[RFC v2 07/12] PM / cpu_domains: Add PM Domain governor for CPUs

On 03/01/2016 11:32 AM, Lina Iyer wrote:

On Fri, Feb 26 2016 at 12:33 -0700, Stephen Boyd wrote:

quoted

On 02/12, Lina Iyer wrote:

quoted

@@ -52,6 +55,76 @@ struct cpu_pm_domain *to_cpu_pd(struct

generic_pm_domain *d)
     return res;
 }

+static bool cpu_pd_down_ok(struct dev_pm_domain *pd)
+{
+    struct generic_pm_domain *genpd = pd_to_genpd(pd);
+    struct cpu_pm_domain *cpu_pd = to_cpu_pd(genpd);
+    int qos = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
+    u64 sleep_ns;
+    ktime_t earliest, next_wakeup;
+    int cpu;
+    int i;
+
+    /* Reset the last set genpd state, default to index 0 */
+    genpd->state_idx = 0;
+
+    /* We dont want to power down, if QoS is 0 */
+    if (!qos)
+        return false;
+
+    /*
+     * Find the sleep time for the cluster.
+     * The time between now and the first wake up of any CPU that
+     * are in this domain hierarchy is the time available for the
+     * domain to be idle.
+     */
+    earliest = ktime_set(KTIME_SEC_MAX, 0);
+    for_each_cpu_and(cpu, cpu_pd->cpus, cpu_online_mask) {

We're not worried about hotplug happening in parallel because
preemption is disabled here?

Nope. Hotplug on the same domain or in its hierarchy will be waiting on
the domain lock to released before becoming online. Any other domain is
not of concern for this domain governor.

If a core was hotplugged out while this is happening, then we may risk
making an premature wake up decision, which would happen either way if
we lock hotplug here.

Ok please make this into a comment in the code.

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