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Subject: Re: [PATCH RFC 01/10] dt-bindings: gpu: Add PowerVR Series5 SGX GPUs
From:   "H. Nikolaus Schaller" <hns@goldelico.com>
In-Reply-To: <6gpehpoz54f5lxhmvirqbfwmq7dpgiroy27cljpvu66wtn7aqy@lgrh7wysyxnp>
Date:   Thu, 7 Dec 2023 11:33:53 +0100
Cc:     Andrew Davis <afd@ti.com>, Frank Binns <frank.binns@imgtec.com>,
        Donald Robson <donald.robson@imgtec.com>,
        Matt Coster <matt.coster@imgtec.com>,
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        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Chen-Yu Tsai <wens@csie.org>,
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To:     Maxime Ripard <mripard@kernel.org>
Precedence: bulk

Hi Maxime,

> Am 07.12.2023 um 10:20 schrieb Maxime Ripard <mripard@kernel.org>:
>=20
> On Tue, Dec 05, 2023 at 02:50:08PM +0100, H. Nikolaus Schaller wrote:
>> Hi,
>>=20
>>> Am 05.12.2023 um 14:29 schrieb Maxime Ripard <mripard@kernel.org>:
>>>=20
>>> Hi,
>>>=20
>>> On Tue, Dec 05, 2023 at 09:18:58AM +0100, H. Nikolaus Schaller =
wrote:
>>>>> Am 05.12.2023 um 07:57 schrieb Maxime Ripard <mripard@kernel.org>:
>>>>>=20
>>>>> On Mon, Dec 04, 2023 at 12:22:36PM -0600, Andrew Davis wrote:
>>>>>> The Imagination PowerVR Series5 "SGX" GPU is part of several SoCs =
from
>>>>>> multiple vendors. Describe how the SGX GPU is integrated in these =
SoC,
>>>>>> including register space and interrupts. Clocks, reset, and power =
domain
>>>>>> information is SoC specific.
>>>>>>=20
>>>>>> Signed-off-by: Andrew Davis <afd@ti.com>
>>>>>> ---
>>>>>> .../devicetree/bindings/gpu/img,powervr.yaml  | 69 =
+++++++++++++++++--
>>>>>> 1 file changed, 63 insertions(+), 6 deletions(-)
>>>>>=20
>>>>> I think it would be best to have a separate file for this, =
img,sgx.yaml
>>>>> maybe?
>>>>=20
>>>> Why?
>>>=20
>>> Because it's more convenient?
>>=20
>> Is it?
>=20
> It's for a separate architecture, with a separate driver, maintained =
out
> of tree by a separate community, with a separate set of requirements =
as
> evidenced by the other thread. And that's all fine in itself, but
> there's very little reason to put these two bindings in the same file.
>=20
> We could also turn this around, why is it important that it's in the
> same file?

Same vendor. And enough similarity in architectures, even a logical =
sequence
of development of versions (SGX =3D Version 5, Rogue =3D Version 6+) =
behind.
(SGX and Rogue seem to be just trade names for their architecture =
development).

AFAIK bindings should describe hardware and not communities or drivers
or who is currently maintaining it. The latter can change, the first =
not.

>=20
>>>> The whole family of IMG GPUs is PowerVR and SGX and Rogue are =
generations 5 and 6++:
>>>>=20
>>>> https://en.wikipedia.org/wiki/PowerVR
>>>=20
>>> That's not really relevant as far as bindings go.
>>=20
>> But maybe for choosing binding file names. Well they are machine =
readable
>> but sometimes humans work with them.
>=20
> Heh. It's something that can also be easily grepped,

Yes, arbitrarily introduced confusion can always be resolved by search =
engines
and makes them necessary and more and more advanced :)

> and the name is
> never going to reflect all the compatibles in a binding so it's what
> you'll end up doing anyway. But feel free to suggest another name to
> avoid the confusion.

Well,

1. rename img,powervr.yaml =3D> img,powervr-rogue.yaml
2. new file img,powervr-sgx.yaml

to have at least a systematic approach here.

>>> We have multiple
>>> binding files for devices of the same generation, or single bindings
>>> covering multiple generations.
>>>=20
>>> The important part is that every compatible is documented. It =
doesn't
>>> really matter how or where.
>>=20
>> Yes, and that is why I would find it more convenient to have a single
>> "img,powervr.yaml" for all variations unless it becomes filled with
>> unrelated stuff (which isn't as far as I see).
>=20
> Again, hard disagree there.

I am fine with that. I just advocate to follow the KISS principle.

Same vendor, similar purpose, similar architecture =3D> single bindings =
file
as Andrew proposed.

BR,
Nikolaus=