linux-kernel - Re: [PATCH 03/21] dt-bindings: gpu: img: Power domain details

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Message-ID: <ff4e96e4-ebc2-4c50-9715-82ba3d7b8612@imgtec.com>
Date: Wed, 6 Nov 2024 10:18:01 +0000
From: Matt Coster <Matt.Coster@...tec.com>
To: Conor Dooley <conor@...nel.org>
CC: Frank Binns <Frank.Binns@...tec.com>, David Airlie <airlied@...il.com>,
        Simona Vetter <simona@...ll.ch>,
        Maarten Lankhorst
	<maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>, Nishanth Menon <nm@...com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Tero
 Kristo <kristo@...nel.org>,
        "dri-devel@...ts.freedesktop.org"
	<dri-devel@...ts.freedesktop.org>,
        "devicetree@...r.kernel.org"
	<devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>,
        Randolph Sapp <rs@...com>, Darren
 Etheridge <detheridge@...com>
Subject: Re: [PATCH 03/21] dt-bindings: gpu: img: Power domain details

On 05/11/2024 18:13, Conor Dooley wrote:
> On Tue, Nov 05, 2024 at 06:05:54PM +0000, Conor Dooley wrote:
>> On Tue, Nov 05, 2024 at 03:58:09PM +0000, Matt Coster wrote:
>>> The single existing GPU (AXE-1-16M) only requires a single power domain.
>>> Subsequent patches will add support for BXS-4-64 MC1, which has two power
>>> domains. Add infrastructure now to allow for this.
>>>
>>> Signed-off-by: Matt Coster <matt.coster@...tec.com>
>>> ---
>>>  .../devicetree/bindings/gpu/img,powervr-rogue.yaml | 29 +++++++++++++++++++++-
>>>  1 file changed, 28 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/Documentation/devicetree/bindings/gpu/img,powervr-rogue.yaml b/Documentation/devicetree/bindings/gpu/img,powervr-rogue.yaml
>>> index 6924831d3e9dd9b2b052ca8f9d7228ff25526532..55f422be1bc5b7564e3e81f24c4b93857f3e12fe 100644
>>> --- a/Documentation/devicetree/bindings/gpu/img,powervr-rogue.yaml
>>> +++ b/Documentation/devicetree/bindings/gpu/img,powervr-rogue.yaml
>>> @@ -49,7 +49,16 @@ properties:
>>>      maxItems: 1
>>>  
>>>    power-domains:
>>> -    maxItems: 1
>>> +    minItems: 1
>>> +    maxItems: 2
>>> +
>>> +  power-domain-names:
>>> +    oneOf:
>>> +      - items:
>>> +          - const: a
>>> +      - items:
>>> +          - const: a
>>> +          - const: b
> 
> Additionally, a & b? Are those actually the names for the power domains?

Sadly yes, Rogue has power domains that are literally just A, B, etc. I
wouldn't believe me either; the attached image is taken directly from
the documentation for BXS-4-64.

>>>  
>>>  required:
>>>    - compatible
>>> @@ -57,10 +66,27 @@ required:
>>>    - clocks
>>>    - clock-names
>>>    - interrupts
>>> +  - power-domains
>>> +  - power-domain-names
>>
>> A new required property is an ABI break. Please explain why this is
>> acceptable in your commit message.

Strictly it's only necessary for multi-domain GPUs, or perhaps in
instances where the SoC power controller already enforces the
dependencies between power domains. In reality, I think it was simply an
oversight not to enfore this requirement in the first place. We have
very, very few cores that require <2 power domains so names are always
required if domains are enumerated in dt.

Would you prefer we drop the requirement for "power-domains" and gate
the requirement for "power-domain-names" behind >2 domains, or just
explain the change properly and make the ABI break now while only one
core is supported?

Cheers,
Matt

>>>  additionalProperties: false
>>>  
>>>  allOf:
>>> +  # Cores with a single power domain
>>> +  - if:
>>> +      properties:
>>> +        compatible:
>>> +          contains:
>>> +            anyOf:
>>> +              - const: img,img-axe-1-16m
>>> +    then:
>>> +      properties:
>>> +        power-domains:
>>> +          minItems: 1
>>> +          maxItems: 1
>>> +        power-domain-names:
>>> +          items:
>>> +            - const: a
>>>    # Vendor integrations using a single clock domain
>>>    - if:
>>>        properties:
>>> @@ -90,4 +116,5 @@ examples:
>>>          clock-names = "core";
>>>          interrupts = <GIC_SPI 86 IRQ_TYPE_LEVEL_HIGH>;
>>>          power-domains = <&k3_pds 187 TI_SCI_PD_EXCLUSIVE>;
>>> +        power-domain-names = "a";
>>>      };
>>>
>>> -- 
>>> 2.47.0
>>>

-- 
Matt Coster
E: matt.coster@...tec.com
Download attachment "img-bxs-4-64-power-domains.png" of type "image/png" (25871 bytes)

Download attachment "OpenPGP_signature.asc" of type "application/pgp-signature" (237 bytes)