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SubjectRe: [PATCH 1/2] PM / devfreq: Add debugfs support with devfreq_summary file
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On 1/8/20 11:14 PM, Dmitry Osipenko wrote:
> 08.01.2020 10:56, Chanwoo Choi пишет:
>> On 1/8/20 6:15 AM, Bjorn Andersson wrote:
>>> On Tue 07 Jan 01:05 PST 2020, Chanwoo Choi wrote:
>>>
>>>> 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.
>>>> - 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]
>>>> - In order to show the multiple governors on devfreq_summay result,
>>>> change the governor of devfreq0 from simple_ondemand to userspace.
>>>>
>>>> $ 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 userspace 0 206000000 165000000 825000000
>>>> soc:bus_wcore devfreq1 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 0 83250000 333000000
>>>> soc:bus_g2d_acp devfreq10 devfreq1 passive 0 0 66500000 266000000
>>>> soc:bus_jpeg devfreq11 devfreq1 passive 0 0 75000000 300000000
>>>> soc:bus_jpeg_apb devfreq12 devfreq1 passive 0 0 83250000 166500000
>>>> soc:bus_disp1_fimd devfreq13 devfreq1 passive 0 0 120000000 200000000
>>>> soc:bus_disp1 devfreq14 devfreq1 passive 0 0 120000000 300000000
>>>> soc:bus_gscl_scaler devfreq15 devfreq1 passive 0 0 150000000 300000000
>>>> soc:bus_mscl devfreq16 devfreq1 passive 0 0 84000000 666000000
>>>
>>> This looks quite useful.
>>>
>>>>
>>>> Reported-by: kbuild test robot <lkp@intel.com>
>>>
>>> May I ask how the build test robot came up with this idea?
>>
>> I'm missing the detailed what are the reported by kbuild test robot.
>> It reported the possible build error. I'll add the following description
>> on next version:
>> [lkp: Reported the build error]
>>
>>>
>>>> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
>>>> ---
>>>> drivers/devfreq/devfreq.c | 80 +++++++++++++++++++++++++++++++++++++++
>>>> 1 file changed, 80 insertions(+)
>>>>
>>>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>>> [..]
>>>> +/**
>>>> + * devfreq_summary_show() - Show the summary of the registered devfreq devices
>>>> + * via 'devfreq_summary' debugfs file.
>>>
>>> Please make this proper kerneldoc, i.e:
>>>
>>> * func() - short description
>>> * @s:
>>> * @data:
>>> *
>>> * Long description
>>> *
>>> * Return: foo on bar
>>
>> OK.
>>
>>>
>>> [..]
>>>> @@ -1733,6 +1803,16 @@ static int __init devfreq_init(void)
>>>> }
>>>> devfreq_class->dev_groups = devfreq_groups;
>>>>
>>>> + devfreq_debugfs = debugfs_create_dir("devfreq", NULL);
>>>> + if (PTR_ERR(devfreq_debugfs) != -ENODEV && IS_ERR(devfreq_debugfs)) {
>>>
>>> Don't PTR_ERR() before IS_ERR().
>>
>> Before checking IS_ERR(), have to check the PTR_ERR(devfreq_debugfs)
>> is -ENODEV or not because debugfs_create_dir return the '-ENODEV'
>> if DEBUG_FS is disabled. If return the -ENODEV, it is not error.
>
> You could write it this way:
>
> devfreq_debugfs = debugfs_create_dir("devfreq", NULL);
> err = PTR_ERR_OR_ZERO(devfreq_debugfs);
> if (err && err != -ENODEV) {

It is same result between your suggestion and following statement'
without any separate local variable.

if (IS_ERR(devfreq_debugfs) && PTR_ERR(devfreq_debugfs) != -ENODEV)


> ...
>
>


--
Best Regards,
Chanwoo Choi
Samsung Electronics

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