ARM: shmobile: Define DT bindings for timer devices

The SH mobile series currently features 3 timer devices in the kernel:
Compare Match Timer (CMT), Timer Unit (TMU) and MTU2. These devices
share register layout characteristics amongst each that enable us to
define common DT bindings for them.

Signed-off-by: Bastian Hecht <hechtb+renesas@gmail.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

diff --git a/Documentation/devicetree/bindings/timer/renesas,timer.txt b/Documentation/devicetree/bindings/timer/renesas,timer.txt
new file mode 100644 (file)
index 0000000..2c001bf
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+++ b/Documentation/devicetree/bindings/timer/renesas,timer.txt
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+* Renesas SH Mobile Timer
+
+Bindings for several timer devices from Renesas including CMT, TMU and MTU2.
+
+Required properties:
+- compatible : Should be "renesas,{device}-timer",
+  whereas device is "cmt", "tmu" or "mtu2".
+- reg : Address and length of the register set for the device
+- interrupts : Timer interrupt
+- renesas,device-id : The ID of the timer device
+- renesas,channel-id : The channel ID of the timer device
+- renesas,source-quality : The viability to use this device as a free
+  running clock. From 0 (do not use) to 10 (best possible clock).
+- renesas,event-quality : The viability to use this device as an event
+  generator. From 0 (do not use) to 10 (best possible clock).
+
+The properties renesas,{source,event}-quality reflect the situation that the
+usability of the timer devices depend on the location within their SoCs. E.g.
+the power domain affinty affects power management, some mux-ed lines might be
+preferred to be assigned to other functions and other constraints.
+
+Example for CMT1 channel 0 on the R8A7740 SoC:
+
+       timer@e6138010 {
+               compatible = "renesas,cmt-timer";
+               interrupt-parent = <&intca>;
+               reg = <0xe6138010 0xc>;
+               interrupts = <0x0b00>;
+               renesas,device-id = <1>;
+               renesas,channel-id = <0>;
+               renesas,source-quality = <3>;
+               renesas,event-quality = <3>;
+       };
+
+Example for TMU0 channel 1 on the SH7372 SoC:
+       timer@fff60014 {
+               compatible = "renesas,tmu-timer";
+               interrupt-parent = <&intcs>;
+               reg = <0xfff60014 0xc>;
+               interrupts = <0xea0>;
+               renesas,device-id = <0>;
+               renesas,channel-id = <1>;
+               renesas,source-quality = <4>;
+               renesas,event-quality = <0>;
+       };