Re: [PATCH v2 1/2] dt-bindings: display: bridge: add TI TDP158

[Conor Dooley <conor@kernel.org>]

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On Wed, Jun 26, 2024 at 07:20:46PM +0200, Marc Gonzalez wrote:
> On 26/06/2024 18:08, Conor Dooley wrote:
> 
> > On Tue, Jun 25, 2024 at 06:38:12PM +0200, Marc Gonzalez wrote:
> >
> >> The TI TDP158 is an HDMI to TMDS Redriver.
> >>
> >> Signed-off-by: Marc Gonzalez <mgonzalez@freebox.fr>
> >> ---
> >>  .../bindings/display/bridge/ti,tdp158.yaml         | 48 ++++++++++++++++++++++
> >>  1 file changed, 48 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..b687699e2ba80
> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/display/bridge/ti,tdp158.yaml
> >> @@ -0,0 +1,48 @@
> >> +# 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>
> >> +
> >> +properties:
> >> +  compatible:
> >> +    const: ti,tdp158
> >> +
> >> +  reg:
> >> +    description: I2C address of the device
> >> +
> >> +  enable-gpios:
> >> +    description: GPIO controlling bridge enable
> >> +
> >> +  vcc-supply:
> >> +    description: Power supply 3.3V
> >> +
> >> +  vdd-supply:
> >> +    description: Power supply 1.1V
> > 
> > Are these supplies not also required? Surely the device needs the power
> > to function?
> 
> Maybe if the hamsters spin fast enough in their wheels,
> these supplies won't be required? :)
> 
> The reason I hesitated to mark them as required,
> is because the HW engineer told us that on our board
> they were connected to a power line that is shared
> between several functional blocks.
> 
> I suppose that's not a reason?

Then all of those blocks should have their supplies described in the
devicetree! FWIW, if you don't put them in your dts, you'll get
validation failures but the regulator core will produce dummy regulators
so your driver should "just workTM". I'd suggest that you add the
supplies though to these other functional blocks so that the OS can
manage them properly.

> Required means "device doesn't work if they're not connected" ?

Correct.

Thanks,
Conor.


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