linux-kernel - [PATCH v3 2/3] dt-bindings: clk: add documentation for the SiFive PRCI driver

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Message-Id: <20190411082733.3736-3-paul.walmsley@sifive.com>
Date:   Thu, 11 Apr 2019 01:27:34 -0700
From:   Paul Walmsley <paul.walmsley@...ive.com>
To:     linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-clk@...r.kernel.org, devicetree@...r.kernel.org
Cc:     Paul Walmsley <paul.walmsley@...ive.com>,
        Paul Walmsley <paul@...an.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Palmer Dabbelt <palmer@...ive.com>,
        Megan Wachs <megan@...ive.com>
Subject: [PATCH v3 2/3] dt-bindings: clk: add documentation for the SiFive PRCI driver

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

This version includes changes requested by Stephen Boyd
<sboyd@...nel.org> and Rob Herring <robh@...nel.org>, and
fixes some errors in the initial version.

Signed-off-by: Paul Walmsley <paul.walmsley@...ive.com>
Signed-off-by: Paul Walmsley <paul@...an.com>
Cc: Michael Turquette <mturquette@...libre.com>
Cc: Stephen Boyd <sboyd@...nel.org>
Cc: Rob Herring <robh+dt@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Palmer Dabbelt <palmer@...ive.com>
Cc: Megan Wachs <megan@...ive.com>
Cc: linux-clk@...r.kernel.org
Cc: devicetree@...r.kernel.org
Cc: linux-riscv@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org
---
 .../bindings/clock/sifive/fu540-prci.txt      | 46 +++++++++++++++++++
 1 file changed, 46 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..349808f4fb8c
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/sifive/fu540-prci.txt
@@ -0,0 +1,46 @@
+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".  Only one value is
+	supported: "sifive,fu540-c000-prci"
+- 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/dt-bindings/clock/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.  These nodes should be present
+underneath /, rather than /soc.
+
+Examples:
+
+/* under /, in PCB-specific DT data */
+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";
+};
+
+/* under /soc, in SoC-specific DT data */
+prci: clock-controller@...00000 {
+	compatible = "sifive,fu540-c000-prci";
+	reg = <0x0 0x10000000 0x0 0x1000>;
+	clocks = <&hfclk>, <&rtcclk>;
+	#clock-cells = <1>;
+};
-- 
2.20.1