[ACPI] update passive cooling algorithm

	from Dominik Brodowski

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.)

diff --git a/drivers/acpi/processor.c b/drivers/acpi/processor.c
index b472015bb9457b87041fc0f4189f75e8d4b9d411..ad2374d3389655e0bc7160dfe9e5147427168ce8 100644 (file)
--- a/drivers/acpi/processor.c
+++ b/drivers/acpi/processor.c
@@ -1091,6 +1091,113 @@ end:
 }
 
 
+#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 @@ acpi_processor_set_thermal_limit (
        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 @@ acpi_processor_set_thermal_limit (
        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 @@ acpi_processor_set_thermal_limit (
         * 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 @@ acpi_processor_set_thermal_limit (
                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;
+       if (pr->flags.throttling) {
+               pr->limit.thermal.px = 0;
+               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"));
+               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));
+               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 @@ acpi_processor_init (void)
                return_VALUE(-ENODEV);
        }
 
+       acpi_thermal_cpufreq_init();
+
        return_VALUE(0);
 }
 
@@ -1822,6 +1930,8 @@ acpi_processor_exit (void)
 {
        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);