RE: [PATCH v5 1/4] dt-bindings: firmware: Add bindings for ZynqMP firmware

[Jolly Shah]

> -----Original Message-----
> From: Sudeep Holla [mailto:sudeep.holla@xxxxxxx]
> Sent: Tuesday, March 13, 2018 3:16 AM
> To: Jolly Shah <JOLLYS@xxxxxxxxxx>
> Cc: Sudeep Holla <sudeep.holla@xxxxxxx>; gregkh@xxxxxxxxxxxxxxxxxxx;
> matt@xxxxxxxxxxxxxxxxxxx; hkallweit1@xxxxxxxxx; michal.simek@xxxxxxxxxx;
> robh+dt@xxxxxxxxxx; mark.rutland@xxxxxxx; ard.biesheuvel@xxxxxxxxxx;
> mingo@xxxxxxxxxx; keescook@xxxxxxxxxxxx; dmitry.torokhov@xxxxxxxxx;
> Rajan Vaja <RAJANV@xxxxxxxxxx>; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH v5 1/4] dt-bindings: firmware: Add bindings for ZynqMP
> firmware
> 
> 
> 
> On 12/03/18 23:07, Jolly Shah wrote:
> > Hi Sudeep,
> 
> >>>> Do you foresee using SMC/HVC for this firmware even on future
> platforms?
> >>>> If not, I suggest to keep the protocol part separate from the transport i.e.
> >>>> smc/hvc via ATF. It could be replaced with mailbox or some h/w
> >>>> mechanism in future ?
> >>>>
> >>>
> >>> We have PSCI and EEMI interfaces exposed to linux from ATF. PSCI is
> >>> an EEMI client. We do not have current plans to switch to mailbox as
> >>> it will require 2 communication channels to PMU as PSCI is through ATF.
> >>>
> >>
> >> OK, but I just saw some bindings that has mailbox interface, honestly
> >> it's getting too confusing with multiple series on the same thing
> >> floating and hence I requested to put it together as one series.
> >
> > Mailbox binding is used for power management driver. Mailbox is only
> > used for PMU->APU communication. APU->PMU communication is always
> > through EEMI firmware interface which is using SMC/HVC.
> >
> 
> Ah OK, is it because there's no non-secure mailbox or to avoid races, all non-
> secure EEMI is channeled through SMC ?
> 

2 reasons:
1> Avoid multiple EEMI communication channels as PSCI is through ATF.
2> We have some secure operations handled in ATF because of memory constraints on PMU

> --
> Regards,
> Sudeep