hwmon: (w83795) Improve detection routine

Check for additional identification registers. Improve debugging
messages on failed detection.

Signed-off-by: Jean Delvare <khali@linux-fr.org>

diff --git a/drivers/hwmon/w83795.c b/drivers/hwmon/w83795.c
index c7f6b1fd089905b85cfca818623ff318c00a55ca..6596303566e183a8e603af0c70026e13fad6817f 100644 (file)
--- a/drivers/hwmon/w83795.c
+++ b/drivers/hwmon/w83795.c
@@ -48,6 +48,7 @@ MODULE_PARM_DESC(reset, "Set to 1 to reset chip, not recommended");
 #define W83795_REG_VENDORID            0xfd
 #define W83795_REG_CHIPID              0xfe
 #define W83795_REG_DEVICEID            0xfb
+#define W83795_REG_DEVICEID_A          0xff
 
 #define W83795_REG_I2C_ADDR            0xfc
 #define W83795_REG_CONFIG              0x01
@@ -1684,11 +1685,31 @@ static void w83795_init_client(struct i2c_client *client)
                     w83795_read(client, W83795_REG_CONFIG) | 0x01);
 }
 
+static int w83795_get_device_id(struct i2c_client *client)
+{
+       int device_id;
+
+       device_id = i2c_smbus_read_byte_data(client, W83795_REG_DEVICEID);
+
+       /* Special case for rev. A chips; can't be checked first because later
+          revisions emulate this for compatibility */
+       if (device_id < 0 || (device_id & 0xf0) != 0x50) {
+               int alt_id;
+
+               alt_id = i2c_smbus_read_byte_data(client,
+                                                 W83795_REG_DEVICEID_A);
+               if (alt_id == 0x50)
+                       device_id = alt_id;
+       }
+
+       return device_id;
+}
+
 /* Return 0 if detection is successful, -ENODEV otherwise */
 static int w83795_detect(struct i2c_client *client,
                         struct i2c_board_info *info)
 {
-       u8 tmp, bank;
+       int bank, vendor_id, device_id, expected, i2c_addr, config;
        struct i2c_adapter *adapter = client->adapter;
        unsigned short address = client->addr;
        const char *chip_name;
@@ -1696,32 +1717,44 @@ static int w83795_detect(struct i2c_client *client,
        if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
                return -ENODEV;
        bank = i2c_smbus_read_byte_data(client, W83795_REG_BANKSEL);
+       if (bank < 0 || (bank & 0x7c)) {
+               dev_dbg(&adapter->dev,
+                       "w83795: Detection failed at addr 0x%02hx, check %s\n",
+                       address, "bank");
+               return -ENODEV;
+       }
 
-       tmp = bank & 0x80 ? 0x5c : 0xa3;
        /* Check Nuvoton vendor ID */
-       if (tmp != i2c_smbus_read_byte_data(client,
-                                               W83795_REG_VENDORID)) {
-               pr_debug("w83795: Detection failed at check "
-                        "vendor id\n");
+       vendor_id = i2c_smbus_read_byte_data(client, W83795_REG_VENDORID);
+       expected = bank & 0x80 ? 0x5c : 0xa3;
+       if (vendor_id != expected) {
+               dev_dbg(&adapter->dev,
+                       "w83795: Detection failed at addr 0x%02hx, check %s\n",
+                       address, "vendor id");
                return -ENODEV;
        }
 
-       /* If Nuvoton chip, address of chip and W83795_REG_I2C_ADDR
-          should match */
-       if ((bank & 0x07) == 0
-        && (i2c_smbus_read_byte_data(client, W83795_REG_I2C_ADDR) & 0x7f) !=
-           address) {
-               pr_debug("w83795: Detection failed at check "
-                        "i2c addr\n");
+       /* Check device ID */
+       device_id = w83795_get_device_id(client) |
+                   (i2c_smbus_read_byte_data(client, W83795_REG_CHIPID) << 8);
+       if ((device_id >> 4) != 0x795) {
+               dev_dbg(&adapter->dev,
+                       "w83795: Detection failed at addr 0x%02hx, check %s\n",
+                       address, "device id\n");
                return -ENODEV;
        }
 
-       /* Determine the chip type now */
-       if (0x79 != i2c_smbus_read_byte_data(client,
-                                            W83795_REG_CHIPID)) {
-               pr_debug("w83795: Detection failed at check "
-                        "chip id\n");
-               return -ENODEV;
+       /* If Nuvoton chip, address of chip and W83795_REG_I2C_ADDR
+          should match */
+       if ((bank & 0x07) == 0) {
+               i2c_addr = i2c_smbus_read_byte_data(client,
+                                                   W83795_REG_I2C_ADDR);
+               if ((i2c_addr & 0x7f) != address) {
+                       dev_dbg(&adapter->dev,
+                               "w83795: Detection failed at addr 0x%02hx, "
+                               "check %s\n", address, "i2c addr");
+                       return -ENODEV;
+               }
        }
 
        /* Check 795 chip type: 795G or 795ADG
@@ -1731,14 +1764,15 @@ static int w83795_detect(struct i2c_client *client,
        if ((bank & 0x07) != 0)
                i2c_smbus_write_byte_data(client, W83795_REG_BANKSEL,
                                          bank & ~0x07);
-       if (W83795_REG_CONFIG_CONFIG48 &
-                 i2c_smbus_read_byte_data(client, W83795_REG_CONFIG)) {
+       config = i2c_smbus_read_byte_data(client, W83795_REG_CONFIG);
+       if (config & W83795_REG_CONFIG_CONFIG48)
                chip_name = "w83795adg";
-       } else {
+       else
                chip_name = "w83795g";
-       }
 
        strlcpy(info->type, chip_name, I2C_NAME_SIZE);
+       dev_info(&adapter->dev, "Found %s rev. %c at 0x%02hx\n", chip_name,
+                'A' + (device_id & 0xf), address);
 
        return 0;
 }