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

Bjorn Andersson bjorn.andersson at linaro.org
Mon Dec 5 21:11:51 UTC 2016

On Tue 29 Nov 01:11 PST 2016, Laurent Pinchart wrote:

> 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).

If you document them as required and don't do anything special in the
implementation (i.e. just call devm_regulator_get() as usual) it will
just work, in the absence of the property you will get a dummy regulator
from the framework.

And then add the fixed-voltage regulators to the new DT to make that
properly describe the hardware.

> > 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.

Further more, a DT binding for a particular block should describe that
block; so if we have three different 1.8V pins then the DT binding
should reflect this - even if our current platform have them wired to
the same regulator.

(And the supply names would preferably be based on the pin names in the
component data sheet)


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