--- /tmp/apm.c.orig	Sat Dec 22 15:19:42 2001
+++ /tmp/apm.c	Sat Dec 22 15:17:23 2001
@@ -341,6 +341,11 @@
 #define APM_BIOS_MAGIC		0x4101
 
 /*
+ * idle percentage above which bios idle calls are done
+ */
+#define BIOS_IDLE_TRIGGER	95
+
+/*
  * Local variables
  */
 static struct {
@@ -349,6 +354,8 @@
 }				apm_bios_entry;
 #ifdef CONFIG_APM_CPU_IDLE
 static int			clock_slowed;
+static int			idle_enabled = 1;
+static int			idle_threshold = BIOS_IDLE_TRIGGER;
 #endif
 static int			suspends_pending;
 static int			standbys_pending;
@@ -735,63 +742,84 @@
 	}
 }
 
-#if 0
-extern int hlt_counter;
-
 /*
- * If no process has been interested in this
- * CPU for some time, we want to wake up the
- * power management thread - we probably want
+ * If no process has really been interested in
+ * CPU for some time, we want to call BIOS
+ * power management - we probably want
  * to conserve power.
  */
 #define HARD_IDLE_TIMEOUT (HZ/3)
+#define IDLE_CALC_LIMIT   (HZ*100)
+#define IDLE_LEAKY_MAX    16
 
-/* This should wake up kapmd and ask it to slow the CPU */
-#define powermanagement_idle()  do { } while (0)
+static void (*sys_idle)(void);
+static unsigned int last_jiffies = 0;
+static unsigned int last_stime = 0;
+static int use_apm_idle = 0;
 
 /**
  * apm_cpu_idle		-	cpu idling for APM capable Linux
  *
  * This is the idling function the kernel executes when APM is available. It 
- * tries to save processor time directly by using hlt instructions. A
- * separate apm thread tries to do the BIOS power management.
- *
- * N.B. This is curently not used for kernels 2.4.x.
+ * tries to do BIOS powermanagement based on the average system idle time.
+ * Furthermore it calls the system default idle routine.
  */
 
 static void apm_cpu_idle(void)
 {
-	unsigned int start_idle;
-
-	start_idle = jiffies;
-	while (1) {
-		if (!current->need_resched) {
-			if (jiffies - start_idle < HARD_IDLE_TIMEOUT) {
-				if (!current_cpu_data.hlt_works_ok)
-					continue;
-				if (hlt_counter)
+	int apm_is_idle = 0;
+	unsigned int t1 = jiffies - last_jiffies;
+	unsigned int t2;
+
+recalc:	if(t1 > IDLE_CALC_LIMIT)
+		goto reset;
+
+	if(t1 > HARD_IDLE_TIMEOUT) {
+		t2 = current->times.tms_stime - last_stime;
+		t2 *= 100;
+		t2 /= t1;
+		if (t2 > idle_threshold)
+			use_apm_idle = 1;
+		else
+reset:			use_apm_idle = 0;
+		last_jiffies = jiffies;
+		last_stime = current->times.tms_stime;
+	}
+
+	t2 = IDLE_LEAKY_MAX;
+
+	while (!current->need_resched) {
+		if(use_apm_idle) {
+			t1 = jiffies;
+			switch (apm_do_idle()) {
+			case 0:	apm_is_idle = 1;
+				if (t1 != jiffies) {
+					if (t2) {
+						t2 = IDLE_LEAKY_MAX;
+						continue;
+					}
+				} else if (t2) {
+					t2--;
 					continue;
-				__cli();
-				if (!current->need_resched)
-					safe_halt();
-				else
-					__sti();
-				continue;
+				}
+				break;
+			case 1:	apm_is_idle = 1;
+				break;
 			}
-
-			/*
-			 * Ok, do some power management - we've been idle for too long
-			 */
-			powermanagement_idle();
 		}
 
-		schedule();
-		check_pgt_cache();
-		start_idle = jiffies;
+		if (sys_idle)
+			sys_idle();
+
+		t1 = jiffies - last_jiffies;
+		if (t1 > HARD_IDLE_TIMEOUT)
+			goto recalc;
 	}
+
+	if (apm_is_idle)
+		apm_do_busy();
 }
 #endif
-#endif
 
 #ifdef CONFIG_SMP
 static int apm_magic(void * unused)
@@ -1346,17 +1374,12 @@
 
 static void apm_mainloop(void)
 {
-	int timeout = HZ;
 	DECLARE_WAITQUEUE(wait, current);
 
 	add_wait_queue(&apm_waitqueue, &wait);
 	set_current_state(TASK_INTERRUPTIBLE);
 	for (;;) {
-		/* Nothing to do, just sleep for the timeout */
-		timeout = 2 * timeout;
-		if (timeout > APM_CHECK_TIMEOUT)
-			timeout = APM_CHECK_TIMEOUT;
-		schedule_timeout(timeout);
+		schedule_timeout(APM_CHECK_TIMEOUT);
 		if (exit_kapmd)
 			break;
 
@@ -1366,34 +1389,6 @@
 		 */
 		set_current_state(TASK_INTERRUPTIBLE);
 		apm_event_handler();
-#ifdef CONFIG_APM_CPU_IDLE
-		if (!system_idle())
-			continue;
-		
-		/*
-		 *	If we can idle...
-		 */
-		if (apm_do_idle() != -1) {
-			unsigned long start = jiffies;
-			while ((!exit_kapmd) && system_idle()) {
-				if (apm_do_idle()) {
-					set_current_state(TASK_INTERRUPTIBLE);
-					/* APM needs us to snooze .. either
-					   the BIOS call failed (-1) or it
-					   slowed the clock (1). We sleep
-					   until it talks to us again */
-					schedule_timeout(1);
-				}
-				if ((jiffies - start) > APM_CHECK_TIMEOUT) {
-					apm_event_handler();
-					start = jiffies;
-				}
-			}
-			apm_do_busy();
-			apm_event_handler();
-			timeout = 1;
-		}
-#endif
 	}
 	remove_wait_queue(&apm_waitqueue, &wait);
 }
@@ -1814,6 +1809,17 @@
 		if ((strncmp(str, "realmode-power-off", 18) == 0) ||
 		    (strncmp(str, "realmode_power_off", 18) == 0))
 			apm_info.realmode_power_off = !invert;
+#ifdef CONFIG_APM_CPU_IDLE
+		if ((strncmp(str, "apm-idle", 8) == 0) ||
+		    (strncmp(str, "apm_idle", 8) == 0))
+			idle_enabled = !invert;
+		if ((strncmp(str, "apm-idle-threshold=", 19) == 0) ||
+		    (strncmp(str, "apm_idle_threshold=", 19) == 0)) {
+			idle_threshold = simple_strtol(str + 19, NULL, 0);
+			if ( idle_threshold < 0 || idle_threshold > 99 )
+				idle_threshold = BIOS_IDLE_TRIGGER;
+		}
+#endif
 		str = strchr(str, ',');
 		if (str != NULL)
 			str += strspn(str, ", \t");
@@ -1968,6 +1974,13 @@
 
 	misc_register(&apm_device);
 
+#ifdef CONFIG_APM_CPU_IDLE
+	if (idle_enabled) {
+		sys_idle = pm_idle;
+		pm_idle  = apm_cpu_idle;
+	}
+#endif
+
 	return 0;
 }
 
@@ -1975,6 +1988,11 @@
 {
 	int	error;
 
+#ifdef CONFIG_APM_CPU_IDLE
+	if (idle_enabled)
+		pm_idle = sys_idle;
+#endif
+
 	if (((apm_info.bios.flags & APM_BIOS_DISENGAGED) == 0)
 	    && (apm_info.connection_version > 0x0100)) {
 		error = apm_engage_power_management(APM_DEVICE_ALL, 0);
@@ -2012,5 +2030,11 @@
 MODULE_PARM(realmode_power_off, "i");
 MODULE_PARM_DESC(realmode_power_off,
 		"Switch to real mode before powering off");
+#ifdef CONFIG_APM_CPU_IDLE
+MODULE_PARM(apm_idle, "i");
+MODULE_PARM_DESC(apm_idle, "Make BIOS idle calls when idle");
+MODULE_PARM(apm_idle_threshold, "i");
+MODULE_PARM_DESC(apm_idle_threshold, "System idle percentage for BIOS idle call
s");
+#endif
 
 EXPORT_NO_SYMBOLS;