hwmon: (k8temp) Bypass core swapping on single-core processors

Commit a2e066bba2 introduced core
swapping for CPU models 64 and later. I recently had a report about
a Sempron 3200+, model 95, for which this patch broke temperature
reading. It happens that this is a single-core processor, so the
effect of the swapping was to read a temperature value for a core
that didn't exist, leading to an incorrect value (-49 degrees C.)

Disabling core swapping on singe-core processors should fix this.

Additional comment from Andreas:

The BKDG says

  Thermal Sensor Core Select (ThermSenseCoreSel)-Bit 2. This bit
  selects the CPU whose temperature is reported in the CurTemp
  field. This bit only applies to dual core processors. For
  single core processors CPU0 Thermal Sensor is always selected.

k8temp_probe() correctly detected that SEL_CORE can't be used on single
core CPU. Thus k8temp did never update the temperature values stored
in temp[1][x] and -49 degrees was reported. For single core CPUs we
must use the values read into temp[0][x].

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Tested-by: Rick Moritz <rhavin@gmx.net>
Acked-by: Andreas Herrmann <andreas.herrmann3@amd.com>
Cc: stable@kernel.org

drivers/hwmon/k8temp.c

@@ -120,7 +120,7 @@ static ssize_t show_temp(struct device *dev,
 	int temp;
 	struct k8temp_data *data = k8temp_update_device(dev);
 
-	if (data->swap_core_select)
+	if (data->swap_core_select && (data->sensorsp & SEL_CORE))
 		core = core ? 0 : 1;
 
 	temp = TEMP_FROM_REG(data->temp[core][place]) + data->temp_offset;