[ltp] [patch 07/12][2.6.18] ibm-acpi: document fan control
Henrique de Moraes Holschuh
linux-thinkpad@linux-thinkpad.org
Mon, 23 Oct 2006 12:17:52 -0300
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: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Cc: borislav@users.sourceforge.net
---
drivers/acpi/ibm_acpi.c | 107 +++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 105 insertions(+), 2 deletions(-)
Index: 2.6.18/drivers/acpi/ibm_acpi.c
===================================================================
--- 2.6.18.orig/drivers/acpi/ibm_acpi.c
+++ 2.6.18/drivers/acpi/ibm_acpi.c
@@ -204,7 +204,7 @@ 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 */
@@ -225,6 +225,103 @@ enum thermal_access_mode {
IBMACPI_THERMAL_TPEC_16, /* Use ACPI EC regs, 16 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. Disables
+ * tachometer, and speeds up fan to 100% duty-cycle,
+ * which speeds it up FAR above the standard RPM
+ * levels. May damage the hardware.
+ * 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.
+ *
+ * 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, but its 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.
+ */
+
enum fan_status_access_mode {
IBMACPI_FAN_NONE = 0, /* No fan status or control */
IBMACPI_FAN_RD_ACPI_GFAN, /* Use ACPI GFAN */
@@ -1671,7 +1768,7 @@ 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 |= IBMACPI_FAN_CMD_SPEED | IBMACPI_FAN_CMD_ENABLE;
} else {
@@ -1689,6 +1786,9 @@ static int fan_read(char *p)
int len = 0;
u8 lo, hi, status;
+ /* TODO:
+ * Add IBMACPI_FAN_RD_ACPI_FANS ? */
+
switch (fan_status_access_mode) {
case IBMACPI_FAN_RD_ACPI_GFAN:
/* 570, 600e/x, 770e, 770x */
@@ -1844,6 +1944,9 @@ static int fan_write_cmd_speed(const cha
{
int speed;
+ /* TODO:
+ * Support speed <low> <medium> <high> ? */
+
if (sscanf(cmd, "speed %d", &speed) != 1)
return 0;
--
"One disk to rule them all, One disk to find them. One disk to bring
them all and in the darkness grind them. In the Land of Redmond
where the shadows lie." -- The Silicon Valley Tarot
Henrique Holschuh