Re: [PATCH v3 1/2] dt-bindings: display: bridge: add TI TDP158

[Marc Gonzalez <mgonzalez@freebox.fr>]

On 27/06/2024 18:25, Conor Dooley wrote:

> On Thu, Jun 27, 2024 at 01:13:03PM +0200, Marc Gonzalez wrote:
>
>> TDP158 is an AC-coupled DVI / HDMI to TMDS level shifting Redriver.
>> It supports DVI 1.0, HDMI 1.4b and 2.0b.
>> It supports 4 TMDS channels, HPD, and a DDC interface.
>> It supports dual power supply rails (1.1V on VDD, 3.3V on VCC)
>> for power reduction. Several methods of power management are
>> implemented to reduce overall power consumption.
>> It supports fixed receiver EQ gain using I2C or pin strap to
>> compensate for different lengths input cable or board traces.
>>
>> Features
>>
>> - AC-coupled TMDS or DisplayPort dual-mode physical layer input
>> to HDMI 2.0b TMDS physical layer output supporting up to 6Gbps
>> data rate, compatible with HDMI 2.0b electrical parameters
>> - DisplayPort dual-mode standard version 1.1
>> - Programmable fixed receiver equalizer up to 15.5dB
>> - Global or independent high speed lane control, pre-emphasis
>> and transmit swing, and slew rate control
>> - I2C or pin strap programmable
>> - Configurable as a DisplayPort redriver through I2C
>> - Full lane swap on main lanes
>> - Low power consumption (200 mW at 6Gbps, 8 mW in shutdown)
>>
>> https://www.ti.com/lit/ds/symlink/tdp158.pdf
>>
>> Signed-off-by: Marc Gonzalez <mgonzalez@freebox.fr>
>> ---
>>  .../bindings/display/bridge/ti,tdp158.yaml         | 51 ++++++++++++++++++++++
>>  1 file changed, 51 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/display/bridge/ti,tdp158.yaml b/Documentation/devicetree/bindings/display/bridge/ti,tdp158.yaml
>> new file mode 100644
>> index 0000000000000..21c8585c3bb2d
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/display/bridge/ti,tdp158.yaml
>> @@ -0,0 +1,51 @@
>> +# SPDX-License-Identifier: GPL-2.0-only
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/display/bridge/ti,tdp158.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: TI TDP158 HDMI to TMDS Redriver
>> +
>> +maintainers:
>> +  - Arnaud Vrac <avrac@freebox.fr>
>> +  - Pierre-Hugues Husson <phhusson@freebox.fr>
>> +
>> +properties:
>> +  compatible:
>> +    const: ti,tdp158
>> +
>> +  reg:
>> +    description: I2C address of the device
> 
> Is reg not required? How do you communicate with the device if the i2c
> bus is not connected? Is the enable GPIO enough to operate it in some
> situations?
> 
> Otherwise this looks good to me, but given Maxime commented about the
> complexity of the device, I'm probably out of my depth!

Valid question.

As discussed in my brilliantly expanded commit message (:p)
the device can be configured in various ways, either through I2C registers
or by pin strap. We use the device in its default settings, so we don't
touch any I2C registers, thus I'm not sure the reg property is required.

>> +required:
>> +  - compatible
>> +  - vcc-supply
>> +  - vdd-supply
>> +  - ports


Regards