Re: [PATCH v5 3/7] dt-bindings: display: Add ingenic,jz4780-dw-hdmi DT Schema

[Paul Cercueil]

Hi Nikolaus,

Le dim., nov. 7 2021 at 14:43:33 +0100, H. Nikolaus Schaller 
<hns@xxxxxxxxxxxxx> a écrit :
> Hi,
>
> >  Am 05.10.2021 um 22:43 schrieb Paul Cercueil <paul@xxxxxxxxxxxxxxx>:
> >
> >  Hi Nikolaus,
> >
> >  Le mar., oct. 5 2021 at 14:29:15 +0200, H. Nikolaus Schaller 
> > <hns@xxxxxxxxxxxxx> a écrit :
> > >  From: Sam Ravnborg <sam@xxxxxxxxxxxx>
> > >  Add DT bindings for the hdmi driver for the Ingenic JZ4780 SoC.
> > >  Based on .txt binding from Zubair Lutfullah Kakakhel
> > >  Signed-off-by: Sam Ravnborg <sam@xxxxxxxxxxxx>
> > >  Signed-off-by: H. Nikolaus Schaller <hns@xxxxxxxxxxxxx>
> > >  Cc: Rob Herring <robh@xxxxxxxxxx>
> > >  Cc: devicetree@xxxxxxxxxxxxxxx
> > >  ---
> > >  .../bindings/display/ingenic-jz4780-hdmi.yaml | 79 
> > > +++++++++++++++++++
> > >  1 file changed, 79 insertions(+)
> > >  create mode 100644 
> > > Documentation/devicetree/bindings/display/ingenic-jz4780-hdmi.yaml
> > >  diff --git 
> > > a/Documentation/devicetree/bindings/display/ingenic-jz4780-hdmi.yaml 
> > > b/Documentation/devicetree/bindings/display/ingenic-jz4780-hdmi.yaml
> > >  new file mode 100644
> > >  index 000000000000..5bcb342da86f
> > >  --- /dev/null
> > >  +++ 
> > > b/Documentation/devicetree/bindings/display/ingenic-jz4780-hdmi.yaml
> > >  @@ -0,0 +1,79 @@
> > >  +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > >  +%YAML 1.2
> > >  +---
> > >  +$id: 
> > > http://devicetree.org/schemas/display/ingenic-jz4780-hdmi.yaml#
> > >  +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > >  +
> > >  +title: Bindings for Ingenic JZ4780 HDMI Transmitter
> > >  +
> > >  +maintainers:
> > >  +  - H. Nikolaus Schaller <hns@xxxxxxxxxxxxx>
> > >  +
> > >  +description: |
> > >  +  The HDMI Transmitter in the Ingenic JZ4780 is a Synopsys 
> > > DesignWare HDMI 1.4
> > >  +  TX controller IP with accompanying PHY IP.
> >
> >  My dmesg disagrees:
> >  dw-hdmi-ingenic 10180000.hdmi: Detected HDMI TX controller v1.31a 
> > with HDCP (DWC HDMI 3D TX PHY)
>
> mine as well.
>
> >  Or am I comparing apples to oranges?
>
> There is a document called "JZ4780 High Efficiency Engine for Mobile 
> Device"
> (JZ4780_PB.pdf) which says
>
> "24-bit parallel/serial TFT interface, HDMI 1.4a interface, LVDS 
> interface"
>
> And the data sheet ("JZ4780 Mobile Application Processor Data Sheet 
> ") says: "Support HDMI 1.4a Interface"
>
> Finally, the programming manual also says "Support HDMI 1.4a 
> Interface".
>
> So what is correct?
>
> dmesg may return something else. E.g. silicon revision 1.31a
> while the interface is HDMI protocol revision 1.4a compatible?
>
> Trying to find something about "hdmi 1.31a" did only lead to some
> "Synopsys' HAPS-51 eval platform" [1].
>
> Looking at HDMI standards [2] I can only find HDMI 1.3 and 1.3a but 
> no HDMI 1.31a.
>
> [1] 
> https://www.digital-cp.com/hdcp-products/haps51-hdmi-tx-platform-dwc-hdmi-tx-controller-131a-ea-hdmi-3d-tx-phy-tsmc40g-ip
> [2] https://en.wikipedia.org/wiki/HDMI#Version_1.3
>
> Well it may also be some Synopsys-internal designation 1.31a 
> referring so something
> newer than HDMI 1.3a which became the HDMI 1.4 standard (released 
> June 2009)...
>
> Whom should we believe? What the chip tells or what the data sheet 
> and programming
> manual says?
>
> I tend to keep confusion low and stay with "HDMI 1.4" in the bindings 
> because
> there is no offical "HDMI 1.31a" standard. And HDMI 1.4 was already 
> some years old
> when the jz4780 was released. So it is likely that the chip 
> identification just
> returns 1.31a (maybe Ingenic licenced an interim release VHDL) 
> although the standard
> was later officially named 1.4a.

Fair enough. Let's keep "HDMI 1.4" until proven otherwise.

Cheers,
-Paul

> > >  +
> > >  +allOf:
> > >  +  - $ref: bridge/synopsys,dw-hdmi.yaml#
> > >  +
> > >  +properties:
> > >  +  compatible:
> > >  +    const: ingenic,jz4780-dw-hdmi
> > >  +
> > >  +  reg-io-width:
> > >  +    const: 4
> > >  +
> > >  +  clocks:
> > >  +    maxItems: 2
> > >  +
> > >  +  hdmi-5v-supply:
> > >  +    description: Optional regulator to provide +5V at the 
> > > connector
> > >  +
> > >  +  ddc-i2c-bus:
> > >  +    description: An I2C interface if the internal DDC I2C driver 
> > > is not to be used
> >
> >  This property is used within 
> > (drivers/gpu/drm/bridge/synopsys/dw-hdmi.c); I think it would make 
> > sense to move it to bridge/synopsys,dw-hdmi.yaml.
>
> It is indeed more general and not jz4780 specific. I'll move it for 
> v6.
>
> BR and thanks,
> Nikolaus