linux-kernel - Re: [PATCH v3 104/105] dt-bindings: display: vc4: hdmi: Add BCM2711 HDMI controllers bindings

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Message-ID: <CAL_JsqJShNcyUDv1JmdanLKZqFa0TeJGazwmPz6eJ_Rq0GtkpQ@mail.gmail.com>
Date:   Mon, 8 Jun 2020 17:01:41 -0600
From:   Rob Herring <robh@...nel.org>
To:     Maxime Ripard <maxime@...no.tech>
Cc:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Eric Anholt <eric@...olt.net>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        "moderated list:BROADCOM BCM2835 ARM ARCHITECTURE" 
        <linux-rpi-kernel@...ts.infradead.org>,
        "maintainer:BROADCOM BCM7XXX ARM ARCHITECTURE" 
        <bcm-kernel-feedback-list@...adcom.com>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        Tim Gover <tim.gover@...pberrypi.com>,
        Phil Elwell <phil@...pberrypi.com>, devicetree@...r.kernel.org
Subject: Re: [PATCH v3 104/105] dt-bindings: display: vc4: hdmi: Add BCM2711
 HDMI controllers bindings

On Tue, Jun 2, 2020 at 9:08 AM Maxime Ripard <maxime@...no.tech> wrote:
>
> Hi Rob,
>
> On Fri, May 29, 2020 at 12:18:33PM -0600, Rob Herring wrote:
> > On Wed, May 27, 2020 at 05:49:14PM +0200, Maxime Ripard wrote:
> > > The HDMI controllers found in the BCM2711 SoC need some adjustments to the
> > > bindings, especially since the registers have been shuffled around in more
> > > register ranges.
> > >
> > > Cc: Rob Herring <robh+dt@...nel.org>
> > > Cc: devicetree@...r.kernel.org
> > > Signed-off-by: Maxime Ripard <maxime@...no.tech>
> > > ---
> > >  Documentation/devicetree/bindings/display/brcm,bcm2711-hdmi.yaml | 109 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
> > >  1 file changed, 109 insertions(+)
> > >  create mode 100644 Documentation/devicetree/bindings/display/brcm,bcm2711-hdmi.yaml
> > >
> > > diff --git a/Documentation/devicetree/bindings/display/brcm,bcm2711-hdmi.yaml b/Documentation/devicetree/bindings/display/brcm,bcm2711-hdmi.yaml
> > > new file mode 100644
> > > index 000000000000..6091fe3d315b
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/display/brcm,bcm2711-hdmi.yaml
> > > @@ -0,0 +1,109 @@
> > > +# SPDX-License-Identifier: GPL-2.0
> >
> > Dual license...
> >
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/display/brcm,bcm2711-hdmi.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: Broadcom BCM2711 HDMI Controller Device Tree Bindings
> > > +
> > > +maintainers:
> > > +  - Eric Anholt <eric@...olt.net>
> > > +
> > > +properties:
> > > +  compatible:
> > > +    enum:
> > > +      - brcm,bcm2711-hdmi0
> > > +      - brcm,bcm2711-hdmi1
> >
> > What's the difference between the 2 blocks?
>
> The register layout and the lane mapping in the PHY change a bit.
>
> > > +
> > > +  reg:
> > > +    items:
> > > +      - description: HDMI controller register range
> > > +      - description: DVP register range
> > > +      - description: HDMI PHY register range
> > > +      - description: Rate Manager register range
> > > +      - description: Packet RAM register range
> > > +      - description: Metadata RAM register range
> > > +      - description: CSC register range
> > > +      - description: CEC register range
> > > +      - description: HD register range
> > > +
> > > +  reg-names:
> > > +    items:
> > > +      - const: hdmi
> > > +      - const: dvp
> > > +      - const: phy
> > > +      - const: rm
> > > +      - const: packet
> > > +      - const: metadata
> > > +      - const: csc
> > > +      - const: cec
> > > +      - const: hd
> > > +
> > > +  clocks:
> > > +    description: The HDMI state machine clock
> > > +
> > > +  clock-names:
> > > +    const: hdmi
> > > +
> > > +  ddc:
> > > +    allOf:
> > > +      - $ref: /schemas/types.yaml#/definitions/phandle
> > > +    description: >
> > > +      Phandle of the I2C controller used for DDC EDID probing
> >
> > Goes in the connector.
> >
> > And isn't the standard name ddc-i2c-bus?
> >
> > > +
> > > +  hpd-gpios:
> > > +    description: >
> > > +      The GPIO pin for the HDMI hotplug detect (if it doesn't appear
> > > +      as an interrupt/status bit in the HDMI controller itself)
> >
> > Goes in the connector.
>
> If this was an entirely new binding, I would agree, but this is not
> really the case here.
>
> We discussed it already for the v2, and this binding is essentially the
> same one than the bcm2835 HDMI controller.
>
> I initially sent a patch adding conditionnals for the clocks and regs
> differences too, and you asked to split the binding into a separate file
> to simplify it a bit.

Ah... Best to assume I don't remember what happened last week. ;)

> Supporting both the old binding, and the new one based on the connector
> is going to make the code significantly more complicated, and I'm not
> really sure why we would here.

I'm not really sure I agree on the complexity, but that can be a
discussion for another day.

Reviewed-by: Rob Herring <robh@...nel.org>

Rob