The Gateworks System Controller has a hwmon sub-component that exposes
up to 16 ADC's, some of which are temperature sensors, others which are
voltage inputs. The ADC configuration (register mapping and name) is
configured via device-tree and varies board to board.

Cc: Guenter Roeck <li...@roeck-us.net>
Signed-off-by: Tim Harvey <thar...@gateworks.com>
---
v2:
- change license comment style
- remove DEBUG
- simplify regmap_bulk_read err check
- remove break after returns in switch statement
- fix fan setpoint buffer address
- remove unnecessary parens
- consistently use struct device *dev pointer
- change license/comment block
- add validation for hwmon child node props
- move parsing of of to own function
- use strlcpy to ensure null termination
- fix static array sizes and removed unnecessary initializers
- dynamically allocate channels
- fix fan input label
- support platform data
- fixed whitespace issues

 drivers/hwmon/Kconfig                   |   9 +
 drivers/hwmon/Makefile                  |   1 +
 drivers/hwmon/gsc-hwmon.c               | 330 ++++++++++++++++++++++++++++++++
 include/linux/platform_data/gsc_hwmon.h |  34 ++++
 4 files changed, 374 insertions(+)
 create mode 100644 drivers/hwmon/gsc-hwmon.c
 create mode 100644 include/linux/platform_data/gsc_hwmon.h

diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 7ad0176..e052798b 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -475,6 +475,15 @@ config SENSORS_F75375S
          This driver can also be built as a module.  If so, the module
          will be called f75375s.
 
+config SENSORS_GSC
+        tristate "Gateworks System Controller ADC"
+        depends on MFD_GSC
+        help
+          Support for the Gateworks System Controller A/D converters.
+
+         To compile this driver as a module, choose M here:
+         the module will be called gsc-hwmon.
+
 config SENSORS_MC13783_ADC
         tristate "Freescale MC13783/MC13892 ADC"
         depends on MFD_MC13XXX
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index 0fe489f..835a536 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -69,6 +69,7 @@ obj-$(CONFIG_SENSORS_G760A)   += g760a.o
 obj-$(CONFIG_SENSORS_G762)     += g762.o
 obj-$(CONFIG_SENSORS_GL518SM)  += gl518sm.o
 obj-$(CONFIG_SENSORS_GL520SM)  += gl520sm.o
+obj-$(CONFIG_SENSORS_GSC)      += gsc-hwmon.o
 obj-$(CONFIG_SENSORS_GPIO_FAN) += gpio-fan.o
 obj-$(CONFIG_SENSORS_HIH6130)  += hih6130.o
 obj-$(CONFIG_SENSORS_ULTRA45)  += ultra45_env.o
diff --git a/drivers/hwmon/gsc-hwmon.c b/drivers/hwmon/gsc-hwmon.c
new file mode 100644
index 0000000..cf55457
--- /dev/null
+++ b/drivers/hwmon/gsc-hwmon.c
@@ -0,0 +1,330 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2018 Gateworks Corporation
+ *
+ * This driver registers Linux HWMON attributes for GSC ADC's
+ */
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/mfd/gsc.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+#include <linux/platform_data/gsc_hwmon.h>
+
+#define GSC_HWMON_MAX_TEMP_CH  16
+#define GSC_HWMON_MAX_IN_CH    16
+#define GSC_HWMON_MAX_FAN_CH   6
+
+struct gsc_hwmon_data {
+       struct gsc_dev *gsc;
+       struct device *dev;
+       struct gsc_hwmon_platform_data *pdata;
+       const struct gsc_hwmon_channel *temp_ch[GSC_HWMON_MAX_TEMP_CH];
+       const struct gsc_hwmon_channel *in_ch[GSC_HWMON_MAX_IN_CH];
+       const struct gsc_hwmon_channel *fan_ch[GSC_HWMON_MAX_FAN_CH];
+       u32 temp_config[GSC_HWMON_MAX_TEMP_CH + 1];
+       u32 in_config[GSC_HWMON_MAX_IN_CH + 1];
+       u32 fan_config[GSC_HWMON_MAX_FAN_CH + 1];
+       struct hwmon_channel_info temp_info;
+       struct hwmon_channel_info in_info;
+       struct hwmon_channel_info fan_info;
+       const struct hwmon_channel_info *info[4];
+       struct hwmon_chip_info chip;
+};
+
+static int
+gsc_hwmon_read(struct device *dev, enum hwmon_sensor_types type, u32 attr,
+              int channel, long *val)
+{
+       struct gsc_hwmon_data *hwmon = dev_get_drvdata(dev);
+       int sz, ret;
+       u8 reg;
+       u8 buf[3];
+
+       dev_dbg(dev, "%s type=%d attr=%d channel=%d\n", __func__, type, attr,
+               channel);
+       switch (type) {
+       case hwmon_in:
+               if (channel > GSC_HWMON_MAX_IN_CH)
+                       return -EOPNOTSUPP;
+               reg = hwmon->in_ch[channel]->reg;
+               sz = 3;
+               break;
+       case hwmon_temp:
+               if (channel > GSC_HWMON_MAX_TEMP_CH)
+                       return -EOPNOTSUPP;
+               reg = hwmon->temp_ch[channel]->reg;
+               sz = 2;
+               break;
+       case hwmon_fan:
+               if (channel > GSC_HWMON_MAX_FAN_CH)
+                       return -EOPNOTSUPP;
+               reg = hwmon->fan_ch[channel]->reg;
+               sz = 2;
+               break;
+       default:
+               return -EOPNOTSUPP;
+       }
+
+       ret = regmap_bulk_read(hwmon->gsc->regmap_hwmon, reg, &buf, sz);
+       if (ret)
+               return ret;
+
+       *val = 0;
+       while (sz-- > 0)
+               *val |= (buf[sz] << (8*sz));
+       if ((type == hwmon_temp) && *val > 0x8000)
+               *val -= 0xffff;
+
+       return 0;
+}
+
+static int
+gsc_hwmon_read_string(struct device *dev, enum hwmon_sensor_types type,
+                     u32 attr, int channel, const char **buf)
+{
+       struct gsc_hwmon_data *hwmon = dev_get_drvdata(dev);
+
+       dev_dbg(dev, "%s type=%d attr=%d channel=%d\n", __func__, type, attr,
+               channel);
+       switch (type) {
+       case hwmon_in:
+               if (channel > GSC_HWMON_MAX_IN_CH)
+                       return -EOPNOTSUPP;
+               *buf = hwmon->in_ch[channel]->name;
+               break;
+       case hwmon_temp:
+               if (channel > GSC_HWMON_MAX_TEMP_CH)
+                       return -EOPNOTSUPP;
+               *buf = hwmon->temp_ch[channel]->name;
+               break;
+       case hwmon_fan:
+               if (channel > GSC_HWMON_MAX_FAN_CH)
+                       return -EOPNOTSUPP;
+               *buf = hwmon->fan_ch[channel]->name;
+               break;
+       default:
+               return -ENOTSUPP;
+       }
+
+       return 0;
+}
+
+static int
+gsc_hwmon_write(struct device *dev, enum hwmon_sensor_types type, u32 attr,
+               int channel, long val)
+{
+       struct gsc_hwmon_data *hwmon = dev_get_drvdata(dev);
+       u8 buf[3];
+
+       dev_dbg(dev, "%s type=%d attr=%d channel=%d\n", __func__, type, attr,
+               channel);
+       switch (type) {
+       case hwmon_fan:
+               if (channel == GSC_HWMON_MAX_FAN_CH)
+                       return -EOPNOTSUPP;
+               buf[0] = val & 0xff;
+               buf[1] = (val >> 8) & 0xff;
+               return regmap_bulk_write(hwmon->gsc->regmap_hwmon,
+                                        hwmon->fan_ch[channel]->reg, buf, 2);
+       default:
+               break;
+       }
+
+       return -EOPNOTSUPP;
+}
+
+static umode_t
+gsc_hwmon_is_visible(const void *_data, enum hwmon_sensor_types type, u32 attr,
+                    int ch)
+{
+       const struct gsc_hwmon_data *hwmon = _data;
+       struct device *dev = hwmon->gsc->dev;
+       umode_t mode = 0;
+
+       switch (type) {
+       case hwmon_fan:
+               mode = S_IRUGO;
+               if (attr == hwmon_fan_input)
+                       mode |= S_IWUSR;
+               break;
+       case hwmon_temp:
+       case hwmon_in:
+               mode = S_IRUGO;
+               break;
+       default:
+               break;
+       }
+       dev_dbg(dev, "%s type=%d attr=%d ch=%d mode=0x%x\n", __func__, type,
+               attr, ch, mode);
+
+       return mode;
+}
+
+static const struct hwmon_ops gsc_hwmon_ops = {
+       .is_visible = gsc_hwmon_is_visible,
+       .read = gsc_hwmon_read,
+       .read_string = gsc_hwmon_read_string,
+       .write = gsc_hwmon_write,
+};
+
+static struct gsc_hwmon_platform_data *
+gsc_hwmon_get_devtree_pdata(struct device *dev)
+{
+       struct gsc_hwmon_platform_data *pdata;
+       struct gsc_hwmon_channel *ch;
+       struct fwnode_handle *child;
+       int nchannels;
+
+       nchannels = device_get_child_node_count(dev);
+       dev_dbg(dev, "channels=%d\n", nchannels);
+       if (nchannels == 0)
+               return ERR_PTR(-ENODEV);
+
+       pdata = devm_kzalloc(dev,
+                            sizeof(*pdata) + nchannels * sizeof(*ch),
+                            GFP_KERNEL);
+       if (!pdata)
+               return ERR_PTR(-ENOMEM);
+       ch = (struct gsc_hwmon_channel *)(pdata + 1);
+       pdata->channels = ch;
+       pdata->nchannels = nchannels;
+
+       /* allocate structures for channels and count instances of each type */
+       device_for_each_child_node(dev, child) {
+               if (fwnode_property_read_string(child, "label", &ch->name)) {
+                       dev_err(dev, "channel without label\n");
+                       fwnode_handle_put(child);
+                       return ERR_PTR(-EINVAL);
+               }
+               if (fwnode_property_read_u32(child, "reg", &ch->reg)) {
+                       dev_err(dev, "channel without reg\n");
+                       fwnode_handle_put(child);
+                       return ERR_PTR(-EINVAL);
+               }
+               if (fwnode_property_read_u32(child, "type", &ch->type)) {
+                       dev_err(dev, "channel without type\n");
+                       fwnode_handle_put(child);
+                       return ERR_PTR(-EINVAL);
+               }
+               dev_dbg(dev, "of: reg=0x%02x type=%d %s\n", ch->reg, ch->type,
+                       ch->name);
+               ch++;
+       }
+
+       return pdata;
+}
+
+static int gsc_hwmon_probe(struct platform_device *pdev)
+{
+       struct gsc_dev *gsc = dev_get_drvdata(pdev->dev.parent);
+       struct device *dev = &pdev->dev;
+       struct gsc_hwmon_platform_data *pdata = dev_get_platdata(dev);
+       struct gsc_hwmon_data *hwmon;
+       int i, i_in, i_temp, i_fan;
+
+       if (!pdata) {
+               pdata = gsc_hwmon_get_devtree_pdata(dev);
+               if (IS_ERR(pdata))
+                       return PTR_ERR(pdata);
+       }
+
+       hwmon = devm_kzalloc(dev, sizeof(*hwmon), GFP_KERNEL);
+       if (!hwmon)
+               return -ENOMEM;
+       hwmon->gsc = gsc;
+       hwmon->pdata = pdata;
+
+       for (i = 0, i_in = 0, i_temp = 0, i_fan = 0;
+            i < hwmon->pdata->nchannels; i++) {
+               const struct gsc_hwmon_channel *ch = &pdata->channels[i];
+
+               if (ch->reg > GSC_HWMON_MAX_REG) {
+                       dev_err(dev, "invalid reg: 0x%02x\n", ch->reg);
+                       return -EINVAL;
+               }
+               switch (ch->type) {
+               case type_temperature:
+                       if (i_temp == GSC_HWMON_MAX_TEMP_CH) {
+                               dev_err(dev, "too many temp channels\n");
+                               return -EINVAL;
+                       }
+                       hwmon->temp_ch[i_temp] = ch;
+                       hwmon->temp_config[i_temp] = HWMON_T_INPUT |
+                                                    HWMON_T_LABEL;
+                       i_temp++;
+                       break;
+               case type_voltage:
+                       if (i_in == GSC_HWMON_MAX_IN_CH) {
+                               dev_err(dev, "too many voltage channels\n");
+                               return -EINVAL;
+                       }
+                       hwmon->in_ch[i_in] = ch;
+                       hwmon->in_config[i_in] =
+                               HWMON_I_INPUT | HWMON_I_LABEL;
+                       i_in++;
+                       break;
+               case type_fan:
+                       if (i_fan == GSC_HWMON_MAX_FAN_CH) {
+                               dev_err(dev, "too many voltage channels\n");
+                               return -EINVAL;
+                       }
+                       hwmon->fan_ch[i_fan] = ch;
+                       hwmon->fan_config[i_fan] =
+                               HWMON_F_INPUT | HWMON_F_LABEL;
+                       i_fan++;
+                       break;
+               default:
+                       dev_err(dev, "invalid type: %d\n", ch->type);
+                       return -EINVAL;
+               }
+               dev_dbg(dev, "pdata: reg=0x%02x type=%d %s\n", ch->reg,
+                       ch->type, ch->name);
+       }
+
+       /* terminate channel config lists */
+       hwmon->temp_config[i_temp] = 0;
+       hwmon->in_config[i_in] = 0;
+       hwmon->fan_config[i_fan] = 0;
+
+       /* setup config structures */
+       hwmon->chip.ops = &gsc_hwmon_ops;
+       hwmon->chip.info = hwmon->info;
+       hwmon->info[0] = &hwmon->temp_info;
+       hwmon->info[1] = &hwmon->in_info;
+       hwmon->info[2] = &hwmon->fan_info;
+       hwmon->temp_info.type = hwmon_temp;
+       hwmon->temp_info.config = hwmon->temp_config;
+       hwmon->in_info.type = hwmon_in;
+       hwmon->in_info.config = hwmon->in_config;
+       hwmon->fan_info.type = hwmon_fan;
+       hwmon->fan_info.config = hwmon->fan_config;
+
+       hwmon->dev = devm_hwmon_device_register_with_info(dev,
+                                                         KBUILD_MODNAME, hwmon,
+                                                         &hwmon->chip, NULL);
+       return PTR_ERR_OR_ZERO(hwmon->dev);
+}
+
+static const struct of_device_id gsc_hwmon_of_match[] = {
+       { .compatible = "gw,gsc-hwmon", },
+       {}
+};
+
+static struct platform_driver gsc_hwmon_driver = {
+       .driver = {
+               .name = KBUILD_MODNAME,
+               .of_match_table = gsc_hwmon_of_match,
+       },
+       .probe = gsc_hwmon_probe,
+};
+
+module_platform_driver(gsc_hwmon_driver);
+
+MODULE_AUTHOR("Tim Harvey <thar...@gateworks.com>");
+MODULE_DESCRIPTION("GSC hardware monitor driver");
+MODULE_LICENSE("GPL v2");
diff --git a/include/linux/platform_data/gsc_hwmon.h 
b/include/linux/platform_data/gsc_hwmon.h
new file mode 100644
index 0000000..ba4f811
--- /dev/null
+++ b/include/linux/platform_data/gsc_hwmon.h
@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _GSC_HWMON_H
+#define _GSC_HWMON_H
+
+enum gsc_hwmon_type {
+       type_temperature,
+       type_voltage,
+       type_fan,
+};
+
+/**
+ * struct gsc_hwmon_channel - configuration parameters
+ * @reg:  I2C register offset
+ * @type: channel type
+ * @name: channel name
+ */
+struct gsc_hwmon_channel {
+       unsigned int reg;
+       unsigned int type;
+       const char *name;
+};
+
+/**
+ * struct gsc_hwmon_platform_data - platform data for gsc_hwmon driver
+ * @channels:  pointer to array of gsc_hwmon_channel structures
+ *             describing channels
+ * @nchannels: number of elements in @channels array
+ */
+struct gsc_hwmon_platform_data {
+       const struct gsc_hwmon_channel *channels;
+       int nchannels;
+};
+
+#endif
-- 
2.7.4

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