mfd: max597x: Add support for MAX5970 and MAX5978

Implement a regulator driver with IRQ support for fault management.
Written against documentation [1] and [2] and tested on real hardware.

Every channel has it's own regulator supply nammed 'vss1-supply' and
'vss2-supply'. The regulator supply is used to determine the output
voltage, as the smart switch provides no output regulation.
The driver requires the 'shunt-resistor-micro-ohms' to be present in
the devicetree to properly calculate current related values.

You must specify compatible devictree layout:

regulator@3a {
        reg = <0x3a>;
        vss1-supply = <&p3v3>;
        compatible = "maxim,max5978";

        ...

        regulators {
                sw0_ref: SW0 {
                        regulator-compatible = "SW0";
                        shunt-resistor-micro-ohms = <12000>;
                        ...
                }
        }
}

1: https://datasheets.maximintegrated.com/en/ds/MAX5970.pdf
2: https://datasheets.maximintegrated.com/en/ds/MAX5978.pdf

...
Changes in V12:
- Use simple_mfd_i2c driver and remove previous implementation.
- Remove newline
- Use _MFD_MAX597X_H in header file
- Successfull build need following patch from regulator:
https://lore.kernel.org/r/20230216075302.68935-1-Naresh.Solanki@9elements.com
https://lore.kernel.org/r/20230210163225.1208035-1-Naresh.Solanki@9elements.com

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Signed-off-by: Marcello Sylvester Bauer <sylv@sylv.io>
Signed-off-by: Naresh Solanki <Naresh.Solanki@9elements.com>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20230307121246.127425-2-Naresh.Solanki@9elements.com

drivers/mfd/Kconfig

@@ -266,6 +266,16 @@ config MFD_MADERA_SPI
 	  Support for the Cirrus Logic Madera platform audio SoC
 	  core functionality controlled via SPI.
 
+config MFD_MAX597X
+	tristate "Maxim 597x power switch and monitor"
+	depends on (I2C && OF)
+	select MFD_SIMPLE_MFD_I2C
+	help
+	  This driver controls a Maxim 5970/5978 switch via I2C bus.
+	  The MAX5970/5978 is a smart switch with no output regulation, but
+	  fault protection and voltage and current monitoring capabilities.
+	  Also it supports upto 4 indication leds.
+
 config MFD_CS47L15
 	bool "Cirrus Logic CS47L15"
 	select PINCTRL_CS47L15

drivers/mfd/simple-mfd-i2c.c

@@ -72,9 +72,22 @@ static const struct simple_mfd_data silergy_sy7636a = {
 	.mfd_cell_size = ARRAY_SIZE(sy7636a_cells),
 };
 
+static const struct mfd_cell max597x_cells[] = {
+	{ .name = "max597x-regulator", },
+	{ .name = "max597x-iio", },
+	{ .name = "max597x-led", },
+};
+
+static const struct simple_mfd_data maxim_max597x = {
+	.mfd_cell = max597x_cells,
+	.mfd_cell_size = ARRAY_SIZE(max597x_cells),
+};
+
 static const struct of_device_id simple_mfd_i2c_of_match[] = {
 	{ .compatible = "kontron,sl28cpld" },
 	{ .compatible = "silergy,sy7636a", .data = &silergy_sy7636a},
+	{ .compatible = "maxim,max5970", .data = &maxim_max597x},
+	{ .compatible = "maxim,max5978", .data = &maxim_max597x},
 	{}
 };
 MODULE_DEVICE_TABLE(of, simple_mfd_i2c_of_match);

include/linux/mfd/max597x.h

@@ -0,0 +1,96 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Device driver for regulators in MAX5970 and MAX5978 IC
+ *
+ * Copyright (c) 2022 9elements GmbH
+ *
+ * Author: Patrick Rudolph <patrick.rudolph@9elements.com>
+ */
+
+#ifndef _MFD_MAX597X_H
+#define _MFD_MAX597X_H
+
+#include <linux/regmap.h>
+
+#define MAX5970_NUM_SWITCHES 2
+#define MAX5978_NUM_SWITCHES 1
+#define MAX597X_NUM_LEDS     4
+
+struct max597x_data {
+	int num_switches;
+	u32 irng[MAX5970_NUM_SWITCHES];
+	u32 mon_rng[MAX5970_NUM_SWITCHES];
+	u32 shunt_micro_ohms[MAX5970_NUM_SWITCHES];
+};
+
+enum max597x_chip_type {
+	MAX597x_TYPE_MAX5978 = 1,
+	MAX597x_TYPE_MAX5970,
+};
+
+#define MAX5970_REG_CURRENT_L(ch)		(0x01 + (ch) * 4)
+#define MAX5970_REG_CURRENT_H(ch)		(0x00 + (ch) * 4)
+#define MAX5970_REG_VOLTAGE_L(ch)		(0x03 + (ch) * 4)
+#define MAX5970_REG_VOLTAGE_H(ch)		(0x02 + (ch) * 4)
+#define MAX5970_REG_MON_RANGE			0x18
+#define  MAX5970_MON_MASK			0x3
+#define  MAX5970_MON(reg, ch)			(((reg) >> ((ch) * 2)) & MAX5970_MON_MASK)
+#define  MAX5970_MON_MAX_RANGE_UV		16000000
+
+#define MAX5970_REG_CH_UV_WARN_H(ch)		(0x1A + (ch) * 10)
+#define MAX5970_REG_CH_UV_WARN_L(ch)		(0x1B + (ch) * 10)
+#define MAX5970_REG_CH_UV_CRIT_H(ch)		(0x1C + (ch) * 10)
+#define MAX5970_REG_CH_UV_CRIT_L(ch)		(0x1D + (ch) * 10)
+#define MAX5970_REG_CH_OV_WARN_H(ch)		(0x1E + (ch) * 10)
+#define MAX5970_REG_CH_OV_WARN_L(ch)		(0x1F + (ch) * 10)
+#define MAX5970_REG_CH_OV_CRIT_H(ch)		(0x20 + (ch) * 10)
+#define MAX5970_REG_CH_OV_CRIT_L(ch)		(0x21 + (ch) * 10)
+
+#define  MAX5970_VAL2REG_H(x)		(((x) >> 2) & 0xFF)
+#define  MAX5970_VAL2REG_L(x)		((x) & 0x3)
+
+#define MAX5970_REG_DAC_FAST(ch)	(0x2E + (ch))
+
+#define MAX5970_FAST2SLOW_RATIO		200
+
+#define MAX5970_REG_STATUS0		0x31
+#define  MAX5970_CB_IFAULTF(ch)		(1 << (ch))
+#define  MAX5970_CB_IFAULTS(ch)		(1 << ((ch) + 4))
+
+#define MAX5970_REG_STATUS1		0x32
+#define  STATUS1_PROT_MASK		0x3
+#define  STATUS1_PROT(reg) \
+	(((reg) >> 6) & STATUS1_PROT_MASK)
+#define  STATUS1_PROT_SHUTDOWN		0
+#define  STATUS1_PROT_CLEAR_PG		1
+#define  STATUS1_PROT_ALERT_ONLY	2
+
+#define MAX5970_REG_STATUS2		0x33
+#define  MAX5970_IRNG_MASK		0x3
+#define  MAX5970_IRNG(reg, ch) \
+	(((reg) >> ((ch) * 2)) & MAX5970_IRNG_MASK)
+
+#define MAX5970_REG_STATUS3		0x34
+#define  MAX5970_STATUS3_ALERT		BIT(4)
+#define  MAX5970_STATUS3_PG(ch)		BIT(ch)
+
+#define MAX5970_REG_FAULT0		0x35
+#define  UV_STATUS_WARN(ch)		(1 << (ch))
+#define  UV_STATUS_CRIT(ch)		(1 << ((ch) + 4))
+
+#define MAX5970_REG_FAULT1		0x36
+#define  OV_STATUS_WARN(ch)		(1 << (ch))
+#define  OV_STATUS_CRIT(ch)		(1 << ((ch) + 4))
+
+#define MAX5970_REG_FAULT2		0x37
+#define  OC_STATUS_WARN(ch)		(1 << (ch))
+
+#define MAX5970_REG_CHXEN		0x3b
+#define  CHXEN(ch)			(3 << ((ch) * 2))
+
+#define MAX5970_REG_LED_FLASH		0x43
+
+#define MAX_REGISTERS			0x49
+#define ADC_MASK			0x3FF
+
+#endif				/* _MFD_MAX597X_H */