hwmon/coretemp: Add more safety checks

Add detection of AE18 Errata of Core processor and warns
users that the absolute readings might be wrong for Core2 processor.

Signed-off-by: Rudolf Marek <r.marek@assembler.cz>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

1 files changed, 29 insertions, 3 deletions

diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c
index 75e3911810a3..0328382df8fa 100644
--- a/drivers/hwmon/coretemp.c
+++ b/drivers/hwmon/coretemp.c
@@ -176,6 +176,22 @@ static int __devinit coretemp_probe(struct platform_device *pdev)
                 goto exit_free;
         }
 
+        /* Check if we have problem with errata AE18 of Core processors:
+           Readings might stop update when processor visited too deep sleep,
+           fixed for stepping D0 (6EC).
+        */
+
+        if ((c->x86_model == 0xe) && (c->x86_mask < 0xc)) {
+                /* check for microcode update */
+                rdmsr_on_cpu(data->id, MSR_IA32_UCODE_REV, &eax, &edx);
+                if (edx < 0x39) {
+                        dev_err(&pdev->dev,
+                                "Errata AE18 not fixed, update BIOS or "
+                                "microcode of the CPU!\n");
+                        goto exit_free;
+                }
+        }
+
         /* Some processors have Tjmax 85 following magic should detect it
            Intel won't disclose the information without signed NDA, but
            individuals cannot sign it. Catch(ed) 22.
@@ -193,6 +209,19 @@ static int __devinit coretemp_probe(struct platform_device *pdev)
                 }
         }
 
+        /* Intel says that above should not work for desktop Core2 processors,
+           but it seems to work. There is no other way how get the absolute
+           readings. Warn the user about this. First check if are desktop,
+           bit 50 of MSR_IA32_PLATFORM_ID should be 0.
+        */
+
+        rdmsr_safe_on_cpu(data->id, MSR_IA32_PLATFORM_ID, &eax, &edx);
+
+        if ((c->x86_model == 0xf) && (!(edx & 0x00040000))) {
+                dev_warn(&pdev->dev, "Using undocumented features, absolute "
+                         "temperature might be wrong!\n");
+        }
+
         platform_set_drvdata(pdev, data);
 
         if ((err = sysfs_create_group(&pdev->dev.kobj, &coretemp_group)))
@@ -330,9 +359,6 @@ static int __init coretemp_init(void)
         int i, err = -ENODEV;
         struct pdev_entry *p, *n;
 
-        printk(KERN_NOTICE DRVNAME ": This driver uses undocumented features "
-                "of Core CPU. Temperature might be wrong!\n");
-
         /* quick check if we run Intel */
         if (cpu_data[0].x86_vendor != X86_VENDOR_INTEL)
                 goto exit;