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>

1 files changed, 57 insertions, 23 deletions

diff --git a/drivers/hwmon/w83795.c b/drivers/hwmon/w83795.c
index c7f6b1fd0899..6596303566e1 100644
--- 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;
 }