hwmon: (pmbus) Add pmbus driver for MAX15301

Add pmbus driver support for Maxim MAX15301 InTune Automatically
Compensated Digital PoL Controller with Driver and PMBus Telemetry

Even though the specification does not specifically mention it,
extensive empirical testing has revealed that auto-detection of
limit-registers will fail in a random fashion unless the delay
parameter is set to above about 80us. The default delay is set
to 100us to include some safety margin.

This patch is tested on a Flex BMR461 converter module.

Signed-off-by: Erik Rosen <erik.rosen@metormote.com>
Link: https://lore.kernel.org/r/20210419101251.24840-1-erik.rosen@metormote.com
[groeck: Added rationale for delay to driver header]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/hwmon/index.rst

@@ -115,6 +115,7 @@ Hardware Monitoring Kernel Drivers
    ltc4260
    ltc4261
    max127
+   max15301
    max16064
    max16065
    max1619

Documentation/hwmon/max15301.rst

@@ -0,0 +1,87 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Kernel driver max15301
+======================
+
+Supported chips:
+
+  * Maxim MAX15301
+
+    Prefix: 'max15301', 'bmr461'
+
+    Addresses scanned: -
+
+    Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX15301.pdf
+
+Author: Erik Rosen <erik.rosen@metormote.com>
+
+
+Description
+-----------
+
+This driver supports hardware monitoring for Maxim MAX15301 controller chip and
+compatible modules.
+
+The driver is a client driver to the core PMBus driver. Please see
+Documentation/hwmon/pmbus.rst and Documentation.hwmon/pmbus-core for details
+on PMBus client drivers.
+
+
+Usage Notes
+-----------
+
+This driver does not auto-detect devices. You will have to instantiate the
+devices explicitly. Please see Documentation/i2c/instantiating-devices.rst for
+details.
+
+
+Platform data support
+---------------------
+
+The driver supports standard PMBus driver platform data.
+
+
+Module parameters
+-----------------
+
+delay
+-----
+
+The controller requires a minimum interval between I2C bus accesses.
+The default interval is set to 100 us. For manual override, the driver
+provides a writeable module parameter, 'delay', which can be used to
+set the interval to a value between 0 and 65,535 microseconds.
+
+
+Sysfs entries
+-------------
+
+The following attributes are supported. Limits are read-write; all other
+attributes are read-only.
+
+======================= ========================================================
+in1_label		"vin"
+in1_input		Measured input voltage.
+in1_lcrit		Critical minimum input voltage.
+in1_crit		Critical maximum input voltage.
+in1_lcrit_alarm		Input voltage critical low alarm.
+in1_crit_alarm		Input voltage critical high alarm.
+
+in2_label		"vout1"
+in2_input		Measured output voltage.
+in2_lcrit		Critical minimum output Voltage.
+in2_crit		Critical maximum output voltage.
+in2_lcrit_alarm		Critical output voltage critical low alarm.
+in2_crit_alarm		Critical output voltage critical high alarm.
+
+curr1_label		"iout1"
+curr1_input		Measured output current.
+curr1_crit		Critical maximum output current.
+curr1_crit_alarm	Output current critical high alarm.
+
+temp1_input		Measured maximum temperature of all phases.
+temp1_max		Maximum temperature limit.
+temp1_max_alarm		High temperature alarm.
+temp1_crit		Critical maximum temperature limit.
+temp1_crit_alarm	Critical maximum temperature alarm.
+======================= ========================================================

MAINTAINERS

@@ -10791,6 +10791,13 @@ S:	Orphan
 F:	drivers/video/fbdev/matrox/matroxfb_*
 F:	include/uapi/linux/matroxfb.h
 
+MAX15301 DRIVER
+M:	Daniel Nilsson <daniel.nilsson@flex.com>
+L:	linux-hwmon@vger.kernel.org
+S:	Maintained
+F:	Documentation/hwmon/max15301.rst
+F:	drivers/hwmon/pmbus/max15301.c
+
 MAX16065 HARDWARE MONITOR DRIVER
 M:	Guenter Roeck <linux@roeck-us.net>
 L:	linux-hwmon@vger.kernel.org

drivers/hwmon/pmbus/Kconfig

@@ -176,6 +176,15 @@ config SENSORS_LTC3815
 	  This driver can also be built as a module. If so, the module will
 	  be called ltc3815.
 
+config SENSORS_MAX15301
+	tristate "Maxim MAX15301"
+	help
+	  If you say yes here you get hardware monitoring support for Maxim
+	  MAX15301, as well as for Flex BMR461.
+
+	  This driver can also be built as a module. If so, the module will
+	  be called max15301.
+
 config SENSORS_MAX16064
 	tristate "Maxim MAX16064"
 	help

drivers/hwmon/pmbus/Makefile

@@ -20,6 +20,7 @@ obj-$(CONFIG_SENSORS_ISL68137)	+= isl68137.o
 obj-$(CONFIG_SENSORS_LM25066)	+= lm25066.o
 obj-$(CONFIG_SENSORS_LTC2978)	+= ltc2978.o
 obj-$(CONFIG_SENSORS_LTC3815)	+= ltc3815.o
+obj-$(CONFIG_SENSORS_MAX15301)	+= max15301.o
 obj-$(CONFIG_SENSORS_MAX16064)	+= max16064.o
 obj-$(CONFIG_SENSORS_MAX16601)	+= max16601.o
 obj-$(CONFIG_SENSORS_MAX20730)	+= max20730.o

drivers/hwmon/pmbus/max15301.c

@@ -0,0 +1,189 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Hardware monitoring driver for Maxim MAX15301
+ *
+ * Copyright (c) 2021 Flextronics International Sweden AB
+ *
+ * Even though the specification does not specifically mention it,
+ * extensive empirical testing has revealed that auto-detection of
+ * limit-registers will fail in a random fashion unless the delay
+ * parameter is set to above about 80us. The default delay is set
+ * to 100us to include some safety margin.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/err.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/ktime.h>
+#include <linux/delay.h>
+#include <linux/pmbus.h>
+#include "pmbus.h"
+
+static const struct i2c_device_id max15301_id[] = {
+	{"bmr461", 0},
+	{"max15301", 0},
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, max15301_id);
+
+struct max15301_data {
+	int id;
+	ktime_t access;		/* Chip access time */
+	int delay;		/* Delay between chip accesses in us */
+	struct pmbus_driver_info info;
+};
+
+#define to_max15301_data(x)  container_of(x, struct max15301_data, info)
+
+#define MAX15301_WAIT_TIME		100	/* us	*/
+
+static ushort delay = MAX15301_WAIT_TIME;
+module_param(delay, ushort, 0644);
+MODULE_PARM_DESC(delay, "Delay between chip accesses in us");
+
+static struct max15301_data max15301_data = {
+	.info = {
+		.pages = 1,
+		.func[0] = PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT
+			| PMBUS_HAVE_VIN | PMBUS_HAVE_STATUS_INPUT
+			| PMBUS_HAVE_TEMP | PMBUS_HAVE_TEMP2
+			| PMBUS_HAVE_STATUS_TEMP
+			| PMBUS_HAVE_IOUT | PMBUS_HAVE_STATUS_IOUT,
+	}
+};
+
+/* This chip needs a delay between accesses */
+static inline void max15301_wait(const struct max15301_data *data)
+{
+	if (data->delay) {
+		s64 delta = ktime_us_delta(ktime_get(), data->access);
+
+		if (delta < data->delay)
+			udelay(data->delay - delta);
+	}
+}
+
+static int max15301_read_word_data(struct i2c_client *client, int page,
+				   int phase, int reg)
+{
+	const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
+	struct max15301_data *data = to_max15301_data(info);
+	int ret;
+
+	if (page > 0)
+		return -ENXIO;
+
+	if (reg >= PMBUS_VIRT_BASE)
+		return -ENXIO;
+
+	max15301_wait(data);
+	ret = pmbus_read_word_data(client, page, phase, reg);
+	data->access = ktime_get();
+
+	return ret;
+}
+
+static int max15301_read_byte_data(struct i2c_client *client, int page, int reg)
+{
+	const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
+	struct max15301_data *data = to_max15301_data(info);
+	int ret;
+
+	if (page > 0)
+		return -ENXIO;
+
+	max15301_wait(data);
+	ret = pmbus_read_byte_data(client, page, reg);
+	data->access = ktime_get();
+
+	return ret;
+}
+
+static int max15301_write_word_data(struct i2c_client *client, int page, int reg,
+				    u16 word)
+{
+	const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
+	struct max15301_data *data = to_max15301_data(info);
+	int ret;
+
+	if (page > 0)
+		return -ENXIO;
+
+	if (reg >= PMBUS_VIRT_BASE)
+		return -ENXIO;
+
+	max15301_wait(data);
+	ret = pmbus_write_word_data(client, page, reg, word);
+	data->access = ktime_get();
+
+	return ret;
+}
+
+static int max15301_write_byte(struct i2c_client *client, int page, u8 value)
+{
+	const struct pmbus_driver_info *info = pmbus_get_driver_info(client);
+	struct max15301_data *data = to_max15301_data(info);
+	int ret;
+
+	if (page > 0)
+		return -ENXIO;
+
+	max15301_wait(data);
+	ret = pmbus_write_byte(client, page, value);
+	data->access = ktime_get();
+
+	return ret;
+}
+
+static int max15301_probe(struct i2c_client *client)
+{
+	int status;
+	u8 device_id[I2C_SMBUS_BLOCK_MAX + 1];
+	const struct i2c_device_id *mid;
+	struct pmbus_driver_info *info = &max15301_data.info;
+
+	if (!i2c_check_functionality(client->adapter,
+				     I2C_FUNC_SMBUS_READ_BYTE_DATA
+				     | I2C_FUNC_SMBUS_BLOCK_DATA))
+		return -ENODEV;
+
+	status = i2c_smbus_read_block_data(client, PMBUS_IC_DEVICE_ID, device_id);
+	if (status < 0) {
+		dev_err(&client->dev, "Failed to read Device Id\n");
+		return status;
+	}
+	for (mid = max15301_id; mid->name[0]; mid++) {
+		if (!strncasecmp(mid->name, device_id, strlen(mid->name)))
+			break;
+	}
+	if (!mid->name[0]) {
+		dev_err(&client->dev, "Unsupported device\n");
+		return -ENODEV;
+	}
+
+	max15301_data.delay = delay;
+
+	info->read_byte_data = max15301_read_byte_data;
+	info->read_word_data = max15301_read_word_data;
+	info->write_byte = max15301_write_byte;
+	info->write_word_data = max15301_write_word_data;
+
+	return pmbus_do_probe(client, info);
+}
+
+static struct i2c_driver max15301_driver = {
+	.driver = {
+		   .name = "max15301",
+		   },
+	.probe_new = max15301_probe,
+	.id_table = max15301_id,
+};
+
+module_i2c_driver(max15301_driver);
+
+MODULE_AUTHOR("Erik Rosen <erik.rosen@metormote.com>");
+MODULE_DESCRIPTION("PMBus driver for Maxim MAX15301");
+MODULE_LICENSE("GPL");