[PATCH 2.6] update passive cooling algorithm

Dominik Brodowski
2004-01-11T21:12:55Z

[Len, could you test and verify this patch, and push it to Linus, please?]

The current algorithm used by Linux ACPI for passive thermal management has
two shortcomings:

- if increasing the CPU processing power as a thermal situation goes away,
throttling states are decreased later than performance states. This is
not wise -- it should be the opposite ordering of going "up".

- only if the ACPI CPUfreq driver is used, performance states are used.
A generalized approach would offer passive cooling even if the ACPI
P-States cpufreq driver cannot be used (faulty BIOS, FixedHW access, etc.)

The attached patch addresses these issues.

drivers/acpi/processor.c | 182 +++++++++++++++++++++++++++++++++++++----------
1 files changed, 146 insertions(+), 36 deletions(-)

diff -ruN linux-original/drivers/acpi/processor.c linux/drivers/acpi/processor.c
--- linux-original/drivers/acpi/processor.c 2004-01-11 20:51:17.000000000 +0100
+++ linux/drivers/acpi/processor.c 2004-01-11 21:39:43.000000000 +0100
@@ -1091,6 +1091,113 @@
}

+#ifdef CONFIG_CPU_FREQ
+
+/* If a passive cooling situation is detected, primarily CPUfreq is used, as it
+ * offers (in most cases) voltage scaling in addition to frequency scaling, and
+ * thus a cubic (instead of linear) reduction of energy. Also, we allow for
+ * _any_ cpufreq driver and not only the acpi-cpufreq driver.
+ */
+
+static unsigned int cpufreq_thermal_reduction_pctg[NR_CPUS];
+static unsigned int acpi_thermal_cpufreq_is_init = 0;
+
+
+static int cpu_has_cpufreq(unsigned int cpu)
+{
+ struct cpufreq_policy policy;
+ if (!acpi_thermal_cpufreq_is_init)
+ return -ENODEV;
+ if (!cpufreq_get_policy(&policy, cpu))
+ return -ENODEV;
+ return 0;
+}
+
+
+static int acpi_thermal_cpufreq_increase(unsigned int cpu)
+{
+ if (!cpu_has_cpufreq)
+ return -ENODEV;
+
+ if (cpufreq_thermal_reduction_pctg[cpu] < 60) {
+ cpufreq_thermal_reduction_pctg[cpu] += 20;
+ cpufreq_update_policy(cpu);
+ return 0;
+ }
+
+ return -ERANGE;
+}
+
+
+static int acpi_thermal_cpufreq_decrease(unsigned int cpu)
+{
+ if (!cpu_has_cpufreq)
+ return -ENODEV;
+
+ if (cpufreq_thermal_reduction_pctg[cpu] >= 20) {
+ cpufreq_thermal_reduction_pctg[cpu] -= 20;
+ cpufreq_update_policy(cpu);
+ return 0;
+ }
+
+ return -ERANGE;
+}
+
+
+static int acpi_thermal_cpufreq_notifier(
+ struct notifier_block *nb,
+ unsigned long event,
+ void *data)
+{
+ struct cpufreq_policy *policy = data;
+ unsigned long max_freq = 0;
+
+ if (event != CPUFREQ_ADJUST)
+ goto out;
+
+ max_freq = (policy->cpuinfo.max_freq * (100 - cpufreq_thermal_reduction_pctg[policy->cpu])) / 100;
+
+ cpufreq_verify_within_limits(policy, 0, max_freq);
+
+ out:
+ return 0;
+}
+
+
+static struct notifier_block acpi_thermal_cpufreq_notifier_block = {
+ .notifier_call = acpi_thermal_cpufreq_notifier,
+};
+
+
+static void acpi_thermal_cpufreq_init(void) {
+ int i;
+
+ for (i=0; i<NR_CPUS; i++)
+ cpufreq_thermal_reduction_pctg[i] = 0;
+
+ i = cpufreq_register_notifier(&acpi_thermal_cpufreq_notifier_block, CPUFREQ_POLICY_NOTIFIER);
+ if (!i)
+ acpi_thermal_cpufreq_is_init = 1;
+}
+
+static void acpi_thermal_cpufreq_exit(void) {
+ if (acpi_thermal_cpufreq_is_init)
+ cpufreq_unregister_notifier(&acpi_thermal_cpufreq_notifier_block, CPUFREQ_POLICY_NOTIFIER);
+
+ acpi_thermal_cpufreq_is_init = 0;
+}
+
+#else /* ! CONFIG_CPU_FREQ */
+
+static void acpi_thermal_cpufreq_init(void) { return; }
+static void acpi_thermal_cpufreq_exit(void) { return; }
+static int acpi_thermal_cpufreq_increase(unsigned int cpu) { return -ENODEV; }
+static int acpi_thermal_cpufreq_decrease(unsigned int cpu) { return -ENODEV; }
+
+
+#endif
+
+
int
acpi_processor_set_thermal_limit (
acpi_handle handle,
@@ -1099,7 +1206,6 @@
int result = 0;
struct acpi_processor *pr = NULL;
struct acpi_device *device = NULL;
- int px = 0;
int tx = 0;

ACPI_FUNCTION_TRACE("acpi_processor_set_thermal_limit");
@@ -1116,12 +1222,7 @@
if (!pr)
return_VALUE(-ENODEV);

- if (!pr->flags.limit)
- return_VALUE(-ENODEV);
-
/* Thermal limits are always relative to the current Px/Tx state. */
- if (pr->flags.performance)
- pr->limit.thermal.px = pr->performance->state;
if (pr->flags.throttling)
pr->limit.thermal.tx = pr->throttling.state;

@@ -1130,26 +1231,27 @@
* performance state.
*/

- px = pr->limit.thermal.px;
tx = pr->limit.thermal.tx;

switch (type) {

case ACPI_PROCESSOR_LIMIT_NONE:
- px = 0;
+ do {
+ result = acpi_thermal_cpufreq_decrease(pr->id);
+ } while (!result);
tx = 0;
break;

case ACPI_PROCESSOR_LIMIT_INCREMENT:
- if (pr->flags.performance) {
- if (px == (pr->performance->state_count - 1))
- ACPI_DEBUG_PRINT((ACPI_DB_INFO,
+ /* if going up: P-states first, T-states later */
+
+ result = acpi_thermal_cpufreq_increase(pr->id);
+ if (!result)
+ goto end;
+ else if (result == -ERANGE)
+ ACPI_DEBUG_PRINT((ACPI_DB_INFO,
"At maximum performance state\n"));
- else {
- px++;
- goto end;
- }
- }
+
if (pr->flags.throttling) {
if (tx == (pr->throttling.state_count - 1))
ACPI_DEBUG_PRINT((ACPI_DB_INFO,
@@ -1160,37 +1262,41 @@
break;

case ACPI_PROCESSOR_LIMIT_DECREMENT:
- if (pr->flags.performance) {
- if (px == pr->performance_platform_limit)
- ACPI_DEBUG_PRINT((ACPI_DB_INFO,
- "At minimum performance state\n"));
- else {
- px--;
- goto end;
- }
- }
+ /* if going down: T-states first, P-states later */
+
if (pr->flags.throttling) {
if (tx == 0)
ACPI_DEBUG_PRINT((ACPI_DB_INFO,
"At minimum throttling state\n"));
- else
+ else {
tx--;
+ goto end;
+ }
}
+
+ result = acpi_thermal_cpufreq_decrease(pr->id);
+ if (result == -ERANGE)
+ ACPI_DEBUG_PRINT((ACPI_DB_INFO,
+ "At minimum performance state\n"));
+
break;
}

end:
- pr->limit.thermal.px = px;
- pr->limit.thermal.tx = tx;
-
- result = acpi_processor_apply_limit(pr);
- if (result)
- ACPI_DEBUG_PRINT((ACPI_DB_ERROR,
- "Unable to set thermal limit\n"));
+ if (pr->flags.throttling) {
+ pr->limit.thermal.px = 0;
+ pr->limit.thermal.tx = tx;

- ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Thermal limit now (P%d:T%d)\n",
- pr->limit.thermal.px,
- pr->limit.thermal.tx));
+ result = acpi_processor_apply_limit(pr);
+ if (result)
+ ACPI_DEBUG_PRINT((ACPI_DB_ERROR,
+ "Unable to set thermal limit\n"));
+
+ ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Thermal limit now (P%d:T%d)\n",
+ pr->limit.thermal.px,
+ pr->limit.thermal.tx));
+ } else
+ result = 0;

return_VALUE(result);
}
@@ -1813,6 +1919,8 @@
return_VALUE(-ENODEV);
}

+ acpi_thermal_cpufreq_init();
+
return_VALUE(0);
}

@@ -1822,6 +1930,8 @@
{
ACPI_FUNCTION_TRACE("acpi_processor_exit");

+ acpi_thermal_cpufreq_exit();
+
acpi_bus_unregister_driver(&acpi_processor_driver);

remove_proc_entry(ACPI_PROCESSOR_CLASS, acpi_root_dir);