linux-kernel - Re: [PATCH v6 00/12] ARM/MIPS: DTS: add child nodes describing the PVRSGX GPU present in some OMAP SoC and JZ4780 (and many more)

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Date:   Wed, 22 Apr 2020 18:09:01 +0200
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Maxime Ripard <maxime@...no.tech>
Cc:     Tony Lindgren <tony@...mide.com>,
        Philipp Rossak <embed3d@...il.com>,
        Jonathan Bakker <xc-racer2@...e.ca>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Benoît Cousson <bcousson@...libre.com>,
        Paul Cercueil <paul@...pouillou.net>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paulburton@...nel.org>,
        James Hogan <jhogan@...nel.org>, Kukjin Kim <kgene@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        "open list:DRM PANEL DRIVERS" <dri-devel@...ts.freedesktop.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-omap <linux-omap@...r.kernel.org>,
        OpenPVRSGX Linux Driver Group <openpvrsgx-devgroup@...ux.org>,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>, kernel@...a-handheld.com,
        linux-mips@...r.kernel.org,
        arm-soc <linux-arm-kernel@...ts.infradead.org>,
        linux-samsung-soc@...r.kernel.org
Subject: Re: [PATCH v6 00/12] ARM/MIPS: DTS: add child nodes describing the PVRSGX GPU present in some OMAP SoC and JZ4780 (and many more)

Hi Maxime,

> Am 22.04.2020 um 17:13 schrieb Maxime Ripard <maxime@...no.tech>:
> 
> On Wed, Apr 22, 2020 at 09:10:57AM +0200, H. Nikolaus Schaller wrote:
>>> Am 22.04.2020 um 08:58 schrieb Maxime Ripard <maxime@...no.tech>:
>>>> 
>>>> It also allows to handle different number of clocks (A31 seems to
>>>> need 4, Samsung, A83 and JZ4780 one) without changing the sgx bindings
>>>> or making big lists of conditionals. This variance would be handled
>>>> outside the sgx core bindings and driver.
>>> 
>>> I disagree. Every other GPU binding and driver is handling that just fine, and
>>> the SGX is not special in any case here.
>> 
>> Can you please better explain this? With example or a description
>> or a proposal?
> 
> I can't, I don't have any knowledge about this GPU.

Hm. Now I am fully puzzled.
You have no knowledge about this GPU but disagree with our proposal?
Is it just gut feeling?

Anyways, we need to find a solution. Together.

> 
>> I simply do not have your experience with "every other GPU" as you have.
>> And I admit that I can't read from your statement what we should do
>> to bring this topic forward.
>> 
>> So please make a proposal how it should be in your view.
> 
> If you need some inspiration, I guess you could look at the mali and vivante
> bindings once you have an idea of what the GPU needs across the SoCs it's
> integrated in.

Well, I do not need inspiration, we need to come to an agreement about
img,pvrsgx.yaml and we need some maintainer to finally pick it up.

I wonder how we can come to this stage.

If I look at vivante,gc.yaml or arm,mali-utgard.yaml I don't
see big differences to what we propose and those I see seem to come
from technical differences between sgx, vivante, mali etc. So there
is no single scheme that fits all different gpu types.

One thing we can learn is that "core" seems to be a de facto standard 
for the core clock-name. An alternative "gpu" is used by nvidia,gk20a.txt.

BR and thanks,
Nikolaus