1 files changed, 49 insertions, 4 deletions

diff --git a/drivers/acpi/ibm_acpi.c b/drivers/acpi/ibm_acpi.c
index 3c091c4b461f..56743c5a0439 100644
--- a/drivers/acpi/ibm_acpi.c
+++ b/drivers/acpi/ibm_acpi.c
@@ -362,7 +362,7 @@ enum {					/* Fan control constants */
                                                  * control */
 };
 
-static char* ibm_thinkpad_ec_found = NULL;
+static char *ibm_thinkpad_ec_found = NULL;
 
 struct ibm_struct {
         char *name;
@@ -1794,13 +1794,15 @@ static enum fan_status_access_mode fan_status_access_mode;
 static enum fan_control_access_mode fan_control_access_mode;
 static enum fan_control_commands fan_control_commands;
 
+static int fan_control_status_known;
+static u8 fan_control_initial_status;
+
 static int fan_init(void)
 {
-        u8 status;
-
         fan_status_access_mode = IBMACPI_FAN_NONE;
         fan_control_access_mode = IBMACPI_FAN_WR_NONE;
         fan_control_commands = 0;
+        fan_control_status_known = 1;
 
         if (gfan_handle) {
                 /* 570, 600e/x, 770e, 770x */
@@ -1808,8 +1810,33 @@ static int fan_init(void)
         } else {
                 /* all other ThinkPads: note that even old-style
                  * ThinkPad ECs supports the fan control register */
-                if (likely(acpi_ec_read(fan_status_offset, &status))) {
+                if (likely(acpi_ec_read(fan_status_offset,
+                                        &fan_control_initial_status))) {
                         fan_status_access_mode = IBMACPI_FAN_RD_TPEC;
+
+                        /* In some ThinkPads, neither the EC nor the ACPI
+                         * DSDT initialize the fan status, and it ends up
+                         * being set to 0x07 when it *could* be either
+                         * 0x07 or 0x80.
+                         *
+                         * Enable for TP-1Y (T43), TP-78 (R51e),
+                         * TP-76 (R52), TP-70 (T43, R52), which are known
+                         * to be buggy. */
+                        if (fan_control_initial_status == 0x07 &&
+                            ibm_thinkpad_ec_found &&
+                            ((ibm_thinkpad_ec_found[0] == '1' &&
+                              ibm_thinkpad_ec_found[1] == 'Y') ||
+                             (ibm_thinkpad_ec_found[0] == '7' &&
+                              (ibm_thinkpad_ec_found[1] == '6' ||
+                               ibm_thinkpad_ec_found[1] == '8' ||
+                               ibm_thinkpad_ec_found[1] == '0'))
+                            )) {
+                                printk(IBM_NOTICE
+                                       "fan_init: initial fan status is "
+                                       "unknown, assuming it is in auto "
+                                       "mode\n");
+                                fan_control_status_known = 0;
+                        }
                 } else {
                         printk(IBM_ERR
                                "ThinkPad ACPI EC access misbehaving, "
@@ -1930,9 +1957,21 @@ static int fan_read(char *p)
                 if ((rc = fan_get_status(&status)) < 0)
                         return rc;
 
+                if (unlikely(!fan_control_status_known)) {
+                        if (status != fan_control_initial_status)
+                                fan_control_status_known = 1;
+                        else
+                                /* Return most likely status. In fact, it
+                                 * might be the only possible status */
+                                status = IBMACPI_FAN_EC_AUTO;
+                }
+
                 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;
 
@@ -1997,6 +2036,8 @@ static int fan_set_level(int level)
 
                 if (!acpi_ec_write(fan_status_offset, level))
                         return -EIO;
+                else
+                        fan_control_status_known = 1;
                 break;
 
         default:
@@ -2022,6 +2063,8 @@ static int fan_set_enable(void)
 
                 if (!acpi_ec_write(fan_status_offset, s))
                         return -EIO;
+                else
+                        fan_control_status_known = 1;
                 break;
 
         case IBMACPI_FAN_WR_ACPI_SFAN:
@@ -2051,6 +2094,8 @@ static int fan_set_disable(void)
         case IBMACPI_FAN_WR_TPEC:
                 if (!acpi_ec_write(fan_status_offset, 0x00))
                         return -EIO;
+                else
+                        fan_control_status_known = 1;
                 break;
 
         case IBMACPI_FAN_WR_ACPI_SFAN: