[PATCH] ppc64: Start the FCU in therm_pm72.c

Some G5 recent powermacs start with the fan control unit (FCU) disabled,
by the firmware, causing the thermal control driver to break. We have to
enable it before starting the feedback loops that set the fan speeds.
This patch adds the code to start the FCU.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/macintosh/therm_pm72.c

@@ -317,6 +317,20 @@ static int fan_write_reg(int reg, const unsigned char *ptr, int nb)
 	return nw;
 }
 
+static int start_fcu(void)
+{
+	unsigned char buf = 0xff;
+	int rc;
+
+	rc = fan_write_reg(0xe, &buf, 1);
+	if (rc < 0)
+		return -EIO;
+	rc = fan_write_reg(0x2e, &buf, 1);
+	if (rc < 0)
+		return -EIO;
+	return 0;
+}
+
 static int set_rpm_fan(int fan, int rpm)
 {
 	unsigned char buf[2];
@@ -1011,6 +1025,12 @@ static int main_control_loop(void *x)
 
 	down(&driver_lock);
 
+	if (start_fcu() < 0) {
+		printk(KERN_ERR "kfand: failed to start FCU\n");
+		up(&driver_lock);
+		goto out;
+	}
+
 	/* Set the PCI fan once for now */
 	set_pwm_fan(SLOTS_FAN_PWM_ID, SLOTS_FAN_DEFAULT_PWM);
 
@@ -1057,6 +1077,7 @@ static int main_control_loop(void *x)
 			schedule_timeout(HZ - elapsed);
 	}
 
+ out:
 	DBG("main_control_loop ended\n");
 
 	ctrl_task = 0;