Re: [PATCH 2/6] dt-bindings: arm: keystone: ti,sci: Add ti,tda54-sci-pdm compatible

[Padhi, Beleswar]

On 10/2/2026 12:01 PM, Krzysztof Kozlowski wrote:
> On Thu, Oct 01, 2026 at 01:11:27AM +0530, Beleswar Padhi wrote:
> > The previous TI K2G and K3 architectures were tightly coupled systems in
> > terms of Safety and Security. All the TI-SCI messages from HLOS (Linux)
> > were sent to a single sec proxy thread terminating at the core running
> > Safety service (DM). In K2G systems, DM handled both Safety & Security
> > requests by itself. Whereas in K3 systems, DM serviced the Safety
> > requests itself, and forwarded the Security requests to core running
> > Security service (TIFS) on the HLOS's behalf. This posed various
> > limitations:
> >     a. Increased latency: An extra forwarding hop through DM adds latency
> >        in requests and responses.
> >     b. Freedom From Interference (FFI) concerns: Having Safety service
> >        proxy Security's requests (& vice versa) undermines the isolation
> >        and FFI of the system.
> >     c. Potential Deadlock Scenario: Forwarding messages between Safety
> >        and Security cores can result in a deadlock if there are circular
> >        dependencies.
> >
> > To eliminate all the above limitations, the TI TDA54 class of SoCs
> > introduce an architectural change: Isolation of Security and Safety
> > services. To realize this enhanced isolation in hardware, two
> > independent sec proxy threads are now provided for HLOS to communicate
> > separately with the Security and Safety cores respectively. And the
> > TI-SCI message forwarding has been eliminated in Software. The System
> > Firmware ABI5.0 version necessitates this improved isolation and FFI
> > change.
> I don't get at all how above description helps to understand this patch
> and this new compatible, except that this is not compatible with old
> variants.


You just answered your own question.

>   So 30 lines of text instead of 3?


The existing system controllers have been compatible in all TI SoCs
for over 10+ years since Keystone generations. Using 30 lines of
text to explain "why" the new system controller is not compatible
with old variants is worth it.

> > Add the compatible string for TI TDA54 SoC PDM system controller to
> > support ABI5.0 communication protocol.
> >
> > Signed-off-by: Beleswar Padhi <b-padhi@xxxxxx>
> > ---
> > Note: This patch is independent and can be applied directly.
> >
> > Cc: Nishanth Menon <nm@xxxxxx>
> > Cc: Tero Kristo <kristo@xxxxxxxxxx>
> > Cc: Santosh Shilimkar <ssantosh@xxxxxxxxxx>
> > Cc: Rob Herring <robh@xxxxxxxxxx>
> > Cc: Krzysztof Kozlowski <krzk+dt@xxxxxxxxxx>
> > Cc: Conor Dooley <conor+dt@xxxxxxxxxx>
> > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> > Cc: devicetree@xxxxxxxxxxxxxxx
> > Cc: linux-kernel@xxxxxxxxxxxxxxx
> >
> >   .../bindings/arm/keystone/ti,sci.yaml         | 33 +++++++++++++++++++
> >   1 file changed, 33 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/arm/keystone/ti,sci.yaml b/Documentation/devicetree/bindings/arm/keystone/ti,sci.yaml
> > index 67acce8a559a1..f0548382f7d52 100644
> > --- a/Documentation/devicetree/bindings/arm/keystone/ti,sci.yaml
> > +++ b/Documentation/devicetree/bindings/arm/keystone/ti,sci.yaml
> > @@ -20,6 +20,11 @@ description: |
> >     initialized early into boot process and provides services to Operating Systems
> >     on multiple processors including ones running Linux.
> >   
> > +  The TI TDA54 SoC, however, has two independent system controller instances - a
> > +  PDM (Power and Device Management) system controller, which handles Power,
> > +  Device, Clock, and Reset Management, and a separate SMS (Security Management
> > +  Subsystem) system controller, which handles security services.
> > +
> >     See https://software-dl.ti.com/tisci/esd/latest/index.html for protocol definition.
> >   
> >     The TI-SCI node describes the Texas Instrument's System Controller entity node.
> > @@ -40,6 +45,10 @@ properties:
> >         - description: System controller on TI AM654 SoC
> >           items:
> >             - const: ti,am654-sci
> > +      - description: |
> > +          System controller for Power and Device Management on TI TDA54 SoC
> That's redundant, you just repeated the compatible.


I did not. The compatible says "pdm". Not everyone understands the
acronym.

> > +        items:
> > +          - const: ti,tda54-sci-pdm
> Why it cannot be enum with existing entry(ies)?


It should be. Will address this in revision.

> >   
> >     reg-names:
> >       description: |
> > @@ -135,3 +144,27 @@ examples:
> >           #reset-cells = <2>;
> >         };
> >       };
> > +
> > +  - |
> > +    pdm: system-controller {
> No need for new example which is the same.


Okay, will drop in revision.

Thanks,
Beleswar

> Best regards,
> Krzysztof