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Date: Wed, 10 Jul 2013 17:30:46 +0900
From: Chanwoo Choi <cw00.choi@...sung.com>
To: Viresh Kumar <viresh.kumar@...aro.org>
Cc: rjw@...k.pl, linux-kernel@...r.kernel.org,
linux-pm@...r.kernel.org, cpufreq@...r.kernel.org,
kyungmin.park@...sung.com, myungjoo.ham@...sung.com
Subject: Re: [PATCH 1/6] cpufreq: Add debugfs directory for cpufreq
Hi Viresh,
On 07/09/2013 06:23 PM, Viresh Kumar wrote:
> On 5 July 2013 14:16, Chanwoo Choi <cw00.choi@...sung.com> wrote:
>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
>
>> +/* The cpufreq_debugfs is used to create debugfs root directory for CPUFreq. */
>> +#define MAX_DEBUGFS_NAME_LEN CPUFREQ_NAME_LEN
>
> Why declare MAX_DEBUGFS_NAME_LEN if it is going to be equal to
> CPUFREQ_NAME_LEN. Simply use CPUFREQ_NAME_LEN everywhere.
OK, I'll use CPUFREQ_NAME_LEN instead of defining CPUFREQ_NAME_LEN.
>
>> +static struct dentry *cpufreq_debugfs;
>
> Probably make this dependent on CONFIG_CPU_FREQ_STAT?
I thought that '/sys/kernel/debug/cpufreq' is always created in the same as sysfs file
when added cpufreq driver. Only the debugfs file(/sys/kernel/debug/cpufreq/load_table)
has the dependency on CONFIG_CPU_FREQ_STAT.
If *cpufreq_debugfs has the dependency on CONFIG_CPU_FREQ_STAT,
I should add checking statement with '#ifdef CONFIG_CPU_FREQ_STAT' keyword in cpufreq.c.
What is your opinion to add the dependency of CONFIG_CPU_FREQ_STAT
in cpufreq.c?
>
>> /*
>> * 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");
>
> pr_err?
I'll fix it.
>
>> + }
>> }
>> 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;
>
> NR_CPUS? You only need to take care of cpus that belong to this
> policy, isn't it? policy->related_cpus should be good enough for you.
You're right. I'll fix it.
I didn't think using policy->related_cpus instead of 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");
>> + }
>
> pr_err?
I'll fix it.
>
> And move this code just before the call to cpufreq_add_dev_symlink().
OK, I'll move it.
>
>> /* 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");
>> + }
>
> This is purely replication of same code. Create a routine to
> hold these lines and call it from wherever it is required.
OK, I'll create a routine which create symbolic link of debugfs directory.
>
>> 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]);
>> } 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]);
>
> So you removed load_table here? What about other cpus that were
> there in policy->cpus?
You're right. This code is wrong. I'll consider other way to resolve this case.
>
>> + debugfs_remove(cpufreq_debugfs);
>
> Who will create this again? Also, there might be multiple policy struct's
> in a system and here we have reached to removal of all cpus of
> a policy. Other policies are still alive.
OK, I'll control 'debugfs' directory in cpufreq_register/unregister_driver().
>
>> 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");
>
> So, you just added this directory once.. So you must not
> remove it.
I'll add 'debugfs' directory in cpufreq_register_driver()
and remove it in cpufreq_unregister_driver().
>
>> return 0;
>> }
>> core_initcall(cpufreq_core_init);
>
Thanks for your comment.
Best Regards,
Chanwoo Choi
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