DEVICETREE: Add Ingenic CGU binding documentation

Document the devicetree binding for Ingenic SoC CGUs, and add headers
defining the clock specifiers for clocks provided by the JZ4740 & JZ4780
CGU blocks.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: Ian Campbell <ijc+devicetree@hellion.org.uk>
Cc: Kumar Gala <galak@codeaurora.org>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mike Turquette <mturquette@linaro.org>
Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: devicetree@vger.kernel.org
Cc: linux-mips@linux-mips.org
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/10152/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 53 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/clock/ingenic,cgu.txt b/Documentation/devicetree/bindings/clock/ingenic,cgu.txt
new file mode 100644
index 000000000000..f8d4134ae409
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/ingenic,cgu.txt
@@ -0,0 +1,53 @@
+Ingenic SoC CGU binding
+
+The CGU in an Ingenic SoC provides all the clocks generated on-chip. It
+typically includes a variety of PLLs, multiplexers, dividers & gates in order
+to provide many different clock signals derived from only 2 external source
+clocks.
+
+Required properties:
+- compatible : Should be "ingenic,<soctype>-cgu".
+  For example "ingenic,jz4740-cgu" or "ingenic,jz4780-cgu".
+- reg : The address & length of the CGU registers.
+- clocks : List of phandle & clock specifiers for clocks external to the CGU.
+  Two such external clocks should be specified - first the external crystal
+  "ext" and second the RTC clock source "rtc".
+- clock-names : List of name strings for the external clocks.
+- #clock-cells: Should be 1.
+  Clock consumers specify this argument to identify a clock. The valid values
+  may be found in <dt-bindings/clock/<soctype>-cgu.h>.
+
+Example SoC include file:
+
+/ {
+	cgu: jz4740-cgu {
+		compatible = "ingenic,jz4740-cgu";
+		reg = <0x10000000 0x100>;
+		#clock-cells = <1>;
+	};
+
+	uart0: serial@10030000 {
+		clocks = <&cgu JZ4740_CLK_UART0>;
+	};
+};
+
+Example board file:
+
+/ {
+	ext: clock@0 {
+		compatible = "fixed-clock";
+		#clock-cells = <0>;
+		clock-frequency = <12000000>;
+	};
+
+	rtc: clock@1 {
+		compatible = "fixed-clock";
+		#clock-cells = <0>;
+		clock-frequency = <32768>;
+	};
+
+	&cgu {
+		clocks = <&ext> <&rtc>;
+		clock-names: "ext", "rtc";
+	};
+};