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

From: Lucas Stach <hidden>
Date: 2014-03-24 12:53:47
Also in: linux-arm-kernel, linux-pci, linux-sh

Am Montag, den 24.03.2014, 12:46 +0000 schrieb
Phil.Edworthy-zM6kxYcvzFBBDgjK7y7TUQ@public.gmane.org:

Hi Ben,

On: 24/03/2014 12:25, Phil wrote:

quoted

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

bindings

quoted

Hi Ben,

On: 24/03/2014 12:16, Ben wrote:

quoted

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

bindings

quoted

On 24/03/14 12:04, Phil.Edworthy-zM6kxYcvzFBBDgjK7y7TUQ@public.gmane.org wrote:

quoted

Hi Lucas,

On: 21/03/2014 15:02, Phil wrote:

quoted

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

bindings

quoted

Hi Lucas,

On: 21/03/2014 14:31, Lucas wrote:

quoted

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

tree

quoted

bindings

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Am Freitag, den 21.03.2014, 14:18 +0000 schrieb
Phil.Edworthy-zM6kxYcvzFBBDgjK7y7TUQ@public.gmane.org:

quoted

Hi Lucas,

On 21/03/2014 11:24, Lucas wrote:

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

tree

quoted

bindings

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Am Freitag, den 21.03.2014, 10:32 +0000 schrieb Phil Edworthy:

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This patch adds the bindings for the rcar PCIE driver. The

driver

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resides under drivers/pci/host/pcie-rcar.c

Signed-off-by: Phil Edworthy <redacted>

I have one question below. If you can answer this with yes after
thinking again about it, this is:

Reviewed-by: Lucas Stach <redacted>

quoted

---
  Documentation/devicetree/bindings/pci/rcar-pci.txt | 40

++++++++++++++++++++++

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  1 file changed, 40 insertions(+)
  create mode 100644

Documentation/devicetree/bindings/pci/rcar-pci.txt

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diff --git a/Documentation/devicetree/bindings/pci/rcar-pci.txt

b/

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Documentation/devicetree/bindings/pci/rcar-pci.txt

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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"

quoted

+- 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

quoted

+   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

quoted

PCIe bus clock from it's register clock? No need to enable any

other

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clock for PCIe to work?

Yes, just the one clock. The PCIe bus clock is an external clock

dedicated

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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

quoted

and PCIe. After all you don't want to end up unconditionally

enabling

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this clock from the board or SoC level just to have PCIe working,

right?

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Ok, I see, I'll need a reference to a board clock, even if it's

always

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on for

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these boards.

One small question...

The patches added the PCIe host controller to two devices, r8a7790

and

quoted

r8a7791. The r8a7790-based Lager board doesn't have the necessary

hardware

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to use PCIe, so should I add a dummy pcie_bus clock to the Lager

board

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dts, even though PCIe is not used?

I'm just wondering what the dts file looks like for a board that

doesn't

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support many interfaces. Does it become littered with dummy clocks

and

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regulators?

The bridge node should be set to disabled by default so it never gets
probed. Any boards that want to use it can over-ride the status to be
enabled.

Ok, thanks.

Hmm, yes it doesn't get probed, but you still get a build problem as the 
DT entry references an clock that doesn't exist. Maybe I'm missing 
something...

If the clock is a board supplied one then you have to supply to clocks
property from the board dts, to get rid of the compile failure. You can
not have phandles in the PCIe node referencing a non-existing clock.

Regards,
Lucas
-- 
Pengutronix e.K.                           | Lucas Stach                 |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-5076 |
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