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

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

On 1/14/20 11:51 AM, Dmitry Osipenko wrote:
> 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 IS_ENABLED(CONFIG_DEVFREQ_GOV_PASSIVE) 

>>>> +		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.

This path has the problem. I'm missing that.

'struct devfreq_passive_data' is only defined
when CONFIG_DEVFREQ_GOV_PASSIVE is enabled.

In case of when CONFIG_DEVFREQ_GOV_PASSIVE is disabled,
p_devfreq should be initialized with NULL as following:
I'll modify this patch as following:

struct devfreq *p_devfreq = NULL;

#if IS_ENABLED(CONFIG_DEVFREQ_GOV_PASSIVE) 
	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;
#endif


> 
>>>> +		} 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.

ok.

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


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics