[PATCH v2 2/3] dt-bindings: clk: add documentation for the SiFive PRCI driver

[Paul Walmsley <paul.walmsley@sifive.com>]

Add DT binding documentation for the Linux driver for the SiFive
PRCI clock & reset control IP block, as found on the SiFive
FU540 chip.

Cc: Michael Turquette <mturquette@baylibre.com>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Megan Wachs <megan@sifive.com>
Cc: linux-clk@vger.kernel.org
Cc: devicetree@vger.kernel.org
Cc: linux-riscv@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>
---
v2: remove out-of-date example, add documentation for the compatible
    string and for the required PCB clock nodes

.../bindings/clock/sifive/fu540-prci.txt      | 43 +++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/clock/sifive/fu540-prci.txt

diff --git a/Documentation/devicetree/bindings/clock/sifive/fu540-prci.txt b/Documentation/devicetree/bindings/clock/sifive/fu540-prci.txt
new file mode 100644
index 000000000000..d7c1e83fa5ed
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/sifive/fu540-prci.txt
@@ -0,0 +1,43 @@
+SiFive FU540 PRCI bindings
+
+On the FU540 family of SoCs, most system-wide clock and reset integration
+is via the PRCI IP block.
+
+Required properties:
+- compatible: Should be "sifive,<chip>-prci<version>".  As of the time this
+              file was written, only one value is supported:
+	      "sifive,fu540-c000-prci0"
+- reg: Should describe the PRCI's register target physical address region
+- clocks: Should point to the hfclk device tree node and the rtcclk
+          device tree node.  The RTC clock here is not a time-of-day clock,
+	  but is instead a high-stability clock source for system timers
+	  and cycle counters.
+- #clock-cells: Should be <1>
+
+The clock consumer should specify the desired clock via the clock ID
+macros defined in include/linux/clk/sifive-fu540-prci.h.  These macros
+begin with PRCI_CLK_.
+
+The hfclk and rtcclk nodes are required, and represent physical
+crystals or resonators located on the PCB.
+
+Examples:
+
+hfclk: hfclk {
+	#clock-cells = <0>;
+	compatible = "fixed-clock";
+	clock-frequency = <33333333>;
+	clock-output-names = "hfclk";
+};
+rtcclk: rtcclk {
+	#clock-cells = <0>;
+	compatible = "fixed-clock";
+	clock-frequency = <1000000>;
+	clock-output-names = "rtcclk";
+};
+prci0: prci@10000000 {
+	compatible = "sifive,fu540-c000-prci0";
+	reg = <0x0 0x10000000 0x0 0x1000>;
+	clocks = <&hfclk>, <&rtcclk>;
+	#clock-cells = <1>;
+};
-- 
2.19.1