Re: [PATCH v3 1/2] dt-bindings: drm/bridge: adv7511: Add regulator bindings

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Archit,

(CC'ing Mark Brown)

On Tuesday 29 Nov 2016 13:41:33 Archit Taneja wrote:
> On 11/29/2016 12:03 PM, Laurent Pinchart wrote:
> > On Tuesday 29 Nov 2016 11:37:41 Archit Taneja wrote:
> >> Add the regulator supply properties needed by ADV7511 and ADV7533.
> >> 
> >> The regulators are specified as optional properties since there can
> >> be boards which have a fixed supply directly routed to the pins, and
> >> these may not be modelled as regulator supplies.
> > 
> > That's why we have support for dummy supplies in the kernel, isn't it ?
> > Isn't it better to make the supplies mandatory in the bindings (and
> > obviously handling them as optional in the driver for
> > backward-compatibility) ?
>
> I'm a bit unclear on this.
> 
> I thought we couldn't add mandatory properties once the device is already
> present in DT for one or more platforms.

You can, as long as you treat them as optional in the driver to retain 
backward compatibility. The DT bindings should document the properties 
expected from a new platform (older versions of the bindings will always be 
available in the git history).

> Say, if we do make it mandatory for future additions, we would need to have
> DT property for the supplies for the new platforms. If the regulators on
> these boards are fixed supplies, they would be need to be modeled
> using "regulator-fixed", possibly without any input supply. Is that
> what you're suggesting?

That's the idea, yes. Clock maintainers have a similar opinion regarding the 
clock bindings, where a clock that is not optional at the hardware level 
should be specified in DT even if it's always present.

Mark, any opinion ?

> > Apart from that,
> > 
> > Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > 
> >> Cc: devicetree@vger.kernel.org
> >> Acked-by: Rob Herring <robh@kernel.org>
> >> Signed-off-by: Archit Taneja <architt@codeaurora.org>
> >> ---
> >> v3:
> >> - Revert back to having a common avdd-supply property for the 1.8V
> >>   supplies
> >> 
> >> Documentation/devicetree/bindings/display/bridge/adi,adv7511.txt | 9 ++++
> >> 1 file changed, 9 insertions(+)
> >> 
> >> diff --git
> >> a/Documentation/devicetree/bindings/display/bridge/adi,adv7511.txt
> >> b/Documentation/devicetree/bindings/display/bridge/adi,adv7511.txt index
> >> 6532a59..13d53bc 100644
> >> --- a/Documentation/devicetree/bindings/display/bridge/adi,adv7511.txt
> >> +++ b/Documentation/devicetree/bindings/display/bridge/adi,adv7511.txt
> >> 
> >> @@ -56,6 +56,15 @@ Optional properties:
> >>  - adi,disable-timing-generator: Only for ADV7533. Disables the internal
> >> 
> >> timing generator. The chip will rely on the sync signals in the DSI data
> >> lanes, rather than generate its own timings for HDMI output.
> >> +- avdd-supply: A common 1.8V supply that powers up the AVDD, DVDD and
> >> PVDD
> >> +  pins. On ADV7511, it also feeds to the BGVDD pin. On ADV7533, it also
> >> powers
> >> +  up the A2VDD pin.
> >> +- v3p3-supply: A 3.3V supply that powers up the pin called DVDD_3V on
> >> +  ADV7511 and V3P3 on ADV7533.
> >> +
> >> +ADV7533 specific supplies:
> >> +- v1p2-supply: A supply that powers up the V1P2 pin on the chip. It can
> >> be
> >> +  either 1.2V or 1.8V.
> >> 
> >>  Required nodes:

-- 
Regards,

Laurent Pinchart

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