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SubjectRe: [PATCH v3 4/8] PM / devfreq: Show the all available frequencies
On Wed, Oct 11, 2017 at 8:26 PM, MyungJoo Ham <myungjoo.ham@samsung.com> wrote:
>> The commit a76caf55e5b35 ("thermal: Add devfreq cooling") allows
>> the devfreq device to use the cooling device. When the cooling down
>> are required, the devfreq_cooling.c disables the OPP entry with
>> the dev_pm_opp_disable(). In result, 'available_frequencies'[1]
>> sysfs node never came to show the all available frequencies.
>> [1] /sys/class/devfreq/.../available_frequencies
>>
>> So, this patch uses the 'freq_table' in the 'struct devfreq_dev_profile'
>> in order to show the all available frequencies.
>> - If 'freq_table' is NULL, devfreq core initializes them by using OPP values.
>> - If 'freq_table' is initialized, devfreq core just uses the 'freq_table'.
>>
>> Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
>> ---
>> drivers/devfreq/devfreq.c | 28 ++++++++++++++++------------
>> 1 file changed, 16 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>> index 799a0cf75d39..1c4b377cacfb 100644
>> --- a/drivers/devfreq/devfreq.c
>> +++ b/drivers/devfreq/devfreq.c
>> @@ -1185,22 +1185,26 @@ static ssize_t available_frequencies_show(struct device *d,
>> char *buf)
>> {
>> struct devfreq *df = to_devfreq(d);
>> - struct device *dev = df->dev.parent;
>> - struct dev_pm_opp *opp;
>> ssize_t count = 0;
>> - unsigned long freq = 0;
>> + unsigned long *freq_table;
>> + int i, max_state;
>>
>> - do {
>> - opp = dev_pm_opp_find_freq_ceil(dev, &freq);
>> - if (IS_ERR(opp))
>> - break;
>> + mutex_lock(&df->lock);
>>
>> - dev_pm_opp_put(opp);
>> - count += scnprintf(&buf[count], (PAGE_SIZE - count - 2),
>> - "%lu ", freq);
>> - freq++;
>> - } while (1);
>> + freq_table = df->profile->freq_table;
>> + max_state = df->profile->max_state;
>>
>> + if (freq_table[0] < freq_table[max_state - 1]) {
>> + for (i = 0; i < max_state; i++)
>> + count += scnprintf(&buf[count], (PAGE_SIZE - count - 2),
>> + "%lu ", freq_table[i]);
>> + } else {
>> + for (i = max_state - 1; i >= 0 ; i--)
>> + count += scnprintf(&buf[count], (PAGE_SIZE - count - 2),
>> + "%lu ", freq_table[i]);
>
> Is there a possibilty that PC will hit here?

As I commented on patch description, the 'freq_table' is always filled
with frequency as following description: There is no issue on both
embedded and PC.
--------
- If 'freq_table' is NULL, devfreq core initializes them by using OPP values.
- If 'freq_table' is initialized, devfreq core just uses the 'freq_table'.
--------

> (If so, don't you need to worry about not being sorted at all?)
>
> At least, devfreq_set_freq_table sorts it in ascending order.
> And if you are worried about someone not using devfreq_set_freq_table
> and set freq_table on their own, we'd better simple put some comments
> to mandate it to be sorted in ascending order or not allowing to do it
> anyway.

OK. I'll just consider the ascending order and then I'll add some comments
for that the ascending order is mandatory for 'freq_table'.

(Actually. the ARM Mali kernel driver makes the 'freq_table'
in the descending order. It doesn't matter. As you commented,
I'll add the comment about the ordering way.)

>
> Cheers,
> MyungJoo.
>
>> + }
>> +
>> + mutex_unlock(&df->lock);
>> /* Truncate the trailing space */
>> if (count)
>> count--;

--
Best Regards,
Chanwoo Choi
Samsung Electronics

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