wrote:
> > >
> > > On Thu, Oct 29, 2020 at 03:59:06PM -0400, Jim Quinlan wrote:
> > > > Bindings are added. Only one interrupt is needed because
> > > > we do not yet employ the SCMI p2a channel.
> > >
> > > I still don't understand what this is. To repeat from v1: I thought SCMI
> > > was a mailbox consumer, not provider?
> >
> > Hi Rob,
> >
> > I'm not sure where I am implying that SCMI is a mailbox provider?
> > Should I not mention "SCMI" in the subject line?
> >
> > This is just a mailbox driver, "consumed" by SCMI. Our SCMI DT node
> > looks like this:
> >
> > brcm_scmi_mailbox: brcm_scmi_mailbox@0 {
> > #mbox-cells = <1>;
> > compatible = "brcm,brcmstb-mbox";
> > };
> >
> > brcm_scmi@0 {
> > compatible = "arm,scmi";
> > mboxes = <&brcm_scmi_mailbox 0>;;
> > mbox-names = "tx";
> > shmem = <&NWMBOX>;
> > /* ... */
> > };
>
> Okay, that makes more sense. Though it seems like this is just adding
> a pointless level of indirection to turn an interrupt into a mailbox.
> There's nothing more to 'the mailbox' is there?
Correct. Although you can see that it uses both interrupts and SMC
calls to get the job done.
> So why not either
> allow SCMI to have an interrupt directly
Not sure here -- perhaps the SCMI folks have an answer?
> or have a generic irq mailbox
> driver?
The SCMI implementation doesn't offer a generic irq mailbox driver
AFAICT. The SCMI folks recently provided an "smc transport" driver
in "drivers/firmware/arm_scmi/smc.c" -- it is close to what we need
but is missing interrupts.
Regards,
Jim Quinlan
Broadcom STB
>
> Rob
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