On old CPUs (and even some recent Atom CPUs) TjMax can't be read from
the CPU registers, so it is guessed by the driver using a complex
heuristic which isn't reliable. So let users who know their CPU's
TjMax pass it as a module parameter.
Signed-off-by: Jean Delvare <khali@xxxxxxxxxxxx>
Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Cc: "R, Durgadoss" <durgadoss.r@xxxxxxxxx>
Cc: Guenter Roeck <guenter.roeck@xxxxxxxxxxxx>
Cc: Alexander Stein <alexander.stein@xxxxxxxxxxxxxxxxxxxxx>
---
Documentation/hwmon/coretemp | 7 ++++---
drivers/hwmon/coretemp.c | 15 +++++++++++++++
2 files changed, 19 insertions(+), 3 deletions(-)
--- linux-3.1-rc4.orig/drivers/hwmon/coretemp.c 2011-09-15 14:50:46.000000000 +0200
+++ linux-3.1-rc4/drivers/hwmon/coretemp.c 2011-09-16 18:35:18.000000000 +0200
@@ -36,11 +36,20 @@
#include <linux/cpu.h>
#include <linux/pci.h>
#include <linux/smp.h>
+#include <linux/moduleparam.h>
#include <asm/msr.h>
#include <asm/processor.h>
#define DRVNAME "coretemp"
+/*
+ * force_tjmax only matters when TjMax can't be read from the CPU itself.
+ * When set, it replaces the driver's suboptimal heuristic.
+ */
+static int force_tjmax;
+module_param_named(tjmax, force_tjmax, int, 0444);
+MODULE_PARM_DESC(tjmax, "TjMax value in degrees Celsius");
+
#define BASE_SYSFS_ATTR_NO 2 /* Sysfs Base attr no for coretemp */
#define NUM_REAL_CORES 16 /* Number of Real cores per cpu */
#define CORETEMP_NAME_LENGTH 17 /* String Length of attrs */
@@ -398,6 +407,12 @@ static int get_tjmax(struct cpuinfo_x86
}
}
+ if (force_tjmax) {
+ dev_notice(dev, "TjMax forced to %d degrees C by user\n",
+ force_tjmax);
+ return force_tjmax * 1000;
+ }
+
/*
* An assumption is made for early CPUs and unreadable MSR.
* NOTE: the calculated value may not be correct.
--- linux-3.1-rc4.orig/Documentation/hwmon/coretemp 2011-08-16 11:49:35.000000000 +0200
+++ linux-3.1-rc4/Documentation/hwmon/coretemp 2011-09-16 18:26:19.000000000 +0200
@@ -49,9 +49,10 @@ tempX_label - Contains string "Core X",
number. For Package temp, this will be "Physical id Y",
where Y is the package number.
-The TjMax temperature is set to 85 degrees C if undocumented model specific
-register (UMSR) 0xee has bit 30 set. If not the TjMax is 100 degrees C as
-(sometimes) documented in processor datasheet.
+On CPU models which support it, TjMax is read from a model-specific register.
+On other models, it is set to an arbitrary value based on weak heuristics.
+If these heuristics don't work for you, you can pass the correct TjMax value
+as a module parameter (tjmax).
Appendix A. Known TjMax lists (TBD):
Some information comes from ark.intel.com
--
Jean Delvare
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