[PATCH 2/2] hwmon: (pmbus/max20860a) Add driver for Analog Devices MAX20860A

["Pradhan, Sanman" <sanman.pradhan@hpe.com>]

From: Sanman Pradhan <psanman@juniper.net>

Add a PMBus driver for the Analog Devices MAX20860A step-down DC-DC
switching regulator. The MAX20860A provides monitoring of input/output
voltage, output current, and temperature via the PMBus interface using
linear data format.

During probe, write protection is configured to level 0x20 (all writes
enabled except WRITE_PROTECT itself) to allow runtime configuration
access.

Signed-off-by: Sanman Pradhan <psanman@juniper.net>
---
 Documentation/hwmon/index.rst     |  1 +
 Documentation/hwmon/max20860a.rst | 60 ++++++++++++++++++++++++++
 MAINTAINERS                       |  8 ++++
 drivers/hwmon/pmbus/Kconfig       |  9 ++++
 drivers/hwmon/pmbus/Makefile      |  1 +
 drivers/hwmon/pmbus/max20860a.c   | 70 +++++++++++++++++++++++++++++++
 6 files changed, 149 insertions(+)
 create mode 100644 Documentation/hwmon/max20860a.rst
 create mode 100644 drivers/hwmon/pmbus/max20860a.c

diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
index e880c6ca84f0..ffaacda416e7 100644
--- a/Documentation/hwmon/index.rst
+++ b/Documentation/hwmon/index.rst
@@ -163,6 +163,7 @@ Hardware Monitoring Kernel Drivers
    max20730
    max20751
    max20830
+   max20860a
    max31722
    max31730
    max31760
diff --git a/Documentation/hwmon/max20860a.rst b/Documentation/hwmon/max20860a.rst
new file mode 100644
index 000000000000..d9bf2ef90734
--- /dev/null
+++ b/Documentation/hwmon/max20860a.rst
@@ -0,0 +1,60 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Kernel driver max20860a
+=======================
+
+Supported chips:
+
+  * Analog Devices MAX20860A
+
+    Prefix: 'max20860a'
+
+    Addresses scanned: -
+
+    Datasheet: https://www.analog.com/en/products/max20860a.html
+
+Author:
+
+  - Sanman Pradhan <psanman@juniper.net>
+
+
+Description
+-----------
+
+This driver supports hardware monitoring for Analog Devices MAX20860A
+Step-Down Switching Regulator with PMBus Interface.
+
+The MAX20860A is a fully integrated step-down DC-DC switching regulator.
+Through the PMBus interface, the device can monitor input/output voltages,
+output current and temperature.
+
+The driver is a client driver to the core PMBus driver. Please see
+Documentation/hwmon/pmbus.rst for details on PMBus client drivers.
+
+Usage Notes
+-----------
+
+This driver does not auto-detect devices. You will have to instantiate
+the devices explicitly.
+
+The driver clears write protection (sets WRITE_PROTECT to 0x20) during
+probe to allow configuration access while keeping the WRITE_PROTECT
+command itself protected.
+
+Sysfs entries
+-------------
+
+================= ========================================
+in1_label         "vin"
+in1_input         Measured input voltage
+in1_alarm         Input voltage alarm
+in2_label         "vout1"
+in2_input         Measured output voltage
+in2_alarm         Output voltage alarm
+curr1_label       "iout1"
+curr1_input       Measured output current
+curr1_alarm       Output current alarm
+temp1_input       Measured temperature
+temp1_alarm       Chip temperature alarm
+temp2_input       Measured temperature (secondary)
+================= ========================================
diff --git a/MAINTAINERS b/MAINTAINERS
index b71acb130395..1d9651947ee3 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15688,6 +15688,14 @@ F:	Documentation/devicetree/bindings/hwmon/pmbus/adi,max20830.yaml
 F:	Documentation/hwmon/max20830.rst
 F:	drivers/hwmon/pmbus/max20830.c
 
+MAX20860A HARDWARE MONITOR DRIVER
+M:	Sanman Pradhan <psanman@juniper.net>
+L:	linux-hwmon@vger.kernel.org
+S:	Maintained
+F:	Documentation/devicetree/bindings/hwmon/pmbus/adi,max20860a.yaml
+F:	Documentation/hwmon/max20860a.rst
+F:	drivers/hwmon/pmbus/max20860a.c
+
 MAX2175 SDR TUNER DRIVER
 M:	Ramesh Shanmugasundaram <rashanmu@gmail.com>
 L:	linux-media@vger.kernel.org
diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
index 64f38654f4e7..5825dda75f2c 100644
--- a/drivers/hwmon/pmbus/Kconfig
+++ b/drivers/hwmon/pmbus/Kconfig
@@ -402,6 +402,15 @@ config SENSORS_MAX20830
 	  This driver can also be built as a module. If so, the module will
 	  be called max20830.
 
+config SENSORS_MAX20860A
+	tristate "Analog Devices MAX20860A"
+	help
+	  If you say yes here you get hardware monitoring support for Analog
+	  Devices MAX20860A step-down converter.
+
+	  This driver can also be built as a module. If so, the module will
+	  be called max20860a.
+
 config SENSORS_MAX31785
 	tristate "Maxim MAX31785 and compatibles"
 	help
diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
index 1f2c73b71953..ffc05f493213 100644
--- a/drivers/hwmon/pmbus/Makefile
+++ b/drivers/hwmon/pmbus/Makefile
@@ -39,6 +39,7 @@ obj-$(CONFIG_SENSORS_MAX17616)	+= max17616.o
 obj-$(CONFIG_SENSORS_MAX20730)	+= max20730.o
 obj-$(CONFIG_SENSORS_MAX20751)	+= max20751.o
 obj-$(CONFIG_SENSORS_MAX20830)	+= max20830.o
+obj-$(CONFIG_SENSORS_MAX20860A)	+= max20860a.o
 obj-$(CONFIG_SENSORS_MAX31785)	+= max31785.o
 obj-$(CONFIG_SENSORS_MAX34440)	+= max34440.o
 obj-$(CONFIG_SENSORS_MAX8688)	+= max8688.o
diff --git a/drivers/hwmon/pmbus/max20860a.c b/drivers/hwmon/pmbus/max20860a.c
new file mode 100644
index 000000000000..9af6888ed07e
--- /dev/null
+++ b/drivers/hwmon/pmbus/max20860a.c
@@ -0,0 +1,70 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Hardware monitoring driver for Analog Devices MAX20860A
+ *
+ * SPDX-FileCopyrightText: Copyright Hewlett Packard Enterprise Development LP
+ */
+
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include "pmbus.h"
+
+/*
+ * Writing 0x20 to WRITE_PROTECT disables all write protection except
+ * for the WRITE_PROTECT command itself, enabling configuration access.
+ */
+#define MAX20860A_WRITE_ENABLE	0x20
+
+static struct pmbus_driver_info max20860a_info = {
+	.pages = 1,
+	.format[PSC_VOLTAGE_IN] = linear,
+	.format[PSC_VOLTAGE_OUT] = linear,
+	.format[PSC_CURRENT_OUT] = linear,
+	.format[PSC_TEMPERATURE] = linear,
+	.func[0] = PMBUS_HAVE_VIN | PMBUS_HAVE_VOUT |
+		PMBUS_HAVE_STATUS_VOUT |
+		PMBUS_HAVE_IOUT | PMBUS_HAVE_STATUS_IOUT |
+		PMBUS_HAVE_TEMP | PMBUS_HAVE_TEMP2 |
+		PMBUS_HAVE_STATUS_TEMP | PMBUS_HAVE_STATUS_INPUT,
+};
+
+static int max20860a_probe(struct i2c_client *client)
+{
+	int ret;
+
+	ret = i2c_smbus_write_byte_data(client, PMBUS_WRITE_PROTECT,
+					MAX20860A_WRITE_ENABLE);
+	if (ret < 0)
+		return dev_err_probe(&client->dev, ret,
+				     "failed to configure write protection\n");
+
+	return pmbus_do_probe(client, &max20860a_info);
+}
+
+static const struct i2c_device_id max20860a_id[] = {
+	{"max20860a"},
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, max20860a_id);
+
+static const struct of_device_id max20860a_of_match[] = {
+	{ .compatible = "adi,max20860a" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, max20860a_of_match);
+
+static struct i2c_driver max20860a_driver = {
+	.driver = {
+		.name = "max20860a",
+		.of_match_table = max20860a_of_match,
+	},
+	.probe = max20860a_probe,
+	.id_table = max20860a_id,
+};
+
+module_i2c_driver(max20860a_driver);
+
+MODULE_AUTHOR("Sanman Pradhan <psanman@juniper.net>");
+MODULE_DESCRIPTION("PMBus driver for Analog Devices MAX20860A");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS("PMBUS");
-- 
2.34.1