Re: [PATCH v2 2/2] firmware: arm_scmi: Augment SMC/HVC to allow optional interrupt

From: Sudeep Holla
Date: Fri Nov 13 2020 - 09:36:34 EST


On Fri, Nov 13, 2020 at 09:26:43AM -0500, Jim Quinlan wrote:
> Hi, these are fast calls. Regards, Jim
>
>
> On Fri, Nov 13, 2020 at 4:47 AM Sudeep Holla <sudeep.holla@xxxxxxx> wrote:
> >
> > On Thu, Nov 12, 2020 at 12:56:27PM -0500, Jim Quinlan wrote:
> > > The SMC/HVC SCMI transport is modified to allow the completion of an SCMI
> > > message to be indicated by an interrupt rather than the return of the smc
> > > call. This accommodates the existing behavior of the BrcmSTB SCMI
> > > "platform" whose SW is already out in the field and cannot be changed.
> > >
> >
> > Sorry for missing to check with you earlier. Are these not fast smc calls ?
> > Can we check the SMC Function IDs for the same and expect IRQ to be present
> > if they are not fast calls ?
> Hi, if I understand you correctly you want to do something like this:
>
> if (! ARM_SMCCC_IS_FAST_CALL(func_id)) {
> /* look for irq and request it */
> }
>

Yes.

> But we do use fast calls.

What was the rationale for retaining fast SMC calls but use IRQ for Tx
completion ?

Is it because you offload it to some other microprocessor and don't
continue execution on secure side in whcih case you can afford fast call ?

--
Regards,
Sudeep