hwmon: (ds1621) Add ds1631 chip support to ds1621 driver and documentation

Add definitions, information, and code for ds1631 chip support
to the ds1621 driver.

Signed-off-by: Robert Coulson <rob.coulson@gmail.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

3 files changed, 45 insertions, 10 deletions

diff --git a/Documentation/hwmon/ds1621 b/Documentation/hwmon/ds1621
index b61e77c6b1cb..1ebaa2485770 100644
--- a/Documentation/hwmon/ds1621
+++ b/Documentation/hwmon/ds1621
@@ -14,6 +14,11 @@ Supported chips:
     Addresses scanned: I2C 0x48 - 0x4f
     Datasheet: Publicly available from www.datasheetarchive.com
 
+  * Maxim Integrated DS1631
+    Prefix: 'ds1631'
+    Addresses scanned: I2C 0x48 - 0x4f
+    Datasheet: Publicly available from www.maximintegrated.com
+
   * Maxim Integrated DS1721
     Prefix: 'ds1721'
     Addresses scanned: I2C 0x48 - 0x4f
@@ -69,7 +74,15 @@ Temperature conversion of the DS1621 takes up to 1000ms; internal access to
 non-volatile registers may last for 10ms or below.
 
 The DS1625 is pin compatible and functionally equivalent with the DS1621,
-but the DS1621 is meant to replace it.
+but the DS1621 is meant to replace it. The DS1631 and DS1721 are also
+pin compatible with the DS1621, but provide multi-resolution support.
+
+Since there is no version register, there is no unique identification
+for these devices. In addition, the DS1631 and DS1721 will emulate a
+DS1621 device, if not explicitly instantiated (why? because the detect
+function compares the temperature register values bits and checks for a
+9-bit resolution). Therefore, for correct device identification and
+functionality, explicit device instantiation is required.
 
 The DS1721 is pin compatible with the DS1621, has an accuracy of +/- 1.0
 degree Celsius over a -10 to +85 degree range, a minimum/maximum alarm
@@ -78,9 +91,17 @@ time of 750ms.
 
 In addition, the DS1721 supports four resolution settings from 9 to 12 bits
 (defined in degrees C per LSB: 0.5, 0.25, 0.125, and 0.0625, respectifully),
-that are set at device power on to the highest resolution: 12-bits (0.0625 degree C).
+that are set at device power on to the highest resolution: 12-bits.
+
+One additional note about the ds1721 is that although the data sheet says
+the temperature flags (THF and TLF) are used internally, these flags do
+get set and cleared as the actual temperature crosses the min or max settings.
+
+The DS1631 is also pin compatible with the DS1621 and feature compatible with
+the DS1721, however the DS1631 accuracy is +/- 0.5 degree Celsius over the
+same range.
 
-Changing the DS1721 resolution mode affects the conversion time and can be
+Changing the DS1631/1721 resolution mode affects the conversion time and can be
 done from userspace, via the device 'update_interval' sysfs attribute. This
 attribute will normalize range of input values to the device maximum resolution
 values defined in the datasheet as such:
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 0114ed4b3c07..4f713705d373 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -355,6 +355,7 @@ config SENSORS_DS1621
           Integrated DS1621 sensor chips and compatible models including:
 
           - Dallas Semiconductor DS1625
+          - Maxim Integrated DS1631
           - Maxim Integrated DS1721
 
           This driver can also be built as a module.  If so, the module
diff --git a/drivers/hwmon/ds1621.c b/drivers/hwmon/ds1621.c
index b5d80fb851d0..98adf77fdc84 100644
--- a/drivers/hwmon/ds1621.c
+++ b/drivers/hwmon/ds1621.c
@@ -10,8 +10,8 @@
  * resolution, a thermal alarm output (Tout), and user-defined minimum
  * and maximum temperature thresholds (TH and TL).
  *
- * The DS1625 and DS1721 are pin compatible with the DS1621 and similar
- * in operation, with slight variations as noted in the device
+ * The DS1625, DS1631, and DS1721 are pin compatible with the DS1621 and
+ * similar in operation, with slight variations as noted in the device
  * datasheets (please refer to www.maximintegrated.com for specific
  * device information).
  *
@@ -51,7 +51,7 @@ static const unsigned short normal_i2c[] = { 0x48, 0x49, 0x4a, 0x4b, 0x4c,
                                         0x4d, 0x4e, 0x4f, I2C_CLIENT_END };
 
 /* Supported devices */
-enum chips { ds1621, ds1625, ds1721 };
+enum chips { ds1621, ds1625, ds1631, ds1721 };
 
 /* Insmod parameters */
 static int polarity = -1;
@@ -69,6 +69,10 @@ MODULE_PARM_DESC(polarity, "Output's polarity: 0 = active high, 1 = active low")
  *   7    6    5    4    3    2    1    0
  * |Done|THF |TLF |NVB | 1  | 0  |POL |1SHOT|
  *
+ * - DS1631:
+ *   7    6    5    4    3    2    1    0
+ * |Done|THF |TLF |NVB | R1 | R0 |POL |1SHOT|
+ *
  * - DS1721:
  *   7    6    5    4    3    2    1    0
  * |Done| X  | X  | U  | R1 | R0 |POL |1SHOT|
@@ -139,8 +143,8 @@ static inline int DS1621_TEMP_FROM_REG(u16 reg)
 /*
  * TEMP: 0.001C/bit (-55C to +125C)
  * REG:
- *  - 1621, 1625: x = 0.5C
- *  - 1721:       x = 0.0625C
+ *  - 1621, 1625: 0.5C/bit
+ *  - 1631, 1721: 0.0625C/bit
  * Assume highest resolution and let the bits fall where they may..
  */
 static inline u16 DS1621_TEMP_TO_REG(long temp)
@@ -174,6 +178,7 @@ static void ds1621_init_client(struct i2c_client *client)
                 data->update_interval = DS1625_CONVERSION_MAX;
                 sreg = DS1621_COM_START;
                 break;
+        case ds1631:
         case ds1721:
                 resol = (new_conf & DS1621_REG_CONFIG_RESOL) >>
                          DS1621_REG_CONFIG_RESOL_SHIFT;
@@ -342,7 +347,7 @@ static umode_t ds1621_attribute_visible(struct kobject *kobj,
         struct ds1621_data *data = i2c_get_clientdata(client);
 
         if (attr == &dev_attr_update_interval.attr)
-                if (data->kind != ds1721)
+                if (data->kind == ds1621 || data->kind == ds1625)
                         /* shhh, we're hiding update_interval */
                         return 0;
         return attr->mode;
@@ -376,7 +381,14 @@ static int ds1621_detect(struct i2c_client *client,
         conf = i2c_smbus_read_byte_data(client, DS1621_REG_CONF);
         if (conf < 0 || conf & DS1621_REG_CONFIG_NVB)
                 return -ENODEV;
-        /* The 7 lowest bits of a temperature should always be 0. */
+        /*
+         * The ds1621 & ds1625 use 9-bit resolution, so the 7 lowest bits
+         * of the temperature should always be 0 (NOTE: The other chips
+         * have multi-resolution support, so if they have 9-bit resolution
+         * configured and the min/max temperature values set accordingly,
+         * then if not explicitly instantiated, they *will* appear as and
+         * emulate a ds1621 device).
+         */
         for (i = 0; i < ARRAY_SIZE(DS1621_REG_TEMP); i++) {
                 temp = i2c_smbus_read_word_data(client, DS1621_REG_TEMP[i]);
                 if (temp < 0 || (temp & 0x7f00))
@@ -438,6 +450,7 @@ static int ds1621_remove(struct i2c_client *client)
 static const struct i2c_device_id ds1621_id[] = {
         { "ds1621", ds1621 },
         { "ds1625", ds1625 },
+        { "ds1631", ds1631 },
         { "ds1721", ds1721 },
         { }
 };