Re: [PATCH 1/6] cpufreq: Add debugfs directory for cpufreq

[Chanwoo Choi <cw00.choi@samsung.com>]

Hi Pankaj,

On 07/08/2013 03:54 AM, Pankaj Jangra wrote:
> Hi Chanwoo,
> 
> On Fri, Jul 5, 2013 at 1:46 AM, Chanwoo Choi <cw00.choi@samsung.com> wrote:
>> This patch create debugfs root directory and child directory according to
>> the number of CPUs for CPUFreq as below debugfs directory path:
>> - /sys/kernel/debug/cpufreq/cpuX
>>
>> If many CPUs share only one cpufreq policy, other CPU(except for CPU0) create
>> a link for debugfs directory of CPU0.
>> - /sys/kernel/debug/cpufreq/cpu0
>> - /sys/kernel/debug/cpufreq/cpu[1-(N-1)] -> /sys/kernel/debug/cpufreq/cpu0
>>
>> And then cpufreq may need to create debugfs specific file below of debugfs
>> directory of cpufreq. (e.g., /sys/kernel/debug/cpufreq/cpu0/load_table)
>>
>> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
>> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
>> Signed-off-by: Myungjoo Ham <myungjoo.ham@samsung.com>
>> ---
>>  drivers/cpufreq/cpufreq.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++
>>  include/linux/cpufreq.h   |  1 +
>>  2 files changed, 58 insertions(+)
>>
>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
>> index 2d53f47..bc01c8e 100644
>> --- a/drivers/cpufreq/cpufreq.c
>> +++ b/drivers/cpufreq/cpufreq.c
>> @@ -23,6 +23,7 @@
>>  #include <linux/notifier.h>
>>  #include <linux/cpufreq.h>
>>  #include <linux/delay.h>
>> +#include <linux/debugfs.h>
>>  #include <linux/interrupt.h>
>>  #include <linux/spinlock.h>
>>  #include <linux/device.h>
>> @@ -47,6 +48,10 @@ static DEFINE_PER_CPU(char[CPUFREQ_NAME_LEN], cpufreq_cpu_governor);
>>  #endif
>>  static DEFINE_RWLOCK(cpufreq_driver_lock);
>>
>> +/* The cpufreq_debugfs is used to create debugfs root directory for CPUFreq. */
>> +#define MAX_DEBUGFS_NAME_LEN   CPUFREQ_NAME_LEN
>> +static struct dentry *cpufreq_debugfs;
>> +
>>  /*
>>   * cpu_policy_rwsem is a per CPU reader-writer semaphore designed to cure
>>   * all cpufreq/hotplug/workqueue/etc related lock issues.
>> @@ -726,6 +731,20 @@ static int cpufreq_add_dev_symlink(unsigned int cpu,
>>                         cpufreq_cpu_put(managed_policy);
>>                         return ret;
>>                 }
>> +
>> +               if (cpufreq_debugfs) {
>> +                       char symlink_name[MAX_DEBUGFS_NAME_LEN];
>> +                       char target_name[MAX_DEBUGFS_NAME_LEN];
>> +
>> +                       sprintf(symlink_name, "cpu%d", j);
>> +                       sprintf(target_name, "./cpu%d", cpu);
>> +                       managed_policy->cpu_debugfs[j] = debugfs_create_symlink(
>> +                                                       symlink_name,
>> +                                                       cpufreq_debugfs,
>> +                                                       target_name);
>> +                       if (!managed_policy->cpu_debugfs[j])
>> +                               pr_debug("creating debugfs symlink failed\n");
>> +               }
>>         }
>>         return ret;
>>  }
>> @@ -746,6 +765,22 @@ static int cpufreq_add_dev_interface(unsigned int cpu,
>>         if (ret)
>>                 return ret;
>>
>> +       /* prepare interface data for debugfs */
>> +       if (cpufreq_debugfs) {
>> +               char name[MAX_DEBUGFS_NAME_LEN];
>> +               int size, i;
>> +
>> +               sprintf(name, "cpu%d", policy->cpu);
>> +               size = sizeof(struct dentry*) * NR_CPUS;
>> +               i = cpu;
>> +
>> +               policy->cpu_debugfs = devm_kzalloc(dev, size, GFP_KERNEL);
>> +               policy->cpu_debugfs[i] = debugfs_create_dir(name,
>> +                                                           cpufreq_debugfs);
>> +               if (!policy->cpu_debugfs[i])
>> +                       pr_debug("creating debugfs directory failed\n");
>> +       }
>> +
>>         /* set up files for this cpu device */
>>         drv_attr = cpufreq_driver->attr;
>>         while ((drv_attr) && (*drv_attr)) {
>> @@ -839,6 +874,20 @@ static int cpufreq_add_policy_cpu(unsigned int cpu, unsigned int sibling,
>>                 return ret;
>>         }
>>
>> +       if (cpufreq_debugfs) {
>> +               char symlink_name[MAX_DEBUGFS_NAME_LEN];
>> +               char target_name[MAX_DEBUGFS_NAME_LEN];
>> +
>> +               sprintf(symlink_name, "cpu%d", cpu);
>> +               sprintf(target_name, "./cpu%d", sibling);
>> +               policy->cpu_debugfs[cpu] = debugfs_create_symlink(
>> +                                               symlink_name,
>> +                                               cpufreq_debugfs,
>> +                                               target_name);
>> +               if (!policy->cpu_debugfs[cpu])
>> +                       pr_debug("creating debugfs symlink failed\n");
>> +       }
>> +
>>         return 0;
>>  }
>>  #endif
>> @@ -1046,6 +1095,7 @@ static int __cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif
>>
>>         if (cpu != data->cpu) {
>>                 sysfs_remove_link(&dev->kobj, "cpufreq");
>> +               debugfs_remove(data->cpu_debugfs[cpu]);
> 
> I think you should add the call to remove the "cpufreq" also ???

No, we have to remove 'cpufreq' debugfs directory when the last online CPU is removed.
If condition("cpu != data->cpu") is true, it means that various CPUs share only one cpufreq policy.
When CPU[1-3] is removed, kernel execute first if statement to remove the link of CPU[1-3] debugfs directory.

>                "debugfs_remove(cpufreq_debugfs);"
>>         } else if (cpus > 1) {
>>                 /* first sibling now owns the new sysfs dir */
>>                 cpu_dev = get_cpu_device(cpumask_first(data->cpus));
>> @@ -1068,6 +1118,9 @@ static int __cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif
>>                         return -EINVAL;
>>                 }
>>
>> +               debugfs_remove_recursive(data->cpu_debugfs[cpu]);
>> +               debugfs_remove(cpufreq_debugfs);
>> +
>>                 WARN_ON(lock_policy_rwsem_write(cpu));
>>                 update_policy_cpu(data, cpu_dev->id);
>>                 unlock_policy_rwsem_write(cpu);
>> @@ -1976,6 +2029,10 @@ static int __init cpufreq_core_init(void)
>>         BUG_ON(!cpufreq_global_kobject);
>>         register_syscore_ops(&cpufreq_syscore_ops);
>>
>> +       cpufreq_debugfs = debugfs_create_dir("cpufreq", NULL);
>> +       if (!cpufreq_debugfs)
>> +               pr_debug("creating debugfs root failed\n");
>> +
>>         return 0;
>>  }
>>  core_initcall(cpufreq_core_init);
>> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
>> index 037d36a..825f379 100644
>> --- a/include/linux/cpufreq.h
>> +++ b/include/linux/cpufreq.h
>> @@ -115,6 +115,7 @@ struct cpufreq_policy {
>>
>>         struct kobject          kobj;
>>         struct completion       kobj_unregister;
>> +       struct dentry           **cpu_debugfs;
>>  };
>>
>>  #define CPUFREQ_ADJUST                 (0)
>> --
>> 1.8.0
>>
>> --
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> 
> Regards,
> Pankaj Jangra
> --
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> 

Thanks,
Chanwoo Choi