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cpufreq: arm_big_little: set 'physical_cluster' for each CPU 

We have a per-CPU variable for managing which cluster a CPU belongs to.
Currently, physical_cluster is set for policy->cpu only which leads to
the following on some SoC's:

 - There are two clusters:
   - Cluster 0 has four ARM Cortex A7 CPUs (slower ones): 0,1,2,3
   - Cluster 1 has four ARM Cortex A15 CPUs (faster ones): 4,5,6,7
 - CPUs are booted in order 0,1..7 and so initially policy->cpu for A7 cluster
   would be 0 and for A15 cluster would be 4.
 - Now CPU4 (i.e. A15_0) is hotplugged out and so policy->cpu for A15 cluster
   becomes 5 (i.e. A15_1).
 - But physical cluster is only set for CPU0 and CPU4 in ARM big LITTLE driver
   and isn't updated.
 - Now freq change request comes for A15 cluster and we would try to update freq
   of physical_cluster of CPU5, i.e. A15_1. And it is currently set to zero
   (default value of uninitialized global variables).
 - And so we actually try to change freq of A7 cluster instead of A15.
 - This also results in kernel crash as sometimes we might request freq above
   A7's limit and CPU may behave badly..

Fix this by initializing physical_cluster for all CPUs of a policy.

Based on previous work by Xin Wang.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
viresh kumar 2014-03-14 12:10:55 +05:30 committed by Rafael J. Wysocki
parent 3b84d58d42
commit 8f3ba3d325
1 changed files with 4 additions and 1 deletions
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5
drivers/cpufreq/arm_big_little.c
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@ -446,9 +446,12 @@ static int bL_cpufreq_init(struct cpufreq_policy *policy)
}
if (cur_cluster < MAX_CLUSTERS) {
int cpu;
cpumask_copy(policy->cpus, topology_core_cpumask(policy->cpu));
per_cpu(physical_cluster, policy->cpu) = cur_cluster;
for_each_cpu(cpu, policy->cpus)
per_cpu(physical_cluster, cpu) = cur_cluster;
} else {
/* Assumption: during init, we are always running on A15 */
per_cpu(physical_cluster, policy->cpu) = A15_CLUSTER;