Support setting the reference voltage in the device tree.
Rework of driver structure, put chip specific data in a separate
structure and assign it depending on device id from platform data or
DT match.
Extend the device documentation and add new documentation for the
devicetree bindings.
Also change S_IRUGO to the better readable 0444, which fixes a
checkpatch warning.

Signed-off-by: Clemens Gruber <clemens.gru...@pqgruber.com>
---
 .../devicetree/bindings/hwmon/mcp3021.txt          |  21 +++
 Documentation/hwmon/mcp3021                        |   5 +
 drivers/hwmon/mcp3021.c                            | 184 ++++++++++++++-------
 3 files changed, 149 insertions(+), 61 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/hwmon/mcp3021.txt

diff --git a/Documentation/devicetree/bindings/hwmon/mcp3021.txt 
b/Documentation/devicetree/bindings/hwmon/mcp3021.txt
new file mode 100644
index 0000000..e1d1e62
--- /dev/null
+++ b/Documentation/devicetree/bindings/hwmon/mcp3021.txt
@@ -0,0 +1,21 @@
+mcp3021 properties
+
+Required properties:
+- compatible: Must be one of the following:
+       - "microchip,mcp3021" for mcp3021
+       - "microchip,mcp3221" for mcp3221
+- reg: I2C address
+
+Optional properties:
+
+- reference-voltage
+       Reference voltage in millivolt (mV)
+
+Example:
+
+mcp3021@4d {
+       compatible = "microchip,mcp3021";
+       reg = <0x4d>;
+
+       reference-voltage = <4500>; /* 4.5 V */
+};
diff --git a/Documentation/hwmon/mcp3021 b/Documentation/hwmon/mcp3021
index 74a6b72..55792c3 100644
--- a/Documentation/hwmon/mcp3021
+++ b/Documentation/hwmon/mcp3021
@@ -12,6 +12,7 @@ Supported chips:
 Authors:
    Mingkai Hu
    Sven Schuchmann <schuchm...@schleissheimer.de>
+   Clemens Gruber <clemens.gru...@pqgruber.com>
 
 Description
 -----------
@@ -27,3 +28,7 @@ Communication to the MCP3021/MCP3221  is performed using a 
2-wire I2C
 compatible interface. Standard (100 kHz) and Fast (400 kHz) I2C modes are
 available. The default I2C device address is 0x4d (contact the Microchip
 factory for additional address options).
+
+The reference-voltage used in the conversion can be set via platform data or
+device tree. Please refer to Documentation/devicetree/bindings/i2c/mcp3021.txt
+for information about the bindings if the device tree is used.
diff --git a/drivers/hwmon/mcp3021.c b/drivers/hwmon/mcp3021.c
index 972444a..ebbd3d2 100644
--- a/drivers/hwmon/mcp3021.c
+++ b/drivers/hwmon/mcp3021.c
@@ -4,6 +4,7 @@
  * Copyright (C) 2008-2009, 2012 Freescale Semiconductor, Inc.
  * Author: Mingkai Hu <mingkai...@freescale.com>
  * Reworked by Sven Schuchmann <schuchm...@schleissheimer.de>
+ * Copyright (C) 2016 Clemens Gruber <clemens.gru...@pqgruber.com>
  *
  * This driver export the value of analog input voltage to sysfs, the
  * voltage unit is mV. Through the sysfs interface, lm-sensors tool
@@ -22,35 +23,74 @@
 #include <linux/i2c.h>
 #include <linux/err.h>
 #include <linux/device.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
 
-/* Vdd info */
+/* Vdd / reference voltage */
 #define MCP3021_VDD_MAX                5500
 #define MCP3021_VDD_MIN                2700
-#define MCP3021_VDD_REF                3300
+#define MCP3021_VDD_DEFAULT    3300
 
-/* output format */
-#define MCP3021_SAR_SHIFT      2
-#define MCP3021_SAR_MASK       0x3ff
-#define MCP3021_OUTPUT_RES     10      /* 10-bit resolution */
+struct mcp3021_chip_info {
+       u16 sar_shift;
+       u16 sar_mask;
+       u8 output_res;
+};
+
+struct mcp3021_data {
+       struct device *hwmon_dev;
+       const struct mcp3021_chip_info *chip_info;
+       u32 vdd; /* Supply and reference voltage for AD conversion */
+};
 
-#define MCP3221_SAR_SHIFT      0
-#define MCP3221_SAR_MASK       0xfff
-#define MCP3221_OUTPUT_RES     12      /* 12-bit resolution */
+static int mcp3021_probe(struct i2c_client *client,
+       const struct i2c_device_id *id);
+static int mcp3021_remove(struct i2c_client *client);
 
-enum chips {
+enum {
        mcp3021,
        mcp3221
 };
 
-/*
- * Client data (each client gets its own)
- */
-struct mcp3021_data {
-       struct device *hwmon_dev;
-       u32 vdd;        /* device power supply */
-       u16 sar_shift;
-       u16 sar_mask;
-       u8 output_res;
+static const struct i2c_device_id mcp3021_id[] = {
+       { "mcp3021", mcp3021 },
+       { "mcp3221", mcp3221 },
+       { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(i2c, mcp3021_id);
+
+static const struct mcp3021_chip_info mcp3021_chip_info_tbl[] = {
+       [mcp3021] = {
+               .sar_shift = 2,
+               .sar_mask = 0x3ff,
+               .output_res = 10,       /* 10-bit resolution */
+       },
+       [mcp3221] = {
+               .sar_shift = 0,
+               .sar_mask = 0xfff,
+               .output_res = 12,       /* 12-bit resolution */
+       },
+};
+
+#ifdef CONFIG_OF
+static const struct of_device_id of_mcp3021_match[] = {
+       { .compatible = "microchip,mcp3021", .data = (void *)mcp3021 },
+       { .compatible = "microchip,mcp3221", .data = (void *)mcp3221 },
+       { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, of_mcp3021_match);
+#endif
+
+static struct i2c_driver mcp3021_driver = {
+       .driver = {
+               .name = "mcp3021",
+#ifdef CONFIG_OF
+               .of_match_table = of_match_ptr(of_mcp3021_match),
+#endif
+       },
+       .probe = mcp3021_probe,
+       .remove = mcp3021_remove,
+       .id_table = mcp3021_id,
 };
 
 static int mcp3021_read16(struct i2c_client *client)
@@ -73,14 +113,15 @@ static int mcp3021_read16(struct i2c_client *client)
         * The ten-bit output code is composed of the lower 4-bit of the
         * first byte and the upper 6-bit of the second byte.
         */
-       reg = (reg >> data->sar_shift) & data->sar_mask;
+       reg = (reg >> data->chip_info->sar_shift) & data->chip_info->sar_mask;
 
        return reg;
 }
 
 static inline u16 volts_from_reg(struct mcp3021_data *data, u16 val)
 {
-       return DIV_ROUND_CLOSEST(data->vdd * val, 1 << data->output_res);
+       return DIV_ROUND_CLOSEST(data->vdd * val,
+                                1 << data->chip_info->output_res);
 }
 
 static ssize_t show_in_input(struct device *dev, struct device_attribute *attr,
@@ -99,46 +140,83 @@ static ssize_t show_in_input(struct device *dev, struct 
device_attribute *attr,
        return sprintf(buf, "%d\n", in_input);
 }
 
-static DEVICE_ATTR(in0_input, S_IRUGO, show_in_input, NULL);
+static DEVICE_ATTR(in0_input, 0444, show_in_input, NULL);
 
-static int mcp3021_probe(struct i2c_client *client,
+#ifdef CONFIG_OF
+static int mcp3021_probe_dt(struct i2c_client *client,
                                const struct i2c_device_id *id)
 {
-       int err;
-       struct mcp3021_data *data = NULL;
+       struct mcp3021_data *data = i2c_get_clientdata(client);
+       struct device_node *np = client->dev.of_node;
+       const struct of_device_id *match;
+       int devid, ret;
 
-       if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+       match = of_match_device(of_mcp3021_match, &client->dev);
+       if (!match)
                return -ENODEV;
 
-       data = devm_kzalloc(&client->dev, sizeof(struct mcp3021_data),
-                           GFP_KERNEL);
-       if (!data)
-               return -ENOMEM;
+       devid = (int)(uintptr_t)match->data;
+       data->chip_info = &mcp3021_chip_info_tbl[devid];
 
-       i2c_set_clientdata(client, data);
-
-       switch (id->driver_data) {
-       case mcp3021:
-               data->sar_shift = MCP3021_SAR_SHIFT;
-               data->sar_mask = MCP3021_SAR_MASK;
-               data->output_res = MCP3021_OUTPUT_RES;
-               break;
-
-       case mcp3221:
-               data->sar_shift = MCP3221_SAR_SHIFT;
-               data->sar_mask = MCP3221_SAR_MASK;
-               data->output_res = MCP3221_OUTPUT_RES;
-               break;
+       ret = of_property_read_u32(np, "reference-voltage", &data->vdd);
+       if (ret) {
+               /* Fallback: Use default value */
+               data->vdd = MCP3021_VDD_DEFAULT;
+               return 0;
        }
 
+       if (data->vdd > MCP3021_VDD_MAX || data->vdd < MCP3021_VDD_MIN)
+               return -EINVAL;
+
+       return 0;
+}
+#else
+static int mcp3021_probe_dt(struct i2c_client *client,
+                               const struct i2c_device_id *id)
+{
+       return 1;
+}
+#endif
+
+static int mcp3021_probe_pdata(struct i2c_client *client,
+                               const struct i2c_device_id *id)
+{
+       struct mcp3021_data *data = i2c_get_clientdata(client);
+
+       data->chip_info = &mcp3021_chip_info_tbl[id->driver_data];
+
        if (dev_get_platdata(&client->dev)) {
                data->vdd = *(u32 *)dev_get_platdata(&client->dev);
                if (data->vdd > MCP3021_VDD_MAX || data->vdd < MCP3021_VDD_MIN)
                        return -EINVAL;
        } else {
-               data->vdd = MCP3021_VDD_REF;
+               data->vdd = MCP3021_VDD_DEFAULT;
        }
 
+       return 0;
+}
+
+static int mcp3021_probe(struct i2c_client *client,
+                               const struct i2c_device_id *id)
+{
+       struct mcp3021_data *data = NULL;
+       int err;
+
+       if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+               return -ENODEV;
+
+       data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
+       if (!data)
+               return -ENOMEM;
+
+       i2c_set_clientdata(client, data);
+
+       err = mcp3021_probe_dt(client, id);
+       if (err > 0)
+               mcp3021_probe_pdata(client, id);
+       else if (err < 0)
+               return err;
+
        err = sysfs_create_file(&client->dev.kobj, &dev_attr_in0_input.attr);
        if (err)
                return err;
@@ -166,22 +244,6 @@ static int mcp3021_remove(struct i2c_client *client)
        return 0;
 }
 
-static const struct i2c_device_id mcp3021_id[] = {
-       { "mcp3021", mcp3021 },
-       { "mcp3221", mcp3221 },
-       { }
-};
-MODULE_DEVICE_TABLE(i2c, mcp3021_id);
-
-static struct i2c_driver mcp3021_driver = {
-       .driver = {
-               .name = "mcp3021",
-       },
-       .probe = mcp3021_probe,
-       .remove = mcp3021_remove,
-       .id_table = mcp3021_id,
-};
-
 module_i2c_driver(mcp3021_driver);
 
 MODULE_AUTHOR("Mingkai Hu <mingkai...@freescale.com>");
-- 
2.10.0

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