Date: Tue, 3 Oct 2023 09:45:36 +0200
From: Gatien CHEVALLIER <gatien.chevallier@...s.st.com>
To: Rob Herring <robh@...nel.org>
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Subject: Re: [PATCH v5 01/11] dt-bindings: document generic access controller

Hi Rob,

On 10/2/23 19:30, Rob Herring wrote:
> On Fri, Sep 29, 2023 at 04:28:42PM +0200, Gatien Chevallier wrote:
>> From: Oleksii Moisieiev <Oleksii_Moisieiev@...m.com>
>>
>> Introducing of the generic access controller bindings for the
>> access controller provider and consumer devices. Those bindings are
>> intended to allow a better handling of accesses to resources in a
>> hardware architecture supporting several compartments.
>>
>> This patch is based on [1]. It is integrated in this patchset as it
>> provides a use-case for it.
>>
>> Diffs with [1]:
>> 	- Rename feature-domain* properties to access-control* to narrow
>> 	  down the scope of the binding
>> 	- YAML errors and typos corrected.
>> 	- Example updated
>> 	- Some rephrasing in the binding description
>>
>> [1]: https://lore.kernel.org/lkml/0c0a82bb-18ae-d057-562b
>>
>> Signed-off-by: Oleksii Moisieiev <oleksii_moisieiev@...m.com>
>> Signed-off-by: Gatien Chevallier <gatien.chevallier@...s.st.com>
>>
>> ---
>> Changes in V5:
>> 	- Diffs with [1]
>> 	- Discarded the [IGNORE] tag as the patch is now part of the
>> 	  patchset
>>
>>   .../access-controllers/access-controller.yaml | 90 +++++++++++++++++++
>>   1 file changed, 90 insertions(+)
>>   create mode 100644 Documentation/devicetree/bindings/access-controllers/access-controller.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/access-controllers/access-controller.yaml b/Documentation/devicetree/bindings/access-controllers/access-controller.yaml
>> new file mode 100644
>> index 000000000000..9d305fccc333
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/access-controllers/access-controller.yaml
>> @@ -0,0 +1,90 @@
>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/access-controllers/access-controller.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: Generic Domain Access Controller
>> +
>> +maintainers:
>> +  - Oleksii Moisieiev <oleksii_moisieiev@...m.com>
>> +
>> +description: |+
>> +  Common access controllers properties
>> +
>> +  Access controllers are in charge of stating which of the hardware blocks under
>> +  their responsibility (their domain) can be accesssed by which compartment. A
>> +  compartment can be a cluster of CPUs (or coprocessors), a range of addresses
>> +  or a group of hardware blocks. An access controller's domain is the set of
>> +  resources covered by the access controller.
>> +
>> +  This device tree bindings can be used to bind devices to their access
>> +  controller provided by access-controller property. In this case, the device is
>> +  a consumer and the access controller is the provider.
>> +
>> +  An access controller can be represented by any node in the device tree and
>> +  can provide one or more configuration parameters, needed to control parameters
>> +  of the consumer device. A consumer node can refer to the provider by phandle
>> +  and a set of phandle arguments, specified by '#access-controller-cells'
>> +  property in the access controller node.
>> +
>> +  Access controllers are typically used to set/read the permissions of a
>> +  hardware block and grant access to it. Any of which depends on the access
>> +  controller. The capabilities of each access controller are defined by the
>> +  binding of the access controller device.
>> +
>> +  Each node can be a consumer for the several access controllers.
>> +
>> +# always select the core schema
>> +select: true
>> +
>> +properties:
>> +  "#access-controller-cells":
>> +    $ref: /schemas/types.yaml#/definitions/uint32
> 
> Drop. "#.*-cells" already defines the type.
> 

Ok, I will drop it for V6

>> +    description:
>> +      Number of cells in a access-controller specifier;
>> +      Can be any value as specified by device tree binding documentation
>> +      of a particular provider.
>> +
>> +  access-control-provider:
>> +    description:
>> +      Indicates that the node is an access controller.
> 
> Drop. The presence of "#access-controller-cells" is enough to do that.
> 

Ok, I wasn't sure. I'll will drop it for V6

>> +
>> +  access-controller-names:
>> +    $ref: /schemas/types.yaml#/definitions/string-array
>> +    description:
>> +      A list of access-controller names, sorted in the same order as
>> +      access-controller entries. Consumer drivers will use
>> +      access-controller-names to match with existing access-controller entries.
>> +
>> +  access-controller:
> 
> For consistency with other provider bindings: access-controllers
> 

Ack

>> +    $ref: /schemas/types.yaml#/definitions/phandle-array
>> +    description:
>> +      A list of access controller specifiers, as defined by the
>> +      bindings of the access-controller provider.
>> +
>> +additionalProperties: true
>> +
>> +examples:
>> +  - |
>> +    uart_controller: access-controller@...00 {
>> +        reg = <0x50000 0x10>;
>> +        access-control-provider;
>> +        #access-controller-cells = <2>;
>> +    };
>> +
>> +    bus_controller: bus@...00 {
>> +        reg = <0x60000 0x10000>;
>> +        #address-cells = <1>;
>> +        #size-cells = <1>;
>> +        ranges;
>> +        access-control-provider;
>> +        #access-controller-cells = <3>;
>> +
>> +        uart4: serial@...00 {
>> +            reg = <0x60100 0x400>;
>> +            access-controller = <&uart_controller 1 2>,
>> +                                <&bus_controller 1 3 5>;
>> +            access-controller-names = "controller", "bus-controller";
> 
> Not great names. It should indicate what access is being controlled
> locally. Perhaps "reg" for register access, "dma" or "bus" for bus
> master access. (Not sure what your uart_controller is controlling access
> to.)
> 
> Rob

Yes, I agree it's poor naming. I'll come up with something more
adequate. Thank you for the input.

Best regards,
Gatien

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