linux-kernel - Re: [PATCH v4 02/17] dt-bindings: gpu: Add Imagination Technologies PowerVR GPU

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Date:   Tue, 18 Jul 2023 15:06:03 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Frank Binns <Frank.Binns@...tec.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        Sarah Walker <Sarah.Walker@...tec.com>
Cc:     "luben.tuikov@....com" <luben.tuikov@....com>,
        "christian.koenig@....com" <christian.koenig@....com>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "tzimmermann@...e.de" <tzimmermann@...e.de>,
        "mripard@...nel.org" <mripard@...nel.org>,
        "matthew.brost@...el.com" <matthew.brost@...el.com>,
        "daniel@...ll.ch" <daniel@...ll.ch>,
        "hns@...delico.com" <hns@...delico.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "boris.brezillon@...labora.com" <boris.brezillon@...labora.com>,
        "dakr@...hat.com" <dakr@...hat.com>,
        "maarten.lankhorst@...ux.intel.com" 
        <maarten.lankhorst@...ux.intel.com>, "afd@...com" <afd@...com>,
        "conor+dt@...nel.org" <conor+dt@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "airlied@...il.com" <airlied@...il.com>,
        Donald Robson <Donald.Robson@...tec.com>,
        "faith.ekstrand@...labora.com" <faith.ekstrand@...labora.com>
Subject: Re: [PATCH v4 02/17] dt-bindings: gpu: Add Imagination Technologies
 PowerVR GPU

On 18/07/2023 13:32, Frank Binns wrote:
> Hi Krzysztof,
> 
> On Mon, 2023-07-17 at 09:29 +0200, Krzysztof Kozlowski wrote:
>> On 14/07/2023 16:25, Sarah Walker wrote:
>>> Add the device tree binding documentation for the Series AXE GPU used in
>>> TI AM62 SoCs.
>>>
>>
>> ...
>>
>>> +
>>> +  clocks:
>>> +    minItems: 1
>>> +    maxItems: 3
>>> +
>>> +  clock-names:
>>> +    items:
>>> +      - const: core
>>> +      - const: mem
>>> +      - const: sys
>>> +    minItems: 1
>>
>> Why clocks for this device vary? That's really unusual to have a SoC IP
>> block which can have a clock physically disconnected, depending on the
>> board (not SoC!).
> 
> By default, this GPU IP (Series AXE) operates on a single clock (the core
> clock), but the SoC vendor can choose at IP integration time to run the memory
> and SoC interfaces on separate clocks (mem and sys clocks respectively). We also
> have IP, such as the Series 6XT, that requires all 3 clocks.

Currently you have only one SoC vendor with only one SoC, so the clocks
do not vary. Describing the clocks for all possible variants is a good
idea, but then this should be clear that this implementation uses subset.

> 
> So the situation here is that Series AXE may have 1 or 3 clocks, but the TI
> implementation being added only has 1.
> 
> I guess we need to add something like:
> 
>   allOf:
>     - if:
>         properties:
>           compatible:
>             contains:
>               const: ti,am62-gpu
>       then:
>         properties:
>           clocks:
>             maxItems: 1
> 
> Or should we be doing something else?

Yes. clock-names as well..


Best regards,
Krzysztof