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>

3 files changed, 199 insertions, 0 deletions

diff --git a/drivers/hwmon/pmbus/Kconfig b/drivers/hwmon/pmbus/Kconfig
index e9727176b167..37a5c39784fa 100644
--- a/drivers/hwmon/pmbus/Kconfig
+++ b/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
diff --git a/drivers/hwmon/pmbus/Makefile b/drivers/hwmon/pmbus/Makefile
index 4ca98e9005f1..f8dcc27cd56a 100644
--- a/drivers/hwmon/pmbus/Makefile
+++ b/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
diff --git a/drivers/hwmon/pmbus/max15301.c b/drivers/hwmon/pmbus/max15301.c
new file mode 100644
index 000000000000..727455e5740b
--- /dev/null
+++ b/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");