[PATCH v4 5/9] dt-bindings: pci: rcar pcie device tree bindings

[Phil.Edworthy at renesas.com]

Hi Lucas,

On: 21/03/2014 15:02, Phil wrote:
> Subject: Re: [PATCH v4 5/9] dt-bindings: pci: rcar pcie device tree 
bindings
> 
> Hi Lucas,
> 
> On: 21/03/2014 14:31, Lucas wrote:
> > Subject: Re: [PATCH v4 5/9] dt-bindings: pci: rcar pcie device tree 
bindings
> > 
> > Am Freitag, den 21.03.2014, 14:18 +0000 schrieb
> > Phil.Edworthy at renesas.com:
> > > Hi Lucas,
> > > 
> > > On 21/03/2014 11:24, Lucas wrote:
> > > > Subject: Re: [PATCH v4 5/9] dt-bindings: pci: rcar pcie device 
tree 
> > > bindings
> > > > 
> > > > Am Freitag, den 21.03.2014, 10:32 +0000 schrieb Phil Edworthy:
> > > > > This patch adds the bindings for the rcar PCIE driver. The 
driver
> > > > > resides under drivers/pci/host/pcie-rcar.c
> > > > > 
> > > > > Signed-off-by: Phil Edworthy <phil.edworthy at renesas.com>
> > > > 
> > > > I have one question below. If you can answer this with yes after
> > > > thinking again about it, this is:
> > > > 
> > > > Reviewed-by: Lucas Stach <l.stach at pengutronix.de>
> > > > > ---
> > > > >  Documentation/devicetree/bindings/pci/rcar-pci.txt | 40 
> > > ++++++++++++++++++++++
> > > > >  1 file changed, 40 insertions(+)
> > > > >  create mode 100644 
Documentation/devicetree/bindings/pci/rcar-pci.txt
> > > > > 
> > > > > diff --git a/Documentation/devicetree/bindings/pci/rcar-pci.txt 
b/
> > > > Documentation/devicetree/bindings/pci/rcar-pci.txt
> > > > > new file mode 100644
> > > > > index 0000000..0e219b0
> > > > > --- /dev/null
> > > > > +++ b/Documentation/devicetree/bindings/pci/rcar-pci.txt
> > > > > @@ -0,0 +1,40 @@
> > > > > +* Renesas RCar PCIe interface
> > > > > +
> > > > > +Required properties:
> > > > > +- compatible: should contain one of the following
> > > > > +   "renesas,r8a7779-pcie", "renesas,r8a7790-pcie", 
> > > "renesas,r8a7791-pcie"
> > > > > +- reg: base addresses and lengths of the pcie controller.
> > > > > +- #address-cells: set to <3>
> > > > > +- #size-cells: set to <2>
> > > > > +- device_type: set to "pci"
> > > > > +- ranges: ranges for the PCI memory and I/O regions
> > > > > +- interrupts: interrupt values for MSI interrupt
> > > > > +- #interrupt-cells: set to <1>
> > > > > +- interrupt-map-mask and interrupt-map: standard PCI properties
> > > > > +   to define the mapping of the PCIe interface to interrupt
> > > > > +   numbers.
> > > > > +- clocks: from common clock binding: handle to pci clock.
> > > > > +- clock-names: from common clock binding: should be "pcie"
> > > > 
> > > > You really only have one PCIe clock? So the controller is 
generating the
> > > > PCIe bus clock from it's register clock? No need to enable any 
other
> > > > clock for PCIe to work?
> > > Yes, just the one clock. The PCIe bus clock is an external clock 
dedicated 
> > > to PCIe and SATA, and we have no control over it.
> > > 
> > Is this some kind of always-on clock? If not you probably want a
> > reference to it from the PCIe driver even if it's shared between SATA
> > and PCIe. After all you don't want to end up unconditionally enabling
> > this clock from the board or SoC level just to have PCIe working, 
right?
> Ok, I see, I'll need a reference to a board clock, even if it's always 
on for 
> these boards. 
One small question...

The patches added the PCIe host controller to two devices, r8a7790 and 
r8a7791. The r8a7790-based Lager board doesn't have the necessary hardware 
to use PCIe, so should I add a dummy pcie_bus clock to the Lager board 
dts, even though PCIe is not used?

I'm just wondering what the dts file looks like for a board that doesn't 
support many interfaces. Does it become littered with dummy clocks and 
regulators?

Thanks
Phil