Re: [PATCH v3] PM / devfreq: Add debugfs support with devfreq_summary file

[Dmitry Osipenko <digetx@gmail.com>]

14.01.2020 05:23, Chanwoo Choi пишет:
> On 1/14/20 10:45 AM, Dmitry Osipenko wrote:
>> 14.01.2020 04:45, Chanwoo Choi пишет:
>>> Add debugfs interface to provide debugging information of devfreq device.
>>> It contains 'devfreq_summary' entry to show the summary of registered
>>> devfreq devices as following and the additional debugfs file will be added.
>>> - /sys/kernel/debug/devfreq/devfreq_summary
>>>
>>> [Detailed description of each field of 'devfreq_summary' debugfs file]
>>> - dev_name	: Device name of h/w.
>>> - dev		: Device name made by devfreq core.
>>> - parent_dev	: If devfreq device uses the passive governor,
>>> 		  show parent devfreq device name. Otherwise, show 'null'.
>>> - governor	: Devfreq governor.
>>> - polling_ms	: If devfreq device uses the simple_ondemand governor,
>>> 		  polling_ms is necessary for the period. (unit: millisecond)
>>> - cur_freq_Hz	: Current Frequency (unit: Hz)
>>> - old_freq_Hz	: Frequency before changing. (unit: Hz)
>>> - new_freq_Hz	: Frequency after changed. (unit: Hz)
>>>
>>> [For example on Exynos5422-based Odroid-XU3 board]
>>> $ cat /sys/kernel/debug/devfreq/devfreq_summary
>>> dev_name                       dev        parent_dev governor        polling_ms  cur_freq_Hz  min_freq_Hz  max_freq_Hz
>>> ------------------------------ ---------- ---------- --------------- ---------- ------------ ------------ ------------
>>> 10c20000.memory-controller     devfreq0   null       simple_ondemand          0    165000000    165000000    825000000
>>> soc:bus_wcore                  devfreq1   null       simple_ondemand         50    532000000     88700000    532000000
>>> soc:bus_noc                    devfreq2   devfreq1   passive                  0    111000000     66600000    111000000
>>> soc:bus_fsys_apb               devfreq3   devfreq1   passive                  0    222000000    111000000    222000000
>>> soc:bus_fsys                   devfreq4   devfreq1   passive                  0    200000000     75000000    200000000
>>> soc:bus_fsys2                  devfreq5   devfreq1   passive                  0    200000000     75000000    200000000
>>> soc:bus_mfc                    devfreq6   devfreq1   passive                  0    333000000     83250000    333000000
>>> soc:bus_gen                    devfreq7   devfreq1   passive                  0    266000000     88700000    266000000
>>> soc:bus_peri                   devfreq8   devfreq1   passive                  0     66600000     66600000     66600000
>>> soc:bus_g2d                    devfreq9   devfreq1   passive                  0    333000000     83250000    333000000
>>> soc:bus_g2d_acp                devfreq10  devfreq1   passive                  0    266000000     66500000    266000000
>>> soc:bus_jpeg                   devfreq11  devfreq1   passive                  0    300000000     75000000    300000000
>>> soc:bus_jpeg_apb               devfreq12  devfreq1   passive                  0    166500000     83250000    166500000
>>> soc:bus_disp1_fimd             devfreq13  devfreq1   passive                  0    200000000    120000000    200000000
>>> soc:bus_disp1                  devfreq14  devfreq1   passive                  0    300000000    120000000    300000000
>>> soc:bus_gscl_scaler            devfreq15  devfreq1   passive                  0    300000000    150000000    300000000
>>> soc:bus_mscl                   devfreq16  devfreq1   passive                  0    666000000     84000000    666000000
>>>
>>> [lkp: Reported the build error]
>>> Reported-by: kbuild test robot <lkp@intel.com>
>>> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
>>> ---
>>> Changes from v2:
>>> - Show 'null' at 'parent_dev' field when governor of devfreq device
>>>   is not passive
>>> Changes from v1:
>>> - Drop the patch about 'devfreq_transitions' debugfs file
>>> - Modify from 'hz' to 'Hz'
>>> - Edit the indentation of 'devfreq_summary' when show summary
>>> - Exchange sequence between PTR_ERR and IS_ERR when debugfs_create_dir
>>>
>>>  drivers/devfreq/devfreq.c | 84 +++++++++++++++++++++++++++++++++++++++
>>>  1 file changed, 84 insertions(+)
>>>
>>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>>> index 89260b17598f..c5ef2d194b1b 100644
>>> --- a/drivers/devfreq/devfreq.c
>>> +++ b/drivers/devfreq/devfreq.c
>>> @@ -10,6 +10,7 @@
>>>  #include <linux/kernel.h>
>>>  #include <linux/kmod.h>
>>>  #include <linux/sched.h>
>>> +#include <linux/debugfs.h>
>>>  #include <linux/errno.h>
>>>  #include <linux/err.h>
>>>  #include <linux/init.h>
>>> @@ -33,6 +34,7 @@
>>>  #define HZ_PER_KHZ	1000
>>>  
>>>  static struct class *devfreq_class;
>>> +static struct dentry *devfreq_debugfs;
>>>  
>>>  /*
>>>   * devfreq core provides delayed work based load monitoring helper
>>> @@ -1643,6 +1645,79 @@ static struct attribute *devfreq_attrs[] = {
>>>  };
>>>  ATTRIBUTE_GROUPS(devfreq);
>>>  
>>> +/**
>>> + * devfreq_summary_show() - Show the summary of the devfreq devices
>>> + * @s:		seq_file instance to show the summary of devfreq devices
>>> + * @data:	not used
>>> + *
>>> + * Show the summary of the devfreq devices via 'devfreq_summary' debugfs file.
>>> + * It helps that user can know the detailed information of the devfreq devices.
>>> + *
>>> + * Return 0 always because it shows the information without any data change.
>>> + */
>>> +static int devfreq_summary_show(struct seq_file *s, void *data)
>>> +{
>>> +	struct devfreq *devfreq;
>>> +	struct devfreq *p_devfreq = NULL;

Looks like there is no need to pre-initialize the p_devfreq, please see
below.

>>> +	unsigned long cur_freq, min_freq, max_freq;
>>> +	unsigned int polling_ms;
>>> +
>>> +	seq_printf(s, "%-30s %-10s %-10s %-15s %10s %12s %12s %12s\n",
>>> +			"dev_name",
>>> +			"dev",
>>> +			"parent_dev",
>>> +			"governor",
>>> +			"polling_ms",
>>> +			"cur_freq_Hz",
>>> +			"min_freq_Hz",
>>> +			"max_freq_Hz");
>>> +	seq_printf(s, "%30s %10s %10s %15s %10s %12s %12s %12s\n",
>>> +			"------------------------------",
>>> +			"----------",
>>> +			"----------",
>>> +			"---------------",
>>> +			"----------",
>>> +			"------------",
>>> +			"------------",
>>> +			"------------");
>>> +
>>> +	mutex_lock(&devfreq_list_lock);
>>> +
>>> +	list_for_each_entry_reverse(devfreq, &devfreq_list, node) {
>>> +		if (!strncmp(devfreq->governor_name, DEVFREQ_GOV_PASSIVE,
>>> +							DEVFREQ_NAME_LEN)) {
>>> +			struct devfreq_passive_data *data = devfreq->data;
>>> +
>>> +			if (data)
>>> +				p_devfreq = data->parent;

			else
				p_devfreq = NULL;

Otherwise p_devfreq will be reused from a previous devfreq device if
that device has the data->parent.

>>> +		} else {
>>> +			p_devfreq = NULL;
>>> +		}
>>> +
>>> +		mutex_lock(&devfreq->lock);
>>> +		cur_freq = devfreq->previous_freq,
>>> +		get_freq_range(devfreq, &min_freq, &max_freq);
>>> +		polling_ms = devfreq->profile->polling_ms,
>>> +		mutex_unlock(&devfreq->lock);
>>> +
>>> +		seq_printf(s,
>>> +			"%-30s %-10s %-10s %-15s %10d %12ld %12ld %12ld\n",
>>> +			dev_name(devfreq->dev.parent),
>>> +			dev_name(&devfreq->dev),
>>> +			p_devfreq ? dev_name(&p_devfreq->dev) : "null",
>>> +			devfreq->governor_name,
>>> +			polling_ms,
>>> +			cur_freq,
>>> +			min_freq,
>>> +			max_freq);
>>> +	}
>>> +
>>> +	mutex_unlock(&devfreq_list_lock);
>>> +
>>> +	return 0;
>>> +}
>>> +DEFINE_SHOW_ATTRIBUTE(devfreq_summary);
>>> +
>>>  static int __init devfreq_init(void)
>>>  {
>>>  	devfreq_class = class_create(THIS_MODULE, "devfreq");
>>> @@ -1659,6 +1734,15 @@ static int __init devfreq_init(void)
>>>  	}
>>>  	devfreq_class->dev_groups = devfreq_groups;
>>>  
>>> +	
>> If you'll you'll take a look at [2], you may notice notice that it
>> checks whether devfreq_debugfs IS_ERR [3] and then bails out.
>>
>> [2] https://protect2.fireeye.com/url?k=a5047d02-f8ca7cd1-a505f64d-000babff317b-ed64c541cd573190&u=https://elixir.bootlin.com/linux/v5.5-rc6/source/fs/debugfs/inode.c#L432
>> [3] https://protect2.fireeye.com/url?k=0a43fffa-578dfe29-0a4274b5-000babff317b-1c1c1062bfaeb0fc&u=https://elixir.bootlin.com/linux/v5.5-rc6/source/fs/debugfs/inode.c#L316
>>
>> Thus you could simply remove the above error handling, making code to
>> look cleaner.
>>
>>
> 
> OK. I'll modify it as following: Do you agree?

Looks good, thanks.

> 	devfreq_debugfs = debugfs_create_dir("devfreq", NULL);

I'd also add a newline here, to ease reading of the code.

> 	debugfs_create_file("devfreq_summary", 0444,
> 			devfreq_debugfs, NULL,
> 			&devfreq_summary_fops);
> 
>