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

Le dim., nov. 7 2021 at 14:43:33 +0100, H. Nikolaus Schaller
<hns@goldelico.com> a écrit :
> Hi,
>
>> Am 05.10.2021 um 22:43 schrieb Paul Cercueil <paul@crapouillou.net>:
>>
>> Hi Nikolaus,
>>
>> Le mar., oct. 5 2021 at 14:29:15 +0200, H. Nikolaus Schaller
>> <hns@goldelico.com> a écrit :
>>> From: Sam Ravnborg <sam@ravnborg.org>
>>> 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@ravnborg.org>
>>> Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
>>> Cc: Rob Herring <robh@kernel.org>
>>> Cc: devicetree@vger.kernel.org
>>> ---
>>> .../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@goldelico.com>
>>> +
>>> +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
>


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