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

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Date:   Tue, 2 Jun 2020 17:08:34 +0200
From:   Maxime Ripard <maxime@...no.tech>
To:     Rob Herring <robh@...nel.org>
Cc:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Eric Anholt <eric@...olt.net>, dri-devel@...ts.freedesktop.org,
        linux-rpi-kernel@...ts.infradead.org,
        bcm-kernel-feedback-list@...adcom.com,
        linux-arm-kernel@...ts.infradead.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

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.

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.

Thanks!
Maxime

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