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

["Padhi, Beleswar" <b-padhi@ti.com>]

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@ti.com>
>> ---
>> Note: This patch is independent and can be applied directly.
>>
>> Cc: Nishanth Menon <nm@ti.com>
>> Cc: Tero Kristo <kristo@kernel.org>
>> Cc: Santosh Shilimkar <ssantosh@kernel.org>
>> Cc: Rob Herring <robh@kernel.org>
>> Cc: Krzysztof Kozlowski <krzk+dt@kernel.org>
>> Cc: Conor Dooley <conor+dt@kernel.org>
>> Cc: linux-arm-kernel@lists.infradead.org
>> Cc: devicetree@vger.kernel.org
>> Cc: linux-kernel@vger.kernel.org
>>
>>   .../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