Re: [PATCH v2 02/16] dt-bindings: stm32: stm32mp25: add `access-controller-cell` property

[Gatien CHEVALLIER <gatien.chevallier@foss.st.com>]

Hello Rob,

On 7/15/25 05:17, Rob Herring wrote:
> On Fri, Jul 11, 2025 at 04:48:54PM +0200, Clément Le Goffic wrote:
>> RCC is able to check the availability of a clock.
>> Allow to query the RCC with a firewall ID.
> 
> If it is tied to a clock, do we need another provider? We have the
> "protected clocks" thing, but that might be a bit different.
> 

I couldn't find any reference to "protected-clocks" outside of qcom
related code, is there a documentation? (Couldn't find it in
clocks.yaml).

The RCC is firewall-aware and has it's own firewall configuration at
RCC level for some system resources. When checking access to a clock,
or a reset, we're reading RCC registers, hence declaring it as an
access-controller.

A RCC resource's firewall configuration usually covers more than a
clock.

>>
>> Signed-off-by: Clément Le Goffic <clement.legoffic@foss.st.com>
>> ---
>>   Documentation/devicetree/bindings/clock/st,stm32mp25-rcc.yaml | 7 +++++++
>>   1 file changed, 7 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/clock/st,stm32mp25-rcc.yaml b/Documentation/devicetree/bindings/clock/st,stm32mp25-rcc.yaml
>> index 88e52f10d1ec..4d471e3d89bc 100644
>> --- a/Documentation/devicetree/bindings/clock/st,stm32mp25-rcc.yaml
>> +++ b/Documentation/devicetree/bindings/clock/st,stm32mp25-rcc.yaml
>> @@ -31,6 +31,11 @@ properties:
>>     '#reset-cells':
>>       const: 1
>>   
>> +  '#access-controller-cells':
>> +    const: 1
>> +    description:
>> +      Contains the firewall ID associated to the peripheral.
>> +
>>     clocks:
>>       items:
>>         - description: CK_SCMI_HSE High Speed External oscillator (8 to 48 MHz)
>> @@ -123,6 +128,7 @@ required:
>>     - reg
>>     - '#clock-cells'
>>     - '#reset-cells'
>> +  - '#access-controller-cells'
>>     - clocks
>>   
>>   additionalProperties: false
>> @@ -136,6 +142,7 @@ examples:
>>           reg = <0x44200000 0x10000>;
>>           #clock-cells = <1>;
>>           #reset-cells = <1>;
>> +        #access-controller-cells = <1>;
>>           clocks =  <&scmi_clk CK_SCMI_HSE>,
>>                     <&scmi_clk CK_SCMI_HSI>,
>>                     <&scmi_clk CK_SCMI_MSI>,
>>
>> -- 
>> 2.43.0
>>

Best regards,
Gatien