Re: [PATCH v2 04/13] ARM: tegra: Add MIPI calibration DT entries for Tegra114

[Thierry Reding <thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

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On Tue, Oct 15, 2013 at 02:41:44PM -0600, Stephen Warren wrote:
> On 10/15/2013 09:27 AM, Thierry Reding wrote:
> > Add a device node for the MIPI calibration block on Tegra114. There is
> > no need to disable it by default because it only enables the clock while
> > performing calibration and therefore shouldn't be consuming any power
> > when unused.
> 
> > diff --git a/arch/arm/boot/dts/tegra114.dtsi b/arch/arm/boot/dts/tegra114.dtsi
> 
> > +	mipi: mipi {
> > +		compatible = "nvidia,tegra114-mipi";
> > +		reg = <0x700e3000 0x100>;
> > +		clocks = <&tegra_car TEGRA114_CLK_MIPI_CAL>;
> > +		#calibrate-cells = <1>;
> > +	};
> 
> Do you have a link to the binding documentation for this? I'm still in
> the dark re: why there's a need for #calibrate-cells at all. It seems
> like this should be some internal implementation detail of the Tegra
> DC/..., or implicit based on the compatible value (if cell count
> changes, just rev the compatible value; it's not like this is a generic
> service for loosely coupled drivers).

Here's the commit that adds the device tree binding:

	https://gitorious.org/thierryreding/linux/commit/43b798a54063156692e0fde2a9022c0ae44b862e

I was under the impression that we needed the #*-cells properties so
that the device tree code could verify that the content is actually
correct and so that it knows how to parse the specifier. I mean why
else do we have the #gpio-cells property for GPIO controller nodes?

Also note that this driver isn't for something internal to the DRM
driver. It can (and will) also be used by the V4L2 camera driver that
Bryan is working on, because the CSI pads need to be calibrated in the
same way.

Thierry

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