ACPI: thinkpad-acpi: update fan firmware documentation

Update some stuff in the in-code text describing the ThinkPad fan
firmware.  This patch has no code changes.

Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 13 insertions, 15 deletions

diff --git a/drivers/misc/thinkpad_acpi.c b/drivers/misc/thinkpad_acpi.c
index 1683bfe15b35..4131a7875ad7 100644
--- a/drivers/misc/thinkpad_acpi.c
+++ b/drivers/misc/thinkpad_acpi.c
@@ -1852,16 +1852,17 @@ static int volume_write(char *buf)
  *      ACPI GFAN method: returns fan level
  *
  *      see TPACPI_FAN_WR_ACPI_SFAN
- *      EC 0x2f not available if GFAN exists
+ *      EC 0x2f (HFSP) not available if GFAN exists
  *
  * TPACPI_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.
+ *      EC 0x2f (HFSP) might be available *for reading*, but do not use
+ *      it for writing.
  *
  * TPACPI_FAN_WR_TPEC:
- *      ThinkPad EC register 0x2f (HFSP): fan control loop mode Supported
- *      on almost all ThinkPads
+ *      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
@@ -1875,12 +1876,13 @@ static int volume_write(char *buf)
  *       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);
+ *       6      full speed 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.
+ *              the tachometer while the fan controller ramps up
+ *              the speed (which can take up to a few *minutes*).
+ *              Speeds up fan to 100% duty-cycle, which is 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.
@@ -1916,9 +1918,8 @@ static int volume_write(char *buf)
  *      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.
+ *      FIRMWARE BUG: may go stale while the EC is switching to full speed
+ *      mode.
  *
  *      For firmware bugs, refer to:
  *      http://thinkwiki.org/wiki/Embedded_Controller_Firmware#Firmware_Issues
@@ -2283,9 +2284,6 @@ static int fan_read(char *p)
                 len += sprintf(p + len, "status:\t\t%s\n",
                                (status != 0) ? "enabled" : "disabled");
 
-                /* No ThinkPad boots on disengaged mode, we can safely
-                 * assume the tachometer is online if fan control status
-                 * was unknown */
                 if ((rc = fan_get_speed(&speed)) < 0)
                         return rc;