mfd: Add device-tree binding doc for PMIC MAX77620/MAX20024

The MAXIM PMIC MAX77620 and MAX20024 are power management IC
which supports RTC, GPIO, DCDC/LDO regulators, interrupt,
watchdog etc.

Add DT binding document for the different functionality of
this device.
Signed-off-by: NLaxman Dewangan <ldewangan@nvidia.com>
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NLee Jones <lee.jones@linaro.org>

Documentation/devicetree/bindings/mfd/max77620.txt

+MAX77620 Power management IC from Maxim Semiconductor.
+
+Required properties:
+-------------------
+- compatible: Must be one of
+		"maxim,max77620"
+		"maxim,max20024".
+- reg: I2C device address.
+
+Optional properties:
+-------------------
+- interrupts:		The interrupt on the parent the controller is
+			connected to.
+- interrupt-controller: Marks the device node as an interrupt controller.
+- #interrupt-cells:	is <2> and their usage is compliant to the 2 cells
+			variant of <../interrupt-controller/interrupts.txt>
+			IRQ numbers for different interrupt source of MAX77620
+			are defined at dt-bindings/mfd/max77620.h.
+
+Optional subnodes and their properties:
+=======================================
+
+Flexible power sequence configurations:
+--------------------------------------
+The Flexible Power Sequencer (FPS) allows each regulator to power up under
+hardware or software control. Additionally, each regulator can power on
+independently or among a group of other regulators with an adjustable power-up
+and power-down delays (sequencing). GPIO1, GPIO2, and GPIO3 can be programmed
+to be part of a sequence allowing external regulators to be sequenced along
+with internal regulators. 32KHz clock can be programmed to be part of a
+sequence.
+
+The flexible sequencing structure consists of two hardware enable inputs
+(EN0, EN1), and 3 master sequencing timers called FPS0, FPS1 and FPS2.
+Each master sequencing timer is programmable through its configuration
+register to have a hardware enable source (EN1 or EN2) or a software enable
+source (SW). When enabled/disabled, the master sequencing timer generates
+eight sequencing events on different time periods called slots. The time
+period between each event is programmable within the configuration register.
+Each regulator, GPIO1, GPIO2, GPIO3, and 32KHz clock has a flexible power
+sequence slave register which allows its enable source to be specified as
+a flexible power sequencer timer or a software bit. When a FPS source of
+regulators, GPIOs and clocks specifies the enable source to be a flexible
+power sequencer, the power up and power down delays can be specified in
+the regulators, GPIOs and clocks flexible power sequencer configuration
+registers.
+
+When FPS event cleared (set to LOW), regulators, GPIOs and 32KHz
+clock are set into following state at the sequencing event that
+corresponds to its flexible sequencer configuration register.
+	Sleep state: 			In this state, regulators, GPIOs
+					and 32KHz clock get disabled at
+					the sequencing event.
+	Global Low Power Mode (GLPM):	In this state, regulators are set in
+					low power mode at the sequencing event.
+
+The configuration parameters of FPS is provided through sub-node "fps"
+and their child for FPS specific. The child node name for FPS are "fps0",
+"fps1", and "fps2" for FPS0, FPS1 and FPS2 respectively.
+
+The FPS configurations like FPS source, power up and power down slots for
+regulators, GPIOs and 32kHz clocks are provided in their respective
+configuration nodes which is explained in respective sub-system DT
+binding document.
+
+There is need for different FPS configuration parameters based on system
+state like when system state changed from active to suspend or active to
+power off (shutdown).
+
+Optional properties:
+-------------------
+-maxim,fps-event-source:		u32, FPS event source like external
+					hardware input to PMIC i.e. EN0, EN1 or
+					software (SW).
+					The macros are defined on
+						dt-bindings/mfd/max77620.h
+					for different control source.
+					- MAX77620_FPS_EVENT_SRC_EN0
+						for hardware input pin EN0.
+					- MAX77620_FPS_EVENT_SRC_EN1
+						for hardware input pin EN1.
+					- MAX77620_FPS_EVENT_SRC_SW
+						for software control.
+
+-maxim,shutdown-fps-time-period-us:	u32, FPS time period in microseconds
+					when system enters in to shutdown
+					state.
+
+-maxim,suspend-fps-time-period-us:	u32, FPS time period in microseconds
+					when system enters in to suspend state.
+
+-maxim,device-state-on-disabled-event:	u32, describe the PMIC state when FPS
+					event cleared (set to LOW) whether it
+					should go to sleep state or low-power
+					state. Following are valid values:
+					- MAX77620_FPS_INACTIVE_STATE_SLEEP
+						to set the PMIC state to sleep.
+					- MAX77620_FPS_INACTIVE_STATE_LOW_POWER
+						to set the PMIC state to low
+						power.
+					Absence of this property or other value
+					will not change device state when FPS
+					event get cleared.
+
+Here supported time periods by device in microseconds are as follows:
+MAX77620 supports 40, 80, 160, 320, 640, 1280, 2560 and 5120 microseconds.
+MAX20024 supports 20, 40, 80, 160, 320, 640, 1280 and 2540 microseconds.
+
+For DT binding details of different sub modules like GPIO, pincontrol,
+regulator, power, please refer respective device-tree binding document
+under their respective sub-system directories.
+
+Example:
+--------
+#include <dt-bindings/mfd/max77620.h>
+
+max77620@3c {
+	compatible = "maxim,max77620";
+	reg = <0x3c>;
+
+	interrupt-parent = <&intc>;
+	interrupts = <0 86 IRQ_TYPE_NONE>;
+
+	interrupt-controller;
+	#interrupt-cells = <2>;
+
+	fps {
+		fps0 {
+			maxim,shutdown-fps-time-period-us = <1280>;
+			maxim,fps-event-source = <MAX77620_FPS_EVENT_SRC_EN1>;
+		};
+
+		fps1 {
+			maxim,shutdown-fps-time-period-us = <1280>;
+			maxim,fps-event-source = <MAX77620_FPS_EVENT_SRC_EN0>;
+		};
+
+		fps2 {
+			maxim,shutdown-fps-time-period-us = <1280>;
+			maxim,fps-event-source = <MAX77620_FPS_EVENT_SRC_SW>;
+		};
+	};
+};

include/dt-bindings/mfd/max77620.h

+/*
+ * This header provides macros for MAXIM MAX77620 device bindings.
+ *
+ * Copyright (c) 2016, NVIDIA Corporation.
+ * Author: Laxman Dewangan <ldewangan@nvidia.com>
+ */
+
+#ifndef _DT_BINDINGS_MFD_MAX77620_H
+#define _DT_BINDINGS_MFD_MAX77620_H
+
+/* MAX77620 interrupts */
+#define MAX77620_IRQ_TOP_GLBL		0 /* Low-Battery */
+#define MAX77620_IRQ_TOP_SD		1 /* SD power fail */
+#define MAX77620_IRQ_TOP_LDO		2 /* LDO power fail */
+#define MAX77620_IRQ_TOP_GPIO		3 /* GPIO internal int to MAX77620 */
+#define MAX77620_IRQ_TOP_RTC		4 /* RTC */
+#define MAX77620_IRQ_TOP_32K		5 /* 32kHz oscillator */
+#define MAX77620_IRQ_TOP_ONOFF		6 /* ON/OFF oscillator */
+#define MAX77620_IRQ_LBT_MBATLOW	7 /* Thermal alarm status, > 120C */
+#define MAX77620_IRQ_LBT_TJALRM1	8 /* Thermal alarm status, > 120C */
+#define MAX77620_IRQ_LBT_TJALRM2	9 /* Thermal alarm status, > 140C */
+
+/* FPS event source */
+#define MAX77620_FPS_EVENT_SRC_EN0		0
+#define MAX77620_FPS_EVENT_SRC_EN1		1
+#define MAX77620_FPS_EVENT_SRC_SW		2
+
+/* Device state when FPS event LOW  */
+#define MAX77620_FPS_INACTIVE_STATE_SLEEP	0
+#define MAX77620_FPS_INACTIVE_STATE_LOW_POWER	1
+
+/* FPS source */
+#define MAX77620_FPS_SRC_0			0
+#define MAX77620_FPS_SRC_1			1
+#define MAX77620_FPS_SRC_2			2
+#define MAX77620_FPS_SRC_NONE			3
+#define MAX77620_FPS_SRC_DEF			4
+
+#endif