arch_topology: Introduce thermal pressure update function

The thermal pressure is a mechanism which is used for providing
information about reduced CPU performance to the scheduler. Usually code
has to convert the value from frequency units into capacity units,
which are understandable by the scheduler. Create a common conversion code
which can be just used via a handy API.

Internally, the topology_update_thermal_pressure() operates on frequency
in MHz and max CPU frequency is taken from 'freq_factor' (per-cpu).

Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Reviewed-by: Thara Gopinath <thara.gopinath@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

1 files changed, 42 insertions, 1 deletions

diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index ff16a36a908b..a3ae0b4eea09 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -22,6 +22,7 @@
 static DEFINE_PER_CPU(struct scale_freq_data __rcu *, sft_data);
 static struct cpumask scale_freq_counters_mask;
 static bool scale_freq_invariant;
+static DEFINE_PER_CPU(u32, freq_factor) = 1;
 
 static bool supports_scale_freq_counters(const struct cpumask *cpus)
 {
@@ -165,6 +166,47 @@ void topology_set_thermal_pressure(const struct cpumask *cpus,
 }
 EXPORT_SYMBOL_GPL(topology_set_thermal_pressure);
 
+/**
+ * topology_update_thermal_pressure() - Update thermal pressure for CPUs
+ * @cpus        : The related CPUs for which capacity has been reduced
+ * @capped_freq : The maximum allowed frequency that CPUs can run at
+ *
+ * Update the value of thermal pressure for all @cpus in the mask. The
+ * cpumask should include all (online+offline) affected CPUs, to avoid
+ * operating on stale data when hot-plug is used for some CPUs. The
+ * @capped_freq reflects the currently allowed max CPUs frequency due to
+ * thermal capping. It might be also a boost frequency value, which is bigger
+ * than the internal 'freq_factor' max frequency. In such case the pressure
+ * value should simply be removed, since this is an indication that there is
+ * no thermal throttling. The @capped_freq must be provided in kHz.
+ */
+void topology_update_thermal_pressure(const struct cpumask *cpus,
+				      unsigned long capped_freq)
+{
+	unsigned long max_capacity, capacity;
+	u32 max_freq;
+	int cpu;
+
+	cpu = cpumask_first(cpus);
+	max_capacity = arch_scale_cpu_capacity(cpu);
+	max_freq = per_cpu(freq_factor, cpu);
+
+	/* Convert to MHz scale which is used in 'freq_factor' */
+	capped_freq /= 1000;
+
+	/*
+	 * Handle properly the boost frequencies, which should simply clean
+	 * the thermal pressure value.
+	 */
+	if (max_freq <= capped_freq)
+		capacity = max_capacity;
+	else
+		capacity = mult_frac(max_capacity, capped_freq, max_freq);
+
+	arch_set_thermal_pressure(cpus, max_capacity - capacity);
+}
+EXPORT_SYMBOL_GPL(topology_update_thermal_pressure);
+
 static ssize_t cpu_capacity_show(struct device *dev,
 				 struct device_attribute *attr,
 				 char *buf)
@@ -217,7 +259,6 @@ static void update_topology_flags_workfn(struct work_struct *work)
 	update_topology = 0;
 }
 
-static DEFINE_PER_CPU(u32, freq_factor) = 1;
 static u32 *raw_capacity;
 
 static int free_raw_capacity(void)