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SubjectRe: [PATCH v3 6/7] thermal/drivers/cpu_cooling: Introduce the cpu idle cooling driver
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On 13/04/2018 13:23, Sudeep Holla wrote:
> Hi Daniel,
>
> On 05/04/18 17:16, Daniel Lezcano wrote:
>
> [...]
>
>> +/**
>> + * cpuidle_cooling_register - Idle cooling device initialization function
>> + *
>> + * This function is in charge of creating a cooling device per cluster
>> + * and register it to thermal framework. For this we rely on the
>> + * topology as there is nothing yet describing better the idle state
>> + * power domains.
>> + *
>> + * We create a cpuidle cooling device per cluster. For this reason we
>> + * must, for each cluster, allocate and initialize the cooling device
>> + * and for each cpu belonging to this cluster, do the initialization
>> + * on a cpu basis.
>> + *
>> + * This approach for creating the cooling device is needed as we don't
>> + * have the guarantee the CPU numbering is sequential.
>> + *
>> + * Unfortunately, there is no API to browse from top to bottom the
>> + * topology, cluster->cpu, only the usual for_each_possible_cpu loop.
>> + * In order to solve that, we use a cpumask to flag the cluster_id we
>> + * already processed. The cpumask will always have enough room for all
>> + * the cluster because it is based on NR_CPUS and it is not possible
>> + * to have more clusters than cpus.
>> + *
>> + */
>> +void __init cpuidle_cooling_register(void)
>> +{
>> + struct cpuidle_cooling_device *idle_cdev = NULL;
>> + struct thermal_cooling_device *cdev;
>> + struct device_node *np;
>> + cpumask_var_t cpumask;
>> + char dev_name[THERMAL_NAME_LENGTH];
>> + int ret = -ENOMEM, cpu;
>> + int cluster_id;
>> +
>> + if (!zalloc_cpumask_var(&cpumask, GFP_KERNEL))
>> + return;
>> +
>> + for_each_possible_cpu(cpu) {
>> +
>> + cluster_id = topology_physical_package_id(cpu);
>> + if (cpumask_test_cpu(cluster_id, cpumask))
>> + continue;
>
> Sorry for chiming in randomly, I haven't read the patches in detail.
> But it was brought to my notice that topology_physical_package_id is
> being used for cluster ID here. It's completely wrong and will
> changesoon with ACPI topology related changes Jeremy is working on.
>
> You will get the physical socket number(which is mostly 0 on single SoC
> system). Makes sure that this won't break with that change.
>
> Please note with cluster id not defined architecturally, relying on that
> is simply problematic.

Ok, noted. At the first glance, it should not be a problem.


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