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ACPI: thermal: use round_jiffies() when thermal zone polling is enabled

PATCH New Len Brown 1 participant 1 message Sep 4, 2007

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ACPI ACPI thermal driver
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Len Brown

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PATCH 1/1 ACPI: thermal: use round_jiffies() when thermal zone polling is enabled

From: Len Brown <[email protected]>

Properly functioning systems do not use thermal zone polling, they use event-based notification.

However, some users enable periodic thermal zone polling to work around bugs on their platforms, and at least one platform exists with a real _TZP that requests polling.

While thermal zone polling (_TZP) is specified in units to 0.1 seconds, it actually has a maximum granularity of 1 second. Thus, we can safely round up the _TZP timeout to occur on the next 1-second boundary. This will batch it with other 1-second-granularity timers in the system and thus potentially extend processor idle duration.

Note that the same timer is used both for _TZP
and for passive processor thermal throttling.
We can not round up the timeout when it is used
for passive thermal throttling.

Also, we can not make this a deferrable timer,
as temperature is just as relevant during idle
as it is during non-idle.

Signed-off-by Len Brown <[email protected]>
drivers/acpi/thermal.c +8 -5
Index: acpi/drivers/acpi/thermal.c
===================================================================
@@ -711,6 +711,7 @@ static void acpi_thermal_check(void *dat
 	int result = 0;
 	struct acpi_thermal *tz = data;
 	unsigned long sleep_time = 0;
+	unsigned long timeout_jiffies = 0;
 	int i = 0;
 	struct acpi_thermal_state state;
 

@@ -787,10 +788,13 @@ static void acpi_thermal_check(void *dat
 	 * a thermal event occurs).  Note that _TSP and _TZD values are
 	 * given in 1/10th seconds (we must covert to milliseconds).
 	 */
-	if (tz->state.passive)
+	if (tz->state.passive) {
 		sleep_time = tz->trips.passive.tsp * 100;
-	else if (tz->polling_frequency > 0)
+		timeout_jiffies =  jiffies + (HZ * sleep_time) / 1000;
+	} else if (tz->polling_frequency > 0) {
 		sleep_time = tz->polling_frequency * 100;
+		timeout_jiffies =  round_jiffies(jiffies + (HZ * sleep_time) / 1000);
+	}
 
 	ACPI_DEBUG_PRINT((ACPI_DB_INFO, "%s: temperature[%lu] sleep[%lu]\n",
 			  tz->name, tz->temperature, sleep_time));

@@ -804,12 +808,11 @@ static void acpi_thermal_check(void *dat
 			del_timer(&(tz->timer));
 	} else {
 		if (timer_pending(&(tz->timer)))
-			mod_timer(&(tz->timer),
-					jiffies + (HZ * sleep_time) / 1000);
+			mod_timer(&(tz->timer), timeout_jiffies);
 		else {
 			tz->timer.data = (unsigned long)tz;
 			tz->timer.function = acpi_thermal_run;
-			tz->timer.expires = jiffies + (HZ * sleep_time) / 1000;
+			tz->timer.expires = timeout_jiffies;
 			add_timer(&(tz->timer));
 		}
 	}