Patch for controlling fan speed

Overview

This patch extends the ibm-acpi Linux kernel module to control fan speed. It can be used to reduce fan noise and power consumption.

When this patch is applied and the ibm-acpi module is loaded with the experimental=1 module parameter, the following new capabilities are added to /proc/acpi/ibm/fan:

• # echo LEVEL > /proc/acpi/ibm/fan sets a fan speed level between 0 and 7, where LEVEL=0 means fan off and LEVEL=7 is the fastest speed.
• # echo auto > /proc/acpi/ibm/fan tells the embedded controller to set the fan speed automatically according to system temperatures (this is the default).
• # cat /proc/acpi/ibm/fan shows the current fan level (in addition to the fan speed in RPM).

This patch is best used with a program that monitors system temperature and sets the fan speed accordingly. The current scripts for fan control could serve as the basis of such program.

ATTENTION!

Overriding the system's automatic temperature control may cause permanent hardware damage. Even when using temperature monitoring software, it is not clear whether the software can access all temperature sensor accessible to the embedded controller and understand them correctly. Moreover, this patch relies on an undocumented hardware interface, and may thus have arbitrary effects (especially on models it wasn't tested on).

Models on which this patch works

• ThinkPad T43, T43p
  (levels 1-2 = ~3300RPM, level 3-5 = ~4100RPM, level 6-7 = ~4700 RPM)

Probably many other models; please update this page with your results.

I can confirm that it works on Thinkpad T43 here. However after applying the patch, the fan speed monitor of gkrellm 2.2.7 cannot read value correctly. Maybe we gkrellm is reading the second line for speed but instead find the line for level, so it got confused? Would it be possible to interchange the lines so that speed still appears in the second line and level appears in the third instead? I'm no coder, just a suggestion to improve the patch. --Jiang

Models on which this patch doesn't work

• ThinkPad 560, 600E, 600X, 770E, 770X (these use a different fan control interface)

The patch

This also includes a minor fix (rename of device_add) to make ibm-acpi 0.11 compile on kernel 2.6.13.

--- ibm-acpi-0.11-orig/ibm_acpi.c	2005-03-17 12:06:16.000000000 +0200
+++ ibm-acpi-0.11/ibm_acpi.c	2005-10-24 12:56:44.000000000 +0200
@@ -1488,11 +1488,16 @@ static int fan_read(char *p)
 	} else {
 		/* all except 570, 600e/x, 770e, 770x */
 		if (!acpi_ec_read(fan_status_offset, &status))
 			len += sprintf(p + len, "status:\t\tunreadable\n");
-		else
+		else {
 			len += sprintf(p + len, "status:\t\t%s\n",
-				       enabled(status, 7));
+				       status ? "enabled" : "disabled");
+			if (status & 0x80)
+				len += sprintf(p + len, "level:\t\tauto\n");
+			else
+				len += sprintf(p + len, "level:\t\t%d\n", status);
+		}
 
 		if (!acpi_ec_read(fan_rpm_offset,     &lo) ||
 		    !acpi_ec_read(fan_rpm_offset + 1, &hi))
 			len += sprintf(p + len, "speed:\t\tunreadable\n");
@@ -1506,9 +1511,10 @@ static int fan_read(char *p)
 		len += sprintf(p + len, "commands:\tlevel <level>"
 			       " (<level> is 0-7)\n");
 	if (!gfan_handle)
 		/* all except 570, 600e/x, 770e, 770x */
-		len += sprintf(p + len, "commands:\tenable, disable\n");
+		len += sprintf(p + len, "commands:\tenable, disable, level <level>\n"
+			                "         \t(<level> is 0-7 or auto)\n");
 	if (fans_handle)
 		/* X31, X40 */
 		len += sprintf(p + len, "commands:\tspeed <speed>"
 			       " (<speed> is 0-65535)\n");
@@ -1528,17 +1534,24 @@ static int fan_write(char *buf)
 			/* 570, 770x-JL */
 			if (!acpi_evalf(sfan_handle, NULL, NULL, "vd", level))
 				return -EIO;
 		} else if (!gfan_handle &&
-			   strlencmp(cmd, "enable") == 0) {
+			   ( (strlencmp(cmd, "enable") == 0) ||
+			     (strlencmp(cmd, "level auto") == 0) ) ) {
 			/* all except 570, 600e/x, 770e, 770x */
 			if (!acpi_ec_write(fan_status_offset, 0x80))
 				return -EIO;
 		} else if (!gfan_handle &&
 			   strlencmp(cmd, "disable") == 0) {
 			/* all except 570, 600e/x, 770e, 770x */
 			if (!acpi_ec_write(fan_status_offset, 0x00))
 				return -EIO;
+		} else if (!gfan_handle &&
+		    sscanf(cmd, "level %d", &level) == 1 &&
+		    level >=0 && level <= 7) {
+			/* all except 570, 600e/x, 770e, 770x */
+			if (!acpi_ec_write(fan_status_offset, level))
+				return -EIO;
 		} else if (fans_handle &&
 		    sscanf(cmd, "speed %d", &speed) == 1 &&
 		    speed >= 0 && speed <= 65535) {
 			/* X31, X40 */
@@ -1751,9 +1764,9 @@ static int __init setup_notify(struct ib
 
 	return 0;
 }
 
-static int device_add(struct acpi_device *device)
+static int ibmacpi_device_add(struct acpi_device *device)
 {
 	return 0;
 }
 
@@ -1769,9 +1782,9 @@ static int __init register_driver(struct
 
 	memset(ibm->driver, 0, sizeof(struct acpi_driver));
 	sprintf(ibm->driver->name, "%s/%s", IBM_NAME, ibm->name);
 	ibm->driver->ids = ibm->hid;
-	ibm->driver->ops.add = &device_add;
+	ibm->driver->ops.add = &ibmacpi_device_add;
 
 	ret = acpi_bus_register_driver(ibm->driver);
 	if (ret < 0) {
 		printk(IBM_ERR "acpi_bus_register_driver(%s) failed: %d\n",

Hardware spec

The patch relies on the following hardware behavior, discovered experimentally on a ThinkPad T43.

 ACPI DSDT register _SB.PCI0.LPC.EC.HFSP (8 bits, offset 0x2F in the EmbeddedController address space):

 7 6 5 4 3 2 1 0
 | ? ? |   \___/
 |     |     |
 |     |     +------ manual fan speed level (0=disable, 1=min, ..., 7=max)
 |     \------------ no effect
 \------------------ automatic fan speed control (1=enable, overrides manual)