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

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index fcc141e067b9..d381d0e63455 100644
--- a/drivers/mfd/Kconfig
+++ b/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