Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit a45a8c85 authored by Jean Delvare's avatar Jean Delvare Committed by Guenter Roeck
Browse files

hwmon: (coretemp) Let the user force TjMax 



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: default avatarJean Delvare <khali@linux-fr.org>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: "R, Durgadoss" <durgadoss.r@intel.com>
Cc: Guenter Roeck <guenter.roeck@ericsson.com>
Cc: Alexander Stein <alexander.stein@systec-electronic.com>
Acked-by: default avatarFenghua Yu <fenghua.yu@intel.com>
Signed-off-by: default avatarGuenter Roeck <guenter.roeck@ericsson.com>
parent 6bf9e9b0

Documentation/hwmon/coretemp

+4 −3
Original line number Diff line number Diff line
@@ -49,9 +49,10 @@ tempX_label - Contains string "Core X", where X is processor 
		   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

drivers/hwmon/coretemp.c

+15 −0
Original line number Diff line number Diff line
@@ -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 *c, u32 id, struct device *dev) 
		}

	}



	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.