Tegra DRM device tree bindings

[Mark Zhang]

> > On Tue, 26 Jun 2012 12:55:13 +0200
> > Thierry Reding <thierry.reding at avionic-design.de> wrote:
> >
> > > > Old Signed by an unknown key
> > >
> > > Hi,
> > >
> > > while I haven't got much time to work on the actual code right now,
> > > I think it might still be useful if we could get the device tree
> > > binding to a point where everybody is happy with it. That'll also
> > > save me some time once I get to writing the code because I won't
> > > have to redo it over again. =)
> > >
> > > So here's the current proposal:
> > >
> > > 	host1x {
> > > 		compatible = "nvidia,tegra20-host1x", "simple-bus";
> > > 		reg = <0x50000000 0x00024000>;
> > > 		interrupts = <0 64 0x04   /* cop syncpt */
> > > 			      0 65 0x04   /* mpcore syncpt */
> > > 			      0 66 0x04   /* cop general */
> > > 			      0 67 0x04>; /* mpcore general */
> > >
> > > 		#address-cells = <1>;
> > > 		#size-cells = <1>;
> > >
> > > 		ranges = <0x54000000 0x54000000 0x04000000>;
> > >
> > > 		status = "disabled";
> > >
> > > 		gart = <&gart>;
> > ...
> > > output and hooks up a static EDID block with the LVDS output. There
> > > is also a carveout property which might be a better replacement for
> > > the "crippled" GART on Tegra20. Alternatively the CMA might work
> > > just as well instead.
> > >
> > > The Plutux can be described like this:
> > >
> > > 	host1x {
> > > 		carveout = <0x0e000000 0x02000000>;
> >
> > As discussed in the following ML thread previously, the necessary info
> > related to the "gart" would be got from the standard IOMMU API(or
> > something above layers, DMABUF or TTM?). So I don't think that we need
> > to refer to "gart" and "carveout" here in the end.
> >
> > http://lists.linuxfoundation.org/pipermail/iommu/2012-June/004266.html
> 
> Yes, if IOMMU or some layer above can provide the same information, then that
> is certainly better than explicitly referencing it in the DT.
> 
> I'm not sure I understand how information about the carveout would be
> obtained from the IOMMU API, though.

I think that can be similar with current gart implementation. Define carveout as: 

carveout {
        compatible = "nvidia,tegra20-carveout";
        size = <0x10000000>;
};

Then create a file such like "tegra-carveout.c" to get these definitions and register itself as platform device's iommu instance.

> 
> Thierry
> 
> * Unknown Key
> * 0x7F3EB3A1