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

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Date:   Tue, 18 Jul 2023 11:32:16 +0000
From:   Frank Binns <Frank.Binns@...tec.com>
To:     "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "krzysztof.kozlowski@...aro.org" <krzysztof.kozlowski@...aro.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: Re: [PATCH v4 02/17] dt-bindings: gpu: Add Imagination
 Technologies PowerVR GPU

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.

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?

Thanks
Frank

> 
> 
> Best regards,
> Krzysztof
>