--- /dev/null
+.. SPDX-License-Identifier: GPL-2.0
+
+Kernel driver stpddc60
+======================
+
+Supported chips:
+
+ * ST STPDDC60
+
+ Prefix: 'stpddc60', 'bmr481'
+
+ Addresses scanned: -
+
+ Datasheet: https://flexpowermodules.com/documents/fpm-techspec-bmr481
+
+Author: Erik Rosen <erik.rosen@metormote.com>
+
+
+Description
+-----------
+
+This driver supports hardware monitoring for ST STPDDC60 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.
+
+The vout under- and over-voltage limits are set in relation to the commanded
+output voltage as a positive or negative offset in the interval 50mV to 400mV
+in 50mV steps. This means that the absolute values of the limits will change
+when the commanded output voltage changes. Also, care should be taken when
+writing to those limits since in the worst case the commanded output voltage
+could change at the same time as the limit is written to, wich will lead to
+unpredictable results.
+
+
+Platform data support
+---------------------
+
+The driver supports standard PMBus driver platform data.
+
+
+Sysfs entries
+-------------
+
+The following attributes are supported. Vin, iout, pout and temp 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_max Maximum output current.
+curr1_max_alarm Output current high alarm.
+curr1_crit Critical maximum output current.
+curr1_crit_alarm Output current critical high alarm.
+
+power1_label "pout1"
+power1_input Measured output power.
+power1_crit Critical maximum output power.
+power1_crit_alarm Output power 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.
+======================= ========================================================
--- /dev/null
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Hardware monitoring driver for the STPDDC60 controller
+ *
+ * Copyright (c) 2021 Flextronics International Sweden AB.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/pmbus.h>
+#include "pmbus.h"
+
+#define STPDDC60_MFR_READ_VOUT 0xd2
+#define STPDDC60_MFR_OV_LIMIT_OFFSET 0xe5
+#define STPDDC60_MFR_UV_LIMIT_OFFSET 0xe6
+
+static const struct i2c_device_id stpddc60_id[] = {
+ {"stpddc60", 0},
+ {"bmr481", 0},
+ {}
+};
+MODULE_DEVICE_TABLE(i2c, stpddc60_id);
+
+static struct pmbus_driver_info stpddc60_info = {
+ .pages = 1,
+ .func[0] = PMBUS_HAVE_VOUT | PMBUS_HAVE_STATUS_VOUT
+ | PMBUS_HAVE_VIN | PMBUS_HAVE_STATUS_INPUT
+ | PMBUS_HAVE_TEMP | PMBUS_HAVE_STATUS_TEMP
+ | PMBUS_HAVE_IOUT | PMBUS_HAVE_STATUS_IOUT
+ | PMBUS_HAVE_POUT,
+};
+
+/*
+ * Calculate the closest absolute offset between commanded vout value
+ * and limit value in steps of 50mv in the range 0 (50mv) to 7 (400mv).
+ * Return 0 if the upper limit is lower than vout or if the lower limit
+ * is higher than vout.
+ */
+static u8 stpddc60_get_offset(int vout, u16 limit, bool over)
+{
+ int offset;
+ long v, l;
+
+ v = 250 + (vout - 1) * 5; /* Convert VID to mv */
+ l = (limit * 1000L) >> 8; /* Convert LINEAR to mv */
+
+ if (over == (l < v))
+ return 0;
+
+ offset = DIV_ROUND_CLOSEST(abs(l - v), 50);
+
+ if (offset > 0)
+ offset--;
+
+ return clamp_val(offset, 0, 7);
+}
+
+/*
+ * Adjust the linear format word to use the given fixed exponent.
+ */
+static u16 stpddc60_adjust_linear(u16 word, s16 fixed)
+{
+ s16 e, m, d;
+
+ e = ((s16)word) >> 11;
+ m = ((s16)((word & 0x7ff) << 5)) >> 5;
+ d = e - fixed;
+
+ if (d >= 0)
+ m <<= d;
+ else
+ m >>= -d;
+
+ return clamp_val(m, 0, 0x3ff) | ((fixed << 11) & 0xf800);
+}
+
+/*
+ * The VOUT_COMMAND register uses the VID format but the vout alarm limit
+ * registers use the LINEAR format so we override VOUT_MODE here to force
+ * LINEAR format for all registers.
+ */
+static int stpddc60_read_byte_data(struct i2c_client *client, int page, int reg)
+{
+ int ret;
+
+ if (page > 0)
+ return -ENXIO;
+
+ switch (reg) {
+ case PMBUS_VOUT_MODE:
+ ret = 0x18;
+ break;
+ default:
+ ret = -ENODATA;
+ break;
+ }
+
+ return ret;
+}
+
+/*
+ * The vout related registers return values in LINEAR11 format when LINEAR16
+ * is expected. Clear the top 5 bits to set the exponent part to zero to
+ * convert the value to LINEAR16 format.
+ */
+static int stpddc60_read_word_data(struct i2c_client *client, int page,
+ int phase, int reg)
+{
+ int ret;
+
+ if (page > 0)
+ return -ENXIO;
+
+ switch (reg) {
+ case PMBUS_READ_VOUT:
+ ret = pmbus_read_word_data(client, page, phase,
+ STPDDC60_MFR_READ_VOUT);
+ if (ret < 0)
+ return ret;
+ ret &= 0x7ff;
+ break;
+ case PMBUS_VOUT_OV_FAULT_LIMIT:
+ case PMBUS_VOUT_UV_FAULT_LIMIT:
+ ret = pmbus_read_word_data(client, page, phase, reg);
+ if (ret < 0)
+ return ret;
+ ret &= 0x7ff;
+ break;
+ default:
+ ret = -ENODATA;
+ break;
+ }
+
+ return ret;
+}
+
+/*
+ * The vout under- and over-voltage limits are set as an offset relative to
+ * the commanded vout voltage. The vin, iout, pout and temp limits must use
+ * the same fixed exponent the chip uses to encode the data when read.
+ */
+static int stpddc60_write_word_data(struct i2c_client *client, int page,
+ int reg, u16 word)
+{
+ int ret;
+ u8 offset;
+
+ if (page > 0)
+ return -ENXIO;
+
+ switch (reg) {
+ case PMBUS_VOUT_OV_FAULT_LIMIT:
+ ret = pmbus_read_word_data(client, page, 0xff,
+ PMBUS_VOUT_COMMAND);
+ if (ret < 0)
+ return ret;
+ offset = stpddc60_get_offset(ret, word, true);
+ ret = pmbus_write_byte_data(client, page,
+ STPDDC60_MFR_OV_LIMIT_OFFSET,
+ offset);
+ break;
+ case PMBUS_VOUT_UV_FAULT_LIMIT:
+ ret = pmbus_read_word_data(client, page, 0xff,
+ PMBUS_VOUT_COMMAND);
+ if (ret < 0)
+ return ret;
+ offset = stpddc60_get_offset(ret, word, false);
+ ret = pmbus_write_byte_data(client, page,
+ STPDDC60_MFR_UV_LIMIT_OFFSET,
+ offset);
+ break;
+ case PMBUS_VIN_OV_FAULT_LIMIT:
+ case PMBUS_VIN_UV_FAULT_LIMIT:
+ case PMBUS_OT_FAULT_LIMIT:
+ case PMBUS_OT_WARN_LIMIT:
+ case PMBUS_IOUT_OC_FAULT_LIMIT:
+ case PMBUS_IOUT_OC_WARN_LIMIT:
+ case PMBUS_POUT_OP_FAULT_LIMIT:
+ ret = pmbus_read_word_data(client, page, 0xff, reg);
+ if (ret < 0)
+ return ret;
+ word = stpddc60_adjust_linear(word, ret >> 11);
+ ret = pmbus_write_word_data(client, page, reg, word);
+ break;
+ default:
+ ret = -ENODATA;
+ break;
+ }
+
+ return ret;
+}
+
+static int stpddc60_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 = &stpddc60_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_MFR_MODEL, device_id);
+ if (status < 0) {
+ dev_err(&client->dev, "Failed to read Manufacturer Model\n");
+ return status;
+ }
+ for (mid = stpddc60_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;
+ }
+
+ info->read_byte_data = stpddc60_read_byte_data;
+ info->read_word_data = stpddc60_read_word_data;
+ info->write_word_data = stpddc60_write_word_data;
+
+ status = pmbus_do_probe(client, info);
+ if (status < 0)
+ return status;
+
+ pmbus_set_update(client, PMBUS_VOUT_OV_FAULT_LIMIT, true);
+ pmbus_set_update(client, PMBUS_VOUT_UV_FAULT_LIMIT, true);
+
+ return 0;
+}
+
+static struct i2c_driver stpddc60_driver = {
+ .driver = {
+ .name = "stpddc60",
+ },
+ .probe_new = stpddc60_probe,
+ .id_table = stpddc60_id,
+};
+
+module_i2c_driver(stpddc60_driver);
+
+MODULE_AUTHOR("Erik Rosen <erik.rosen@metormote.com>");
+MODULE_DESCRIPTION("PMBus driver for ST STPDDC60");
+MODULE_LICENSE("GPL");
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