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

Commit a8b7a662 authored by Henrique de Moraes Holschuh's avatar Henrique de Moraes Holschuh Committed by Len Brown
Browse files

ACPI: ibm-acpi: document fan control 

This patch documents the ThinkPad fan control strategies.  Source of the
data:

0. ibm-acpi source
1. DSDTs for various ThinkPads (770, X31, X40, X41, T43, A21m, T22)
2. http://thinkwiki.org/wiki/Embedded_Controller_Firmware#Firmware_Issues
3. http://thinkwiki.org/wiki/How_to_control_fan_speed


4. Various threads about windows fan control utilities in thinkpads.com

Signed-off-by: default avatarHenrique de Moraes Holschuh <hmh@hmh.eng.br>
parent 18ad7996

drivers/acpi/ibm_acpi.c

+108 −2
Original line number Diff line number Diff line
@@ -205,7 +205,7 @@ IBM_HANDLE(led, ec, "SLED", /* 570 */ 
IBM_HANDLE(beep, ec, "BEEP");	/* all except R30, R31 */

IBM_HANDLE(ecrd, ec, "ECRD");	/* 570 */

IBM_HANDLE(ecwr, ec, "ECWR");	/* 570 */

IBM_HANDLE(fans, ec, "FANS");	/* X31, X40 */

IBM_HANDLE(fans, ec, "FANS");	/* X31, X40, X41 */



IBM_HANDLE(gfan, ec, "GFAN",	/* 570 */

	   "\\FSPD",		/* 600e/x, 770e, 770x */
@@ -231,6 +231,106 @@ struct ibm_thermal_sensors_struct { 
	s32 temp[IBMACPI_MAX_THERMAL_SENSORS];

};



/*

 * FAN ACCESS MODES

 *

 * IBMACPI_FAN_RD_ACPI_GFAN:

 * 	ACPI GFAN method: returns fan level

 *

 * 	see IBMACPI_FAN_WR_ACPI_SFAN

 * 	EC 0x2f not available if GFAN exists

 *

 * IBMACPI_FAN_WR_ACPI_SFAN:

 * 	ACPI SFAN method: sets fan level, 0 (stop) to 7 (max)

 *

 * 	EC 0x2f might be available *for reading*, but never for writing.

 *

 * IBMACPI_FAN_WR_TPEC:

 * 	ThinkPad EC register 0x2f (HFSP): fan control loop mode Supported

 * 	on almost all ThinkPads

 *

 * 	Fan speed changes of any sort (including those caused by the

 * 	disengaged mode) are usually done slowly by the firmware as the

 * 	maximum ammount of fan duty cycle change per second seems to be

 * 	limited.

 *

 * 	Reading is not available if GFAN exists.

 * 	Writing is not available if SFAN exists.

 *

 * 	Bits

 *	 7	automatic mode engaged;

 *  		(default operation mode of the ThinkPad)

 * 		fan level is ignored in this mode.

 *	 6	disengage mode (takes precedence over bit 7);

 *		not available on all thinkpads.  May disable

 *		the tachometer, and speeds up fan to 100% duty-cycle,

 *		which speeds it up far above the standard RPM

 *		levels.  It is not impossible that it could cause

 *		hardware damage.

 *	5-3	unused in some models.  Extra bits for fan level

 *		in others, but still useless as all values above

 *		7 map to the same speed as level 7 in these models.

 *	2-0	fan level (0..7 usually)

 *			0x00 = stop

 * 			0x07 = max (set when temperatures critical)

 * 		Some ThinkPads may have other levels, see

 * 		IBMACPI_FAN_WR_ACPI_FANS (X31/X40/X41)

 *

 *	FIRMWARE BUG: on some models, EC 0x2f might not be initialized at

 *	boot. Apparently the EC does not intialize it, so unless ACPI DSDT

 *	does so, its initial value is meaningless (0x07).

 *

 *	For firmware bugs, refer to:

 *	http://thinkwiki.org/wiki/Embedded_Controller_Firmware#Firmware_Issues

 *

 * 	----

 *

 *	ThinkPad EC register 0x84 (LSB), 0x85 (MSB):

 *	Main fan tachometer reading (in RPM)

 *

 *	This register is present on all ThinkPads with a new-style EC, and

 *	it is known not to be present on the A21m/e, and T22, as there is

 *	something else in offset 0x84 according to the ACPI DSDT.  Other

 *	ThinkPads from this same time period (and earlier) probably lack the

 *	tachometer as well.

 *

 *	Unfortunately a lot of ThinkPads with new-style ECs but whose firwmare

 *	was never fixed by IBM to report the EC firmware version string

 *	probably support the tachometer (like the early X models), so

 *	detecting it is quite hard.  We need more data to know for sure.

 *

 *	FIRMWARE BUG: always read 0x84 first, otherwise incorrect readings

 *	might result.

 *

 *	FIRMWARE BUG: when EC 0x2f bit 6 is set (disengaged mode), this

 *	register is not invalidated in ThinkPads that disable tachometer

 *	readings.  Thus, the tachometer readings go stale.

 *

 *	For firmware bugs, refer to:

 *	http://thinkwiki.org/wiki/Embedded_Controller_Firmware#Firmware_Issues

 *

 * IBMACPI_FAN_WR_ACPI_FANS:

 *	ThinkPad X31, X40, X41.  Not available in the X60.

 *

 *	FANS ACPI handle: takes three arguments: low speed, medium speed,

 *	high speed.  ACPI DSDT seems to map these three speeds to levels

 *	as follows: STOP LOW LOW MED MED HIGH HIGH HIGH HIGH

 *	(this map is stored on FAN0..FAN8 as "0,1,1,2,2,3,3,3,3")

 *

 * 	The speeds are stored on handles

 * 	(FANA:FAN9), (FANC:FANB), (FANE:FAND).

 *

 * 	There are three default speed sets, acessible as handles:

 * 	FS1L,FS1M,FS1H; FS2L,FS2M,FS2H; FS3L,FS3M,FS3H

 *

 * 	ACPI DSDT switches which set is in use depending on various

 * 	factors.

 *

 * 	IBMACPI_FAN_WR_TPEC is also available and should be used to

 * 	command the fan.  The X31/X40/X41 seems to have 8 fan levels,

 * 	but the ACPI tables just mention level 7.

 */



enum fan_status_access_mode {

	IBMACPI_FAN_NONE = 0,		/* No fan status or control */

	IBMACPI_FAN_RD_ACPI_GFAN,	/* Use ACPI GFAN */
@@ -1722,7 +1822,7 @@ static int fan_init(void) 
			/* all other models implement TP EC 0x2f control */



			if (fans_handle) {

				/* X31, X40 */

				/* X31, X40, X41 */

				fan_control_access_mode =

				    IBMACPI_FAN_WR_ACPI_FANS;

				fan_control_commands |=
@@ -1742,6 +1842,9 @@ static int fan_get_status(u8 *status) 
{

	u8 s;



	/* TODO:

	 * Add IBMACPI_FAN_RD_ACPI_FANS ? */



	switch (fan_status_access_mode) {

	case IBMACPI_FAN_RD_ACPI_GFAN:

		/* 570, 600e/x, 770e, 770x */
@@ -1950,6 +2053,9 @@ static int fan_write_cmd_speed(const char *cmd, int *rc) 
{

	int speed;



	/* TODO:

	 * Support speed <low> <medium> <high> ? */



	if (sscanf(cmd, "speed %d", &speed) != 1)

		return 0;