linux-kernel - Re: [PATCH v2 2/8] dt-bindings: display: add verisilicon,dc

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Message-ID: <CAH9NwWdx-Ut35RvhmNsdQbC4vfm3rH1VPN7H2uDBRsmsFjZU_Q@mail.gmail.com>
Date: Wed, 24 Sep 2025 20:15:46 +0200
From: Christian Gmeiner <christian.gmeiner@...il.com>
To: Icenowy Zheng <uwu@...nowy.me>
Cc: Rob Herring <robh@...nel.org>, Lucas Stach <l.stach@...gutronix.de>, 
	Russell King <linux+etnaviv@...linux.org.uk>, 
	moderated for non-subscribers <etnaviv@...ts.freedesktop.org>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Drew Fustini <fustini@...nel.org>, Guo Ren <guoren@...nel.org>, Fu Wei <wefu@...hat.com>, 
	Philipp Zabel <p.zabel@...gutronix.de>, Heiko Stuebner <heiko@...ech.de>, 
	Andrzej Hajda <andrzej.hajda@...el.com>, Neil Armstrong <neil.armstrong@...aro.org>, 
	Robert Foss <rfoss@...nel.org>, Laurent Pinchart <Laurent.pinchart@...asonboard.com>, 
	Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>, 
	Michal Wilczynski <m.wilczynski@...sung.com>, Han Gao <rabenda.cn@...il.com>, 
	Yao Zi <ziyao@...root.org>, dri-devel@...ts.freedesktop.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v2 2/8] dt-bindings: display: add verisilicon,dc

> > > > Verisilicon has a series of display controllers prefixed with DC
> > > > and
> > > > with self-identification facility like their GC series GPUs.
> > > >
> > > > Add a device tree binding for it.
> > > >
> > > > Depends on the specific DC model, it can have either one or two
> > > > display
> > > > outputs, and each display output could be set to DPI signal or
> > > > "DP"
> > > > signal (which seems to be some plain parallel bus to HDMI
> > > > controllers).
> > > >
> > > > Signed-off-by: Icenowy Zheng <uwu@...nowy.me>
> > > > ---
> > > > Changes in v2:
> > > > - Fixed misspelt "versilicon" in title.
> > > > - Moved minItems in clock properties to be earlier than items.
> > > > - Re-aligned multi-line clocks and resets in example.
> > > >
> > > >  .../bindings/display/verisilicon,dc.yaml      | 127
> > > > ++++++++++++++++++
> > > >  1 file changed, 127 insertions(+)
> > > >  create mode 100644
> > > > Documentation/devicetree/bindings/display/verisilicon,dc.yaml
> > > >
> > > > diff --git
> > > > a/Documentation/devicetree/bindings/display/verisilicon,dc.yaml
> > > > b/Documentation/devicetree/bindings/display/verisilicon,dc.yaml
> > > > new file mode 100644
> > > > index 0000000000000..07fedc4c7cc13
> > > > --- /dev/null
> > > > +++
> > > > b/Documentation/devicetree/bindings/display/verisilicon,dc.yaml
> > > > @@ -0,0 +1,127 @@
> > > > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > > > +%YAML 1.2
> > > > +---
> > > > +$id: http://devicetree.org/schemas/display/verisilicon,dc.yaml#
> > > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > > +
> > > > +title: Verisilicon DC-series display controllers
> > > > +
> > > > +maintainers:
> > > > +  - Icenowy Zheng <uwu@...nowy.me>
> > > > +
> > > > +properties:
> > > > +  $nodename:
> > > > +    pattern: "^display@[0-9a-f]+$"
> > > > +
> > > > +  compatible:
> > > > +    const: verisilicon,dc
> > >
> > > This needs an SoC specific compatible. Generally licensed IP
> > > compatibles
> > > are useless because the specs aren't public and there's always
> > > integration quirks.
> >
> > This mimics the GPU IPs by the same vendor, see gpu/vivante,gc.yaml ,
> > which contain the exact same set of identification registers
> > (including
> > a "customer id" one that can differienate the same configured IP on
> > StarFive JH7110 and T-Head TH1520).
> >
> > If we can get vivante,gc to work w/o SoC specific compatible, then we
> > should be able to get verisilicon,dc to work too.
>
> Well maybe I should add etnaviv people to the recipient list, to allow
> them to tell us the magic behind vivante,gc .
>

Vivante GPUs are special because they contain registers that allow them to
be fully identified - see etnaviv_hw_identify(..).

We can read out the following information:
 - model
 - revision
 - product_id
 - customer_id
 - eco_id

This information, in combination with a hardware database (hwdb) in
kernel/userspace, is enough to support these GPUs/NPUs across
different SoC vendors.

-- 
greets
--
Christian Gmeiner, MSc

https://christian-gmeiner.info/privacypolicy