hwmon: (k8temp) fix temperature reporting

Current Temperature for K8 RevG desktop CPUs is a "normalized value" which can be below ambient temperature.

As a consequence lots of RevG systems report temperatures like:

sensors
k8temp-pci-00c3
Adapter: PCI adapter
Core0 Temp:

              +17C
 Core0 Temp:
               +3C
 Core1 Temp:
              +21C
 Core1 Temp:
               +5C

being quite below ambient temperature.
There are even reports of negative temperature values.

This patch corrects the temperature reporting of k8temp for RevG desktop CPUs.

Cc Rudolf Marek <[email protected]>

Signed-off-by Andreas Herrmann <[email protected]>

---
 drivers/hwmon/k8temp.c |   17 +++++++++++++++--
 1 files changed, 15 insertions(+), 2 deletions(-)

drivers/hwmon/k8temp.c +5 -2

index ff12281..b138f79 100644
@@ -49,6 +49,7 @@ struct k8temp_data {
 	u8 sensorsp;		/* sensor presence bits - SEL_CORE & SEL_PLACE */
 	u32 temp[2][2];		/* core, place */
 	u8 swap_core_select;    /* meaning of SEL_CORE is inverted */
+	u32 temp_offset;
 };
 
 static struct k8temp_data *k8temp_update_device(struct device *dev)

@@ -116,13 +117,15 @@ static ssize_t show_temp(struct device *dev,
 	    to_sensor_dev_attr_2(devattr);
 	int core = attr->nr;
 	int place = attr->index;
+	int temp;
 	struct k8temp_data *data = k8temp_update_device(dev);
 
 	if (data->swap_core_select)
 		core = core ? 0 : 1;
 
-	return sprintf(buf, "%d\n",
-		       TEMP_FROM_REG(data->temp[core][place]));
+	temp = TEMP_FROM_REG(data->temp[core][place]) + data->temp_offset;
+
+	return sprintf(buf, "%d\n", temp);
 }
 
 /* core, place */

drivers/hwmon/k8temp.c +1 -0

+
 		break;
 	}
 

drivers/hwmon/k8temp.c static int __devinit k8temp_probe(struct pci_dev *pdev, · line 184

Quoted 7 lines

drivers/hwmon/k8temp.c +3 -0

@@ -176,6 +179,16 @@ static int __devinit k8temp_probe(struct pci_dev *pdev,
 				 "wrong - check erratum #141\n");
 		}
 
+		if (((model >= 0x68) && (model != 0xc1)) &&
+		    !(model = 0x68) && !(model = 0x6c) &&
+		    !(model = 0x7c))

This test is pretty confusing, with these extra parentheses and the mix of (a != b) and !(a = b). What about the following instead? As far as I can see, it leads to the same results, but is much more readable:

		if (model >= 0x69 &&
		    !(model = 0xc1 || model = 0x6c || model = 0x7c))

drivers/hwmon/k8temp.c static int __devinit k8temp_probe(struct pci_dev *pdev, · line 190

Quoted 6 lines

drivers/hwmon/k8temp.c +6 -0

+			/*
+			 * RevG desktop CPUs (i.e. no socket S1G1 parts)
+			 * need additional offset, otherwise reported
+			 * temperature is below ambient temperature
+			 */
+			data->temp_offset = 21000;

If you apply the same offset to all sensors, you'll still obtain something odd:

k8temp-pci-00c3
Adapter: PCI adapter
Core0 Temp:

              +38°C
 Core0 Temp:
              +24°C
 Core1 Temp:
              +42°C
 Core1 Temp:
              +26°C

That's not terribly realistic, is it? Unless both sensors for a given core are very far apart -
but I suspect each core is pretty small,
isn't it?

Quoted 14 lines · Jean Delvare

If you apply the same offset to all sensors, you'll still obtain something odd:

k8temp-pci-00c3
Adapter: PCI adapter
Core0 Temp:

              +38°C
 Core0 Temp:
              +24°C
 Core1 Temp:
              +42°C
 Core1 Temp:
              +26°C

Quoted 4 lines

That's not terribly realistic, is it? Unless both sensors for a given core are very far apart -
but I suspect each core is pretty small,
isn't it?

"Far" is relative, isn't it ;-)

Guess this is from an idle system.
Please bring load on both cores and look at the temperature differences again.