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SubjectRe: [PATCH v2 2/2] firmware: arm_scmi: Augment SMC/HVC to allow optional interrupt
On Fri, Nov 13, 2020 at 9:36 AM Sudeep Holla <sudeep.holla@arm.com> wrote:
>
> 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@arm.com> 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 ?

Hi Sudeep,
I have an answer for this but allow me time to contact the platform FW
engineer to make sure I have the full picture -- this may take a day
or two. Regardless, our implementation has already "shipped" to
customers for some time so we may not be able to change it.
Regards, Jim
>
>
> --
> Regards,
> Sudeep
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