Re: [PATCH 1/2] dt-bindings: media: Add Cadence MIPI-CSI2RX Device Tree bindings

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 




Hi Rob,

Sorry for the slow answer.

On Fri, Jul 07, 2017 at 11:21:05AM -0500, Rob Herring wrote:
> On Mon, Jul 03, 2017 at 02:40:22PM +0200, Maxime Ripard wrote:
> > The Cadence MIPI-CSI2 RX controller is a CSI2RX bridge that supports up to
> > 4 CSI-2 lanes, and can route the frames to up to 4 streams, depending on
> > the hardware implementation.
> 
> Streams and lanes are separate, right? Do you need to know how many 
> lanes are configured/connected?

Streams are the output interfaces, lanes are in input. The number of
lanes used is basically defined by the device attached to the other
side, and each device can use between 1 to 4 lanes, depending on the
device.

On those lanes, the CSI protocol defines virtual channels, usually to
support multiple devices on the same set of lanes. This device is then
able to route the virtual channels in input to any of its streams in
output.

It doesn't really matter how many lanes are configured or connected,
beside some basic setup, and this is already described through the
media additions to the OF-graph through a property of the link.

What matters is how many streams you have in output to know your
routing options, and the number of virtual channels you will have, but
that's dynamic iirc.

> > It can operate with an external D-PHY, an internal one or no D-PHY at all
> > in some configurations.
> > 
> > Signed-off-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>
> > ---
> >  .../devicetree/bindings/media/cdns-csi2rx.txt      | 87 ++++++++++++++++++++++
> >  1 file changed, 87 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/media/cdns-csi2rx.txt
> > 
> > diff --git a/Documentation/devicetree/bindings/media/cdns-csi2rx.txt b/Documentation/devicetree/bindings/media/cdns-csi2rx.txt
> > new file mode 100644
> > index 000000000000..b5bcb6ad18fc
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/media/cdns-csi2rx.txt
> > @@ -0,0 +1,87 @@
> > +Cadence CSI2RX controller
> > +=========================
> > +
> > +The Cadence CSI2RX controller is a CSI-2 bridge supporting up to 4 CSI
> > +lanes in input, and 4 different pixel streams in output.
> > +
> > +Required properties:
> > +  - compatible: must be set to "cdns,csi2rx"
> 
> Should have a "and an SoC specific compatible string" statement.

Ok.

> > +  - reg: base address and size of the memory mapped region
> > +  - clocks: phandles to the clocks driving the controller
> > +  - clock-names: must contain:
> > +    * sys_clk: main clock
> > +    * p_clk: register bank clock
> > +    * p_free_clk: free running register bank clock
> > +    * pixel_ifX_clk: pixel stream output clock, one for each stream
> > +                     implemented in hardware, between 0 and 3
> > +    * dphy_rx_clk: D-PHY byte clock, if implemented in hardware
> 
> "if implemented in hardare" means internal D-PHY?

It means if we have a D-PHY, either internal or external. In the case
where we don't have any D-PHY, then we'll obviously won't have that
clock.

> > +  - phys: phandle to the external D-PHY
> > +  - phy-names: must contain dphy, if the implementation uses an
> > +               external D-PHY
> 
> If? Should phys/phy-names be optional?

Yes and no, and I don't really know how it's usually handled in the
documentation. The property is mandatory if the hardware uses a
D-PHY. But it shouldn't be there if it doesn't. So it's not really
optional, it's mandatory in one case, and useless in the other.

Thanks!
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

Attachment: signature.asc
Description: PGP signature


[Index of Archives]     [Device Tree Compilter]     [Device Tree Spec]     [Linux Driver Backports]     [Video for Linux]     [Linux USB Devel]     [Linux PCI Devel]     [Linux Audio Users]     [Linux Kernel]     [Linux SCSI]     [XFree86]     [Yosemite Backpacking]


  Powered by Linux