cpufreq: Simplify __cpufreq_remove_dev()

__cpufreq_remove_dev() is called on multiple occasions: cpufreq_driver
unregister and cpu removals.

Current implementation of this routine is overly complex without much need. If
the cpu to be removed is the policy->cpu, we remove the policy first and add all
other cpus again from policy->cpus and then finally call __cpufreq_remove_dev()
again to remove the cpu to be deleted. Haahhhh..

There exist a simple solution to removal of a cpu:
- Simply use the old policy structure
- update its fields like: policy->cpu, etc.
- notify any users of cpufreq, which depend on changing policy->cpu

Hence this patch, which tries to implement the above theory. It is tested well
by myself on ARM big.LITTLE TC2 SoC, which has 5 cores (2 A15 and 3 A7). Both
A15's share same struct policy and all A7's share same policy structure.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 25 insertions, 2 deletions

diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c
index 9d7732b81044..beef6b54382b 100644
--- a/drivers/cpufreq/cpufreq_stats.c
+++ b/drivers/cpufreq/cpufreq_stats.c
@@ -170,11 +170,13 @@ static int freq_table_get_index(struct cpufreq_stats *stat, unsigned int freq)
 static void cpufreq_stats_free_table(unsigned int cpu)
 {
         struct cpufreq_stats *stat = per_cpu(cpufreq_stats_table, cpu);
+
         if (stat) {
+                pr_debug("%s: Free stat table\n", __func__);
                 kfree(stat->time_in_state);
                 kfree(stat);
+                per_cpu(cpufreq_stats_table, cpu) = NULL;
         }
-        per_cpu(cpufreq_stats_table, cpu) = NULL;
 }
 
 /* must be called early in the CPU removal sequence (before
@@ -183,8 +185,10 @@ static void cpufreq_stats_free_table(unsigned int cpu)
 static void cpufreq_stats_free_sysfs(unsigned int cpu)
 {
         struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
-        if (policy && policy->cpu == cpu)
+        if (policy && (cpumask_weight(policy->cpus) == 1)) {
+                pr_debug("%s: Free sysfs stat\n", __func__);
                 sysfs_remove_group(&policy->kobj, &stats_attr_group);
+        }
         if (policy)
                 cpufreq_cpu_put(policy);
 }
@@ -262,6 +266,19 @@ error_get_fail:
         return ret;
 }
 
+static void cpufreq_stats_update_policy_cpu(struct cpufreq_policy *policy)
+{
+        struct cpufreq_stats *stat = per_cpu(cpufreq_stats_table,
+                        policy->last_cpu);
+
+        pr_debug("Updating stats_table for new_cpu %u from last_cpu %u\n",
+                        policy->cpu, policy->last_cpu);
+        per_cpu(cpufreq_stats_table, policy->cpu) = per_cpu(cpufreq_stats_table,
+                        policy->last_cpu);
+        per_cpu(cpufreq_stats_table, policy->last_cpu) = NULL;
+        stat->cpu = policy->cpu;
+}
+
 static int cpufreq_stat_notifier_policy(struct notifier_block *nb,
                 unsigned long val, void *data)
 {
@@ -269,6 +286,12 @@ static int cpufreq_stat_notifier_policy(struct notifier_block *nb,
         struct cpufreq_policy *policy = data;
         struct cpufreq_frequency_table *table;
         unsigned int cpu = policy->cpu;
+
+        if (val == CPUFREQ_UPDATE_POLICY_CPU) {
+                cpufreq_stats_update_policy_cpu(policy);
+                return 0;
+        }
+
         if (val != CPUFREQ_NOTIFY)
                 return 0;
         table = cpufreq_frequency_get_table(cpu);