Re: [PATCH 2/3] media: iris: Skip SCM call for non-SCM PAS backend

[Sumit Garg]

Hey Vikash,

On Thu, Sep 17, 2026 at 5:11 PM Vikash Garodia
<vikash.garodia@xxxxxxxxxxxxxxxx> wrote:
>
> Hi Sumit,
>
> On 9/14/2026 11:44 AM, Sumit Garg wrote:
> > Hey Konrad,
> >
> > On Fri, Sep 11, 2026 at 7:54 PM Konrad Dybcio
> > <konrad.dybcio@xxxxxxxxxxxxxxxx> wrote:
> >>
> >> On 9/11/26 2:38 PM, Sumit Garg wrote:
> >>> From: Jorge Ramirez-Ortiz <jorge.ramirez@xxxxxxxxxxxxxxxx>
> >>>
> >>> qcom_scm_mem_protect_video_var() is only serviced by the SCM backend;
> >>> with OP-TEE the TEE owns secure memory protection. Use
> >>> qcom_pas_get_backend() to issue the SCM call only for the SCM backend.
> >>>
> >>> Assisted-by: Copilot:claude-opus-4.8
> >>> Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez.ortiz@xxxxxxxxx>
> >>> Co-developed-by: Sumit Garg <sumit.garg@xxxxxxxxxxxxxxxx>
> >>> Signed-off-by: Sumit Garg <sumit.garg@xxxxxxxxxxxxxxxx>
> >>> ---
> >>
> >> [...]
> >>
> >>> +     /*
> >>> +      * qcom_scm_mem_protect_video_var() only applies to the SCM backend;
> >>> +      * other backends (e.g. OP-TEE) own secure memory protection and do
> >>> +      * not service this call.
> >>
> >> Can you not just stub it out in TF-A then?
> >>
> >
> > Please don't, we don't want to support these random SCM calls ABI per
> > subsystem with the open boot stack. All the config in this case for
> > video is handled by OP-TEE itself.
>
> Could you please help me understand the demerit in stubbing it out and
> let that be a dummy ABI in OPTEE world ? that way client driver can
> remain agnostic of the calls being routed to OPTEE or QTEE
>

The main disadvantage is that we don't want to carry these custom SCM
ABIs per kernel subsystem with the open source TF-A/OP-TEE boot stack.
ABIs always come with maintenance burdens, especially the custom ones
we have in this case.

Since we started from scratch for the open source boot stack, the
motivation is to keep the TZ ABI minimal and that too with
discoverable OP-TEE services like the PAS service.

-Sumit