[PATCH v4 2/2] hwmon: Add driver for MPS MPQ8785 Synchronous Step-Down Converter

[Charles Hsu <ythsu0511@gmail.com>]

Add support for mpq8785 device from Monolithic Power Systems, Inc.
(MPS) vendor. This is synchronous step-down controller.

Signed-off-by: Charles Hsu <ythsu0511@gmail.com>

---
Change in v1:
    Initial patchset.
Change in v2:
    1.Add pmbus support status registers.
    2.Add mpq8785 in trivial-devices.yaml.
    3.Remove format[PSC_VOLTAGE_OUT].
    4.Fix MODULE_DESCRIPTION.
Change in v3:
    1.Identify vout_mode.
    2.Separate dt-binding.
Change in v4:
    1.Return an error if reading VOUT_MODE fails.
---
 Documentation/hwmon/index.rst   |  1 +
 Documentation/hwmon/mpq8785.rst | 94 +++++++++++++++++++++++++++++++++
 drivers/hwmon/pmbus/Kconfig     |  9 ++++
 drivers/hwmon/pmbus/Makefile    |  1 +
 drivers/hwmon/pmbus/mpq8785.c   | 89 +++++++++++++++++++++++++++++++
 5 files changed, 194 insertions(+)
 create mode 100644 Documentation/hwmon/mpq8785.rst
 create mode 100644 drivers/hwmon/pmbus/mpq8785.c

diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
index c7ed1f73ac06..085ad6ca9b05 100644
--- a/Documentation/hwmon/index.rst
+++ b/Documentation/hwmon/index.rst
@@ -163,6 +163,7 @@ Hardware Monitoring Kernel Drivers
    mp2975
    mp5023
    mp5990
+   mpq8785
    nct6683
    nct6775
    nct7802
diff --git a/Documentation/hwmon/mpq8785.rst b/Documentation/hwmon/mpq8785.rst
new file mode 100644
index 000000000000..bf8176b87086
--- /dev/null
+++ b/Documentation/hwmon/mpq8785.rst
@@ -0,0 +1,94 @@
+.. SPDX-License-Identifier: GPL-2.0-only
+
+Kernel driver mpq8785
+=======================
+
+Supported chips:
+
+  * MPS MPQ8785
+
+    Prefix: 'mpq8785'
+
+Author: Charles Hsu <ythsu0511@gmail.com>
+
+Description
+-----------
+
+The MPQ8785 is a fully integrated, PMBus-compatible, high-frequency, synchronous
+buck converter. The MPQ8785 offers a very compact solution that achieves up to
+40A output current per phase, with excellent load and line regulation over a
+wide input supply range. The MPQ8785 operates at high efficiency over a wide
+output current load range.
+
+The PMBus interface provides converter configurations and key parameters
+monitoring.
+
+The MPQ8785 adopts MPS's proprietary multi-phase digital constant-on-time (MCOT)
+control, which provides fast transient response and eases loop stabilization.
+The MCOT scheme also allows multiple MPQ8785 devices to be connected in parallel
+with excellent current sharing and phase interleaving for high-current
+applications.
+
+Fully integrated protection features include over-current protection (OCP),
+over-voltage protection (OVP), under-voltage protection (UVP), and
+over-temperature protection (OTP).
+
+The MPQ8785 requires a minimal number of readily available, standard external
+components, and is available in a TLGA (5mmx6mm) package.
+
+Device compliant with:
+
+- PMBus rev 1.3 interface.
+
+The driver exports the following attributes via the 'sysfs' files
+for input voltage:
+
+**in1_input**
+
+**in1_label**
+
+**in1_max**
+
+**in1_max_alarm**
+
+**in1_min**
+
+**in1_min_alarm**
+
+**in1_crit**
+
+**in1_crit_alarm**
+
+The driver provides the following attributes for output voltage:
+
+**in2_input**
+
+**in2_label**
+
+**in2_alarm**
+
+The driver provides the following attributes for output current:
+
+**curr1_input**
+
+**curr1_label**
+
+**curr1_max**
+
+**curr1_max_alarm**
+
+**curr1_crit**
+
+**curr1_crit_alarm**
+
+The driver provides the following attributes for temperature:
+
+**temp1_input**
+
+**temp1_max**
+
+**temp1_max_alarm**
+
+**temp1_crit**
+
+**temp1_crit_alarm**
diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
index 294808f5240a..557ae0c414b0 100644
--- a/drivers/hwmon/pmbus/Kconfig
+++ b/drivers/hwmon/pmbus/Kconfig
@@ -377,6 +377,15 @@ config SENSORS_MPQ7932
 	  This driver can also be built as a module. If so, the module will
 	  be called mpq7932.
 
+config SENSORS_MPQ8785
+	tristate "MPS MPQ8785"
+	help
+	  If you say yes here you get hardware monitoring functionality support
+	  for power management IC MPS MPQ8785.
+
+	  This driver can also be built as a module. If so, the module will
+	  be called mpq8785.
+
 config SENSORS_PIM4328
 	tristate "Flex PIM4328 and compatibles"
 	help
diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
index cf8a76744545..f14ecf03ad77 100644
--- a/drivers/hwmon/pmbus/Makefile
+++ b/drivers/hwmon/pmbus/Makefile
@@ -39,6 +39,7 @@ obj-$(CONFIG_SENSORS_MP2975)	+= mp2975.o
 obj-$(CONFIG_SENSORS_MP5023)	+= mp5023.o
 obj-$(CONFIG_SENSORS_MP5990)	+= mp5990.o
 obj-$(CONFIG_SENSORS_MPQ7932)	+= mpq7932.o
+obj-$(CONFIG_SENSORS_MPQ8785)	+= mpq8785.o
 obj-$(CONFIG_SENSORS_PLI1209BC)	+= pli1209bc.o
 obj-$(CONFIG_SENSORS_PM6764TR)	+= pm6764tr.o
 obj-$(CONFIG_SENSORS_PXE1610)	+= pxe1610.o
diff --git a/drivers/hwmon/pmbus/mpq8785.c b/drivers/hwmon/pmbus/mpq8785.c
new file mode 100644
index 000000000000..b9405dac7b09
--- /dev/null
+++ b/drivers/hwmon/pmbus/mpq8785.c
@@ -0,0 +1,89 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Driver for MPS MPQ8785 Step-Down Converter
+ */
+
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include "pmbus.h"
+
+static int mpq8785_identify(struct i2c_client *client,
+			    struct pmbus_driver_info *info)
+{
+	int vout_mode;
+
+	vout_mode = pmbus_read_byte_data(client, 0, PMBUS_VOUT_MODE);
+	if (vout_mode < 0 || vout_mode == 0xff)
+		return vout_mode < 0 ? vout_mode : -ENODEV;
+	switch (vout_mode >> 5) {
+	case 0:
+		info->format[PSC_VOLTAGE_OUT] = linear;
+		break;
+	case 1:
+	case 2:
+		info->format[PSC_VOLTAGE_OUT] = direct,
+		info->m[PSC_VOLTAGE_OUT] = 64;
+		info->b[PSC_VOLTAGE_OUT] = 0;
+		info->R[PSC_VOLTAGE_OUT] = 1;
+		break;
+	default:
+		return -ENODEV;
+	}
+
+	return 0;
+};
+
+static struct pmbus_driver_info mpq8785_info = {
+	.pages = 1,
+	.format[PSC_VOLTAGE_IN] = direct,
+	.format[PSC_CURRENT_OUT] = direct,
+	.format[PSC_TEMPERATURE] = direct,
+	.m[PSC_VOLTAGE_IN] = 4,
+	.b[PSC_VOLTAGE_IN] = 0,
+	.R[PSC_VOLTAGE_IN] = 1,
+	.m[PSC_CURRENT_OUT] = 16,
+	.b[PSC_CURRENT_OUT] = 0,
+	.R[PSC_CURRENT_OUT] = 0,
+	.m[PSC_TEMPERATURE] = 1,
+	.b[PSC_TEMPERATURE] = 0,
+	.R[PSC_TEMPERATURE] = 0,
+	.func[0] =
+		PMBUS_HAVE_VIN | PMBUS_HAVE_STATUS_INPUT |
+		PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT |
+		PMBUS_HAVE_IOUT | PMBUS_HAVE_STATUS_IOUT |
+		PMBUS_HAVE_TEMP | PMBUS_HAVE_STATUS_TEMP,
+	.identify = mpq8785_identify,
+};
+
+static int mpq8785_probe(struct i2c_client *client)
+{
+	return pmbus_do_probe(client, &mpq8785_info);
+};
+
+static const struct i2c_device_id mpq8785_id[] = {
+	{ "mpq8785", 0 },
+	{ },
+};
+MODULE_DEVICE_TABLE(i2c, mpq8785_id);
+
+static const struct of_device_id __maybe_unused mpq8785_of_match[] = {
+	{ .compatible = "mps,mpq8785" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, mpq8785_of_match);
+
+static struct i2c_driver mpq8785_driver = {
+	.driver = {
+		   .name = "mpq8785",
+		   .of_match_table = of_match_ptr(mpq8785_of_match),
+	},
+	.probe_new = mpq8785_probe,
+	.id_table = mpq8785_id,
+};
+
+module_i2c_driver(mpq8785_driver);
+
+MODULE_AUTHOR("Charles Hsu <ythsu0511@gmail.com>");
+MODULE_DESCRIPTION("PMBus driver for MPS MPQ8785");
+MODULE_LICENSE("GPL");
-- 
2.34.1