On Fri, 5 Oct 2012, Sascha Hauer wrote:
> On Fri, Oct 05, 2012 at 05:41:00PM +0200, Guennadi Liakhovetski wrote:
> > Hi Sascha
> >
> > > > +
> > > > + ceu0: ceu@0xfe910000 {
> > > > + compatible = "renesas,sh-mobile-ceu";
> > > > + reg = <0xfe910000 0xa0>;
> > > > + interrupts = <0x880>;
> > > > +
> > > > + mclk: master_clock {
> > > > + compatible = "renesas,ceu-clock";
> > > > + #clock-cells = <1>;
> > > > + clock-frequency = <50000000>; /* max clock frequency */
> > > > + clock-output-names = "mclk";
> > > > + };
> > > > +
> > > > + port {
> > > > + #address-cells = <1>;
> > > > + #size-cells = <0>;
> > > > +
> > > > + ceu0_1: link@1 {
> > > > + reg = <1>; /* local link # */
> > > > + remote = <&ov772x_1_1>; /* remote phandle */
> > > > + bus-width = <8>; /* used data lines */
> > > > + data-shift = <0>; /* lines 7:0 are used */
> > > > +
> > > > + /* If [hv]sync-active are missing, embedded bt.605 sync is used */
> > > > + hsync-active = <1>; /* active high */
> > > > + vsync-active = <1>; /* active high */
> > > > + data-active = <1>; /* active high */
> > > > + pclk-sample = <1>; /* rising */
> > > > + };
> > > > +
> > > > + ceu0_0: link@0 {
> > > > + reg = <0>;
> > > > + remote = <&csi2_2>;
> > > > + immutable;
> > > > + };
> > > > + };
> > > > + };
> > > > +
> > > > + i2c0: i2c@0xfff20000 {
> > > > + ...
> > > > + ov772x_1: camera@0x21 {
> > > > + compatible = "omnivision,ov772x";
> > > > + reg = <0x21>;
> > > > + vddio-supply = <®ulator1>;
> > > > + vddcore-supply = <®ulator2>;
> > > > +
> > > > + clock-frequency = <20000000>;
> > > > + clocks = <&mclk 0>;
> > > > + clock-names = "xclk";
> > > > +
> > > > + port {
> > > > + /* With 1 link per port no need in addresses */
> > > > + ov772x_1_1: link {
> > > > + bus-width = <8>;
> > > > + remote = <&ceu0_1>;
> > > > + hsync-active = <1>;
> > > > + vsync-active = <0>; /* who came up with an inverter here?... */
> > > > + data-active = <1>;
> > > > + pclk-sample = <1>;
> > > > + };
> > >
> > > I currently do not understand why these properties are both in the sensor
> > > and in the link. What happens if they conflict? Are inverters assumed
> > > like suggested above? I think the bus can only have a single bus-width,
> > > why allow multiple bus widths here?
> >
> > Yes, these nodes represent port configuration of each party on a certain
> > link. And they can differ in certain properties, like - as you correctly
> > notice - in the case, when there's an inverter on a line. As for other
> > properties, some of them must be identical, like bus-width, still, they
> > have to be provided on both ends, because generally drivers have to be
> > able to perform all the required configuration based only on the
> > information from their own nodes, without looking at "remote" partner node
> > properties.
>
> So the port associated to the ov772x_1 only describes how to configure
> the ov772x and it's up to me to make sure that this configuration
> matches the partner device. If I don't then it won't work but soc-camera
> will happily continue.
> Ok, that's good, I thought there would be some kind of matching
> mechanism take place here. It may be worth to make this more explicit in
> the docs.
>
> >
> > > > + reg = <0xffc90000 0x1000>;
> > > > + interrupts = <0x17a0>;
> > > > + #address-cells = <1>;
> > > > + #size-cells = <0>;
> > > > +
> > > > + port@1 {
> > > > + compatible = "renesas,csi2c"; /* one of CSI2I and CSI2C */
> > > > + reg = <1>; /* CSI-2 PHY #1 of 2: PHY_S, PHY_M has port address 0, is unused */
> > > > +
> > > > + csi2_1: link {
> > > > + clock-lanes = <0>;
> > > > + data-lanes = <2>, <1>;
> > > > + remote = <&imx074_1>;
> > > > + };
> > > > + };
> > > > + port@2 {
> > > > + reg = <2>; /* port 2: link to the CEU */
> > > > +
> > > > + csi2_2: link {
> > > > + immutable;
> > > > + remote = <&ceu0_0>;
> > > > + };
> > > > + };
> > >
> > > Maybe the example would be clearer if you split it up in two, one simple
> > > case with the csi2_1 <-> imx074_1 and a more advanced with the link in
> > > between.
> >
> > With no link between two ports no connection is possible, so, only
> > examples with links make sense.
>
> I should have said with the renesas,sh-mobile-ceu in between.
>
> So simple example: csi2_1 <-l-> imx074_1
> advanced: csi2_2 <-l-> ceu <-l-> ov772x
No, CEU is the DMA engine with some image processing, so, it's always
present. The CSI-2 is just a MIPI CSI-2 interface, that in the above case
is used with the CEU too. So, it's like
,-l- ov772x
/
ceu0 <
\
`-l- csi2 -l- imx074
> > > It took me some time until I figured out that these are two
> > > separate camera/sensor pairs. Somehow I was looking for a multiplexer
> > > between them.
> >
> > Maybe I can add more comments to the file, perhaps, add an ASCII-art
> > chart.
>
> That would be good.
Is the above good enough? :)
Thanks
Guennadi
> > > I am not sure we really want to have these circular phandles here.
> >
> > It has been suggested and accepted during a discussion at the KS / LPC a
> > month ago. The original version only had phandle referencing in one
> > direction.
>
> Ok.
>
> Sascha
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/
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