Message-Id: <20190507140413.28335-1-mike.looijmans@topic.nl>
Date:   Tue,  7 May 2019 16:04:13 +0200
From:   Mike Looijmans <mike.looijmans@...ic.nl>
To:     devicetree@...r.kernel.org, linux-clk@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, mturquette@...libre.com,
        sboyd@...nel.org, robh+dt@...nel.org, mark.rutland@....com,
        Mike Looijmans <mike.looijmans@...ic.nl>
Subject: [PATCH v2] dt-bindings: clock: Add silabs,si5341

Adds the devicetree bindings for the Si5341 and Si5340 chips from
Silicon Labs. These are multiple-input multiple-output clock
synthesizers.

Signed-off-by: Mike Looijmans <mike.looijmans@...ic.nl>
---
v2: Add data sheet reference.
    Restructured to enable use of "assigned-clock*" properties to set
    up both outputs and internal synthesizers.
    Nicer indentation.
    Updated subject line and body of commit message.
    If these bindings are (mostly) acceptable, I'll post an updated
    driver patch v2 to implement these changes.

 .../bindings/clock/silabs,si5341.txt          | 187 ++++++++++++++++++
 1 file changed, 187 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/clock/silabs,si5341.txt

diff --git a/Documentation/devicetree/bindings/clock/silabs,si5341.txt b/Documentation/devicetree/bindings/clock/silabs,si5341.txt
new file mode 100644
index 000000000000..6086dfcaeecf
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/silabs,si5341.txt
@@ -0,0 +1,187 @@
+Binding for Silicon Labs Si5341 and Si5340 programmable i2c clock generator.
+
+Reference
+[1] Si5341 Data Sheet
+    https://www.silabs.com/documents/public/data-sheets/Si5341-40-D-DataSheet.pdf
+[2] Si5341 Reference Manual
+    https://www.silabs.com/documents/public/reference-manuals/Si5341-40-D-RM.pdf
+
+The Si5341 and Si5340 are programmable i2c clock generators with up to 10 output
+clocks. The chip contains a PLL that sources 5 (or 4) multisynth clocks, which
+in turn can be directed to any of the 10 (or 4) outputs through a divider.
+The internal structure of the clock generators can be found in [2].
+
+The driver can be used in "as is" mode, reading the current settings from the
+chip at boot, in case you have a (pre-)programmed device. If the PLL is not
+configured when the driver probes, it assumes the driver must fully initialize
+it.
+
+The device type, speed grade and revision are determined runtime by probing.
+
+The driver currently only supports XTAL input mode, and does not support any
+fancy input configurations. They can still be programmed into the chip and
+the driver will leave them "as is".
+
+==I2C device node==
+
+Required properties:
+- compatible: shall be one of the following:
+	"silabs,si5340" - Si5340 A/B/C/D
+	"silabs,si5341" - Si5341 A/B/C/D
+- reg: i2c device address, usually 0x74
+- #clock-cells: from common clock binding; shall be set to 2.
+	The first value is "0" for outputs, "1" for synthesizers.
+	The second value is the output or synthesizer index.
+- clocks: from common clock binding; list of parent clock  handles,
+	corresponding to inputs. Use a fixed clock for the "xtal" input.
+	At least one must be present.
+- clock-names: One of: "xtal", "in0", "in1", "in2"
+- vdd-supply: Regulator node for VDD
+
+Optional properties:
+- vdda-supply: Regulator node for VDDA
+- vdds-supply: Regulator node for VDDS
+- silabs,pll-m-num, silabs,pll-m-den: Numerator and denominator for PLL
+  feedback divider. Must be such that the PLL output is in the valid range. For
+  example, to create 14GHz from a 48MHz xtal, use m-num=14000 and m-den=48. Only
+  the fraction matters, using 3500 and 12 will deliver the exact same result.
+  If these are not specified, and the PLL is not yet programmed when the driver
+  probes, the PLL will be set to 14GHz.
+- silabs,reprogram: When present, the driver will always assume the device must
+  be initialized, and always performs the soft-reset routine. Since this will
+  temporarily stop all output clocks, don't do this if the chip is generating
+  the CPU clock for example.
+- interrupts: Interrupt for INTRb pin.
+
+== Child nodes: Synthesizers ==
+
+In order to refer to the internal synthesizers, there can be a child node named
+"synthesizers".
+
+Required synthesizers node properties:
+- #address-cells: shall be set to 1.
+- #size-cells: shall be set to 0.
+
+Each child of this node corresponds to a multisynth in the Si534X chip. This
+allows the synthesizer to be referred to with assigned-clocks.
+
+Required child node properties:
+- reg: synthesizer index in range 0..4 for Si5341 and 0..3 for Si5340.
+
+== Child nodes: Outputs ==
+
+The child node "outputs" lists the output clocks.
+
+Required outputs node properties:
+- #address-cells: shall be set to 1.
+- #size-cells: shall be set to 0.
+
+Each of the clock outputs can be overwritten individually by
+using a child node to the outputs child node. If a child node for a clock
+output is not set, the configuration remains unchanged.
+
+Required child node properties:
+- reg: number of clock output.
+
+Optional child node properties:
+- vdd-supply: Regulator node for VDD for this output. The driver selects default
+	values for common-mode and amplitude based on the voltage.
+- silabs,format: Output format, one of:
+	1 = differential (defaults to LVDS levels)
+	2 = low-power (defaults to HCSL levels)
+	4 = LVCMOS
+- silabs,common-mode: Manually overide output common mode, see [2] for values
+- silabs,amplitude: Manually override output amplitude, see [2] for values
+- silabs,synth-master: boolean. If present, this output is allowed to change the
+	multisynth frequency dynamically.
+- silabs,disable-state : clock output disable state, shall be
+	0 = clock output is driven LOW when disabled
+	1 = clock output is driven HIGH when disabled
+
+==Example==
+
+/* 48MHz reference crystal */
+ref48: ref48M {
+	compatible = "fixed-clock";
+	#clock-cells = <0>;
+	clock-frequency = <48000000>;
+};
+
+i2c-master-node {
+	/* Programmable clock (for logic) */
+	si5341: clock-generator@74 {
+		reg = <0x74>;
+		compatible = "silabs,si5341";
+		#clock-cells = <2>;
+		#address-cells = <1>;
+		#size-cells = <0>;
+		clocks = <&ref48>;
+		clock-names = "xtal";
+
+		silabs,pll-m-num = <14000>; /* PLL at 14.0 GHz */
+		silabs,pll-m-den = <48>;
+		silabs,reprogram; /* Chips are not programmed, always reset */
+
+		synthesizers {
+			synth@2 {
+				reg = <2>;
+			};
+		};
+
+		outputs {
+			out@0 {
+				reg = <0>;
+				silabs,format = <1>; /* LVDS 3v3 */
+				silabs,common-mode = <3>;
+				silabs,amplitude = <3>;
+				silabs,synth-master;
+			};
+
+			/*
+			 * Output 6 configuration:
+			 *  LVDS 1v8
+			 */
+			out@6 {
+				reg = <6>;
+				silabs,format = <1>; /* LVDS 1v8 */
+				silabs,common-mode = <13>;
+				silabs,amplitude = <3>;
+			};
+
+			/*
+			 * Output 8 configuration:
+			 *  HCSL 3v3
+			 */
+			out@8 {
+				reg = <8>;
+				silabs,format = <2>;
+				silabs,common-mode = <11>;
+				silabs,amplitude = <3>;
+			};
+		};
+	};
+};
+
+some-video-node {
+	/* Standard clock bindings */
+	clock-names = "pixel";
+	clocks = <&si5341 0 7>; /* Output 7 */
+
+	/* Set output 7 to use syntesizer 3 as its parent */
+	assigned-clocks = <&si5341 0 7>, <&si5341 1 3>;
+	assigned-clock-parents = <&si5341 1 3>;
+	/* Set output 7 to 148.5 MHz using a synth frequency of 594 MHz */
+	assigned-clock-rates = <148500000>, <594000000>;
+};
+
+some-audio-node {
+	clock-names = "i2s-clk";
+	clocks = <&si5341 0 0>;
+	/*
+	 * since output 0 is a synth-master, the synth will be automatically set
+	 * to an appropriate frequency when the audio driver requests another
+	 * frequency. We give control over synth 2 to this output here.
+	 */
+	assigned-clocks = <&si5341 0 0>;
+	assigned-clock-parents = <&si5341 1 2>;
+};
-- 
2.17.1

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