Re: [PATCH 4/4] ARM: kirkwood: convert orion-wdt to fdt.

On Fri, Mar 02, 2012 at 10:15:11AM +0100, Simon Guinot wrote:

Hi Jason,

On Thu, Mar 01, 2012 at 06:20:55PM +0000, Jason Cooper wrote:

quoted

Converted register address to a variable so that it could be set from
fdt.  Also, pull clock frequency from fdt and clean up failure logic a
bit.

Same as rtc-mv, this device is used in all kirkwood boards.  So, it is
placed in kirkwood.dtsi.

Signed-off-by: Jason Cooper <redacted>
---
 arch/arm/boot/dts/kirkwood.dtsi   |    6 +++++
 arch/arm/mach-kirkwood/board-dt.c |    1 -
 arch/arm/mach-kirkwood/common.c   |    2 +-
 arch/arm/mach-kirkwood/common.h   |    1 -
 drivers/watchdog/orion_wdt.c      |   44 ++++++++++++++++++++++++++----------
 5 files changed, 39 insertions(+), 15 deletions(-)

diff --git a/arch/arm/boot/dts/kirkwood.dtsi b/arch/arm/boot/dts/kirkwood.dtsi
index 5fb185c..bf28424 100644
--- a/arch/arm/boot/dts/kirkwood.dtsi
+++ b/arch/arm/boot/dts/kirkwood.dtsi

@@ -8,5 +8,11 @@
 		reg = <0xf1010300 0x1f>;
 		interrupts = <53>;
 	};
+
+	wdt@fed20300 {
+		compatible = "marvell,orion-wdt";
+		reg = <0xfed20300 0x28>;
+		clock-frequency = <200000000>;
+	};

How this will work for boards using a different clock frequency (TCLK) ?
Here, we could have 166MHz for example.

Can this node be updated during the board initialization with a detected
TCLK value ?

Or maybe this clock-frequency can reference a TCLK frequency defined in
a board specific dts (I don't know if the DT format allow such things) ?

Grr... good catch.  I originally had this in kirkwood-dreamplug.dts,
which is always 200000000.  That's not the case in kirkwood.dtsi.  What
I would like to do, and I haven't had time to look into it (I thought I
would tackle it later as a refinement :-( ), is a reference of some
sort, eg:

in kirkwood.dtsi:

/ {
	compatible = "marvell,kirkwood";
	tclk:clock-frequency = <200000000>;

	wdt@fed20300 {
		compatible = "marvell,orion-wdt";
		reg = <0xfed20300 0x28>;
		clock-frequency = &tclk;
	};
};

then, in kirkwood-foobar.dts

/include/ "kirkwood.dtsi"

/ {
	model = "foobar";
	compatible = "...";
	tclk:clock-frequency = <166000000>;
};

but I'm not sure if that would work.

In any case, the simplest answer is to set clock-frequency in
kirkwood-dreamplug.dts as a root node property, and then each driver
that needs tclk, requests the clock-frequency from the root node.
Hopefully, Grant can chime in on this one.

Thanks for the review,

Jason.