[PATCH 0/2] hwmon: (pmbus/max20860a) Add driver for Analog Devices MAX20860A

[PATCH 0/2] hwmon: (pmbus/max20860a) Add driver for Analog Devices MAX20860A

[Pradhan, Sanman]

From: Sanman Pradhan <psanman@juniper.net>

Add PMBus hwmon driver and devicetree binding for the Analog Devices
MAX20860A step-down DC-DC switching regulator.

The MAX20860A uses linear data format and provides monitoring of input
voltage, output voltage, output current, and two temperature sensors
via the PMBus interface.

During probe, write protection is configured to level 0x20 to allow
runtime access to configuration and limit registers.

Tested on Juniper Networks hardware. All sensor readings (VIN, VOUT,
IOUT, TEMP1, TEMP2) report correct values in expected ranges, status
registers function correctly, and rapid-poll stress test completes
with zero errors.

Sanman Pradhan (2):
  dt-bindings: hwmon: pmbus: Add Analog Devices MAX20860A
  hwmon: (pmbus/max20860a) Add driver for Analog Devices MAX20860A

 .../bindings/hwmon/pmbus/adi,max20860a.yaml   | 42 +++++++++++
 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 +++++++++++++++++++
 7 files changed, 191 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/pmbus/adi,max20860a.yaml
 create mode 100644 Documentation/hwmon/max20860a.rst
 create mode 100644 drivers/hwmon/pmbus/max20860a.c

-- 
2.34.1

[PATCH 1/2] dt-bindings: hwmon: pmbus: Add Analog Devices MAX20860A

[Pradhan, Sanman]

From: Sanman Pradhan <psanman@juniper.net>

Add devicetree binding documentation for the Analog Devices MAX20860A
step-down DC-DC switching regulator with PMBus interface.

Signed-off-by: Sanman Pradhan <psanman@juniper.net>
---
 .../bindings/hwmon/pmbus/adi,max20860a.yaml   | 42 +++++++++++++++++++
 1 file changed, 42 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/hwmon/pmbus/adi,max20860a.yaml

diff --git a/Documentation/devicetree/bindings/hwmon/pmbus/adi,max20860a.yaml b/Documentation/devicetree/bindings/hwmon/pmbus/adi,max20860a.yaml
new file mode 100644
index 000000000000..d864fef210b1
--- /dev/null
+++ b/Documentation/devicetree/bindings/hwmon/pmbus/adi,max20860a.yaml
@@ -0,0 +1,42 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/hwmon/pmbus/adi,max20860a.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Analog Devices MAX20860A Step-Down Converter
+
+maintainers:
+  - Sanman Pradhan <psanman@juniper.net>
+
+description: |
+  The MAX20860A is a fully integrated step-down DC-DC switching regulator
+  with PMBus interface for monitoring input/output voltage, output current
+  and temperature.
+
+  Datasheet: https://www.analog.com/en/products/max20860a.html
+
+properties:
+  compatible:
+    const: adi,max20860a
+
+  reg:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        regulator@40 {
+            compatible = "adi,max20860a";
+            reg = <0x40>;
+        };
+    };
-- 
2.34.1

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

[Pradhan, Sanman]

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

Re: [PATCH 1/2] dt-bindings: hwmon: pmbus: Add Analog Devices MAX20860A

[sashiko-bot]

> From: Sanman Pradhan <psanman@juniper.net>
> 
> Add devicetree binding documentation for the Analog Devices MAX20860A
> step-down DC-DC switching regulator with PMBus interface.
> 
> Signed-off-by: Sanman Pradhan <psanman@juniper.net>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260527045409.9092-1-sanman.pradhan@hpe.com?part=1

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

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Writing 0x20 to PMBUS_WRITE_PROTECT causes the PMBus core to lock sysfs configuration attributes as read-only.
--

commit 6a162d6f1757daa1f8dd5d77f833404928b847be
Author: Sanman Pradhan <psanman@juniper.net>

hwmon: (pmbus/max20860a) Add driver for Analog Devices MAX20860A

This commit adds a PMBus client driver for the Analog Devices MAX20860A
step-down DC-DC switching regulator. It registers the device with the PMBus
core and configures write protection during probe to enable configuration
access.

> diff --git a/drivers/hwmon/pmbus/max20860a.c b/drivers/hwmon/pmbus/max20860a.c
> new file mode 100644
> index 0000000000000..9af6888ed07e1
> --- /dev/null
> +++ b/drivers/hwmon/pmbus/max20860a.c
[ ... ]
> +/*
> + * 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 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);

[Severity: High]
Does this write to PMBUS_WRITE_PROTECT actually cause the PMBus core to lock
the sysfs configuration attributes as read-only?

The driver intentionally writes 0x20 to PMBUS_WRITE_PROTECT to allow runtime
configuration access. However, per the PMBus specification, 0x20 corresponds
to PB_WP_VOUT (BIT 5).

When pmbus_do_probe() is subsequently called, the PMBus core (in
pmbus_init_wp()) reads this register back. Seeing the 0x20 (PB_WP_VOUT) value,
the core sets the PMBUS_WRITE_PROTECTED flag in the driver's state. This
causes the PMBus core to unconditionally export all hardware monitoring limit
attributes as read-only (0444) in sysfs, which seems to defeat the intent of
enabling runtime configuration.

If 0x20 is indeed a device-specific value that enables writes, should the
driver either set PMBUS_NO_WRITE_PROTECT via platform data before calling
pmbus_do_probe(), or implement a read_byte_data hook to mask the read? Or if
the device complies with the standard PMBus specification, should 0x00 be
written instead to enable all writes?

> +}

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260527045409.9092-1-sanman.pradhan@hpe.com?part=2

Re: [PATCH 1/2] dt-bindings: hwmon: pmbus: Add Analog Devices MAX20860A

[Conor Dooley]

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On Wed, May 27, 2026 at 04:54:42AM +0000, Pradhan, Sanman wrote:
> From: Sanman Pradhan <psanman@juniper.net>
> 
> Add devicetree binding documentation for the Analog Devices MAX20860A
> step-down DC-DC switching regulator with PMBus interface.
> 
> Signed-off-by: Sanman Pradhan <psanman@juniper.net>
> ---
>  .../bindings/hwmon/pmbus/adi,max20860a.yaml   | 42 +++++++++++++++++++
>  1 file changed, 42 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/hwmon/pmbus/adi,max20860a.yaml
> 
> diff --git a/Documentation/devicetree/bindings/hwmon/pmbus/adi,max20860a.yaml b/Documentation/devicetree/bindings/hwmon/pmbus/adi,max20860a.yaml
> new file mode 100644
> index 000000000000..d864fef210b1
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/hwmon/pmbus/adi,max20860a.yaml
> @@ -0,0 +1,42 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/hwmon/pmbus/adi,max20860a.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Analog Devices MAX20860A Step-Down Converter
> +
> +maintainers:
> +  - Sanman Pradhan <psanman@juniper.net>
> +
> +description: |
> +  The MAX20860A is a fully integrated step-down DC-DC switching regulator
> +  with PMBus interface for monitoring input/output voltage, output current
> +  and temperature.
> +
> +  Datasheet: https://www.analog.com/en/products/max20860a.html
> +
> +properties:
> +  compatible:
> +    const: adi,max20860a
> +
> +  reg:
> +    maxItems: 1
> +
> +required:
> +  - compatible
> +  - reg

How come no regulator properties are permitted here?

Cheers,
Conor.

> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    i2c {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        regulator@40 {
> +            compatible = "adi,max20860a";
> +            reg = <0x40>;
> +        };
> +    };
> -- 
> 2.34.1
> 

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Re: [PATCH 1/2] dt-bindings: hwmon: pmbus: Add Analog Devices MAX20860A

[Pradhan, Sanman]

From: Sanman Pradhan <psanman@juniper.net>

Thanks Conor for the review. Will fix in v2, will add an allOf reference
to regulator.yaml and switch to unevaluatedProperties: false, will follow
the same pattern as adi,max20830.yaml, if that's ok.

Regards,
Sanman Pradhan

Re: [PATCH 1/2] dt-bindings: hwmon: pmbus: Add Analog Devices MAX20860A

[Conor Dooley]

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On Thu, May 28, 2026 at 05:06:30PM +0000, Pradhan, Sanman wrote:
> From: Sanman Pradhan <psanman@juniper.net>
> 
> Thanks Conor for the review. Will fix in v2, will add an allOf reference
> to regulator.yaml and switch to unevaluatedProperties: false, will follow
> the same pattern as adi,max20830.yaml, if that's ok.

Okay. Please don't remove quoted text when you reply, so that I don't
have to look on lore.kernel.org to figure out what it is that I am
commenting on.

Thanks,
Conor.

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Re: [PATCH 1/2] dt-bindings: hwmon: pmbus: Add Analog Devices MAX20860A

[Pradhan, Sanman]

From: Sanman Pradhan <psanman@juniper.net>

On Thu, May 28, 2026 at 18:16:25 +0100, Conor Dooley wrote:
> On Thu, May 28, 2026 at 05:06:30PM +0000, Pradhan, Sanman wrote:
> > From: Sanman Pradhan <psanman@juniper.net>
> >
> > Thanks Conor for the review. Will fix in v2, will add an allOf reference
> > to regulator.yaml and switch to unevaluatedProperties: false, will follow
> > the same pattern as adi,max20830.yaml, if that's ok.
>
> Okay. Please don't remove quoted text when you reply, so that I don't
> have to look on lore.kernel.org to figure out what it is that I am
> commenting on.

Apologies for stripping the quoted context, will make sure to
preserve it going forward.

Thank you.

Regards,
Sanman Pradhan