Re: Re: [PATCH v2] PM / devfreq: Use freq_table for available_frequencies

Re: Re: [PATCH v2] PM / devfreq: Use freq_table for available_frequencies

[MyungJoo Ham]

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> On 04/29/2014 01:00 PM, Saravana Kannan wrote:
> > On 04/27/2014 06:41 PM, MyungJoo Ham wrote:
> >> You are hereby changing the semmantics of the original
> >> available_frequencies node.
> >>
> >> When a frequency/voltage pair has been disabled (opp_disable), probably
> >> by opp_disable(), the frequency is no more "available".
> >> However, when the driver author supplied freq_table as well as OPP
> >> in order to see the statistics, the node will behave differently.
> >>
> >> Please do not affect the current users as long as it does not give
> >> additional benefit or fix a bug.
> > 
> > I was actually trying to stick with the semantics as it was documented.
> > The documentation for this file says it'll show frequencies that are not
> > allowed by the current min/max settings either. To me, an OPP disable
> > seems similar to some frequencies "disabled" by min/max settings.
> > 
> > Giving preference to OPP is not a hard change to do, but it seems to go
> > againsts the documented semantics.
> > 
> > Thoughts?
> 
> I'll send out another patch like you wanted -- with OPP being given
> preference over freq_table when listing frequencies.
> 
> But I would still like to hear your thoughts. As of today, there's no
> clean way to get the complete list of available frequencies that would
> give a consistent output irrespective of the temporary limits/conditions
> imposed by thermal, current limiting, etc. The round about way is to cat
> trans_stat and parse the frequencies from that.
> 
> That's why I was trying to give preference to freq_table.
> 
> Thanks,
> Saravana

The node, available_frequencies, was suggested before freq_table concept.
At that time, available_frequencies was supposed to show the list of
available OPP lists for those who use OPP for devfreq device, excluding
those disabled by OPP. (OPP lists are external to devfreq and devfreq's
min/max are internal to devfreq)

Locally, this node has been used to debug the behavior of a devfreq device.
With min/max nodes, we know the range while we cannot (easily at shell)
see which OPP points are available at the moment, where we have been able
to use available_frequencies.

We do not want to lose such capavility as long as we do not have OPP sysfs
automatically assigned to any OPP lists. If I remember correctly, we don't
have it, yet.


A. I want to minimize semantics changes in sysfs. Adding another without
interfering with previous usage is ok.
B. (more importantly) I don't want to lose the debugging capabilities.


Cheers,
MyungJoo.

> 
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> hosted by The Linux Foundation
> 
> 
> 
>        
>   
>          
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Re: [PATCH v2] PM / devfreq: Use freq_table for available_frequencies

[Saravana Kannan]

On 05/08/2014 03:02 AM, MyungJoo Ham wrote:
>> On 04/29/2014 01:00 PM, Saravana Kannan wrote:
>>> On 04/27/2014 06:41 PM, MyungJoo Ham wrote:
>>>> You are hereby changing the semmantics of the original
>>>> available_frequencies node.
>>>>
>>>> When a frequency/voltage pair has been disabled (opp_disable), probably
>>>> by opp_disable(), the frequency is no more "available".
>>>> However, when the driver author supplied freq_table as well as OPP
>>>> in order to see the statistics, the node will behave differently.
>>>>
>>>> Please do not affect the current users as long as it does not give
>>>> additional benefit or fix a bug.
>>>
>>> I was actually trying to stick with the semantics as it was documented.
>>> The documentation for this file says it'll show frequencies that are not
>>> allowed by the current min/max settings either. To me, an OPP disable
>>> seems similar to some frequencies "disabled" by min/max settings.
>>>
>>> Giving preference to OPP is not a hard change to do, but it seems to go
>>> againsts the documented semantics.
>>>
>>> Thoughts?
>>
>> I'll send out another patch like you wanted -- with OPP being given
>> preference over freq_table when listing frequencies.
>>
>> But I would still like to hear your thoughts. As of today, there's no
>> clean way to get the complete list of available frequencies that would
>> give a consistent output irrespective of the temporary limits/conditions
>> imposed by thermal, current limiting, etc. The round about way is to cat
>> trans_stat and parse the frequencies from that.
>>
>> That's why I was trying to give preference to freq_table.
>>
>> Thanks,
>> Saravana
> 
> The node, available_frequencies, was suggested before freq_table concept.
> At that time, available_frequencies was supposed to show the list of
> available OPP lists for those who use OPP for devfreq device, excluding
> those disabled by OPP. (OPP lists are external to devfreq and devfreq's
> min/max are internal to devfreq)
> 
> Locally, this node has been used to debug the behavior of a devfreq device.
> With min/max nodes, we know the range while we cannot (easily at shell)
> see which OPP points are available at the moment, where we have been able
> to use available_frequencies.
> 
> We do not want to lose such capavility as long as we do not have OPP sysfs
> automatically assigned to any OPP lists. If I remember correctly, we don't
> have it, yet.
> 
> 
> A. I want to minimize semantics changes in sysfs. Adding another without
> interfering with previous usage is ok.
> B. (more importantly) I don't want to lose the debugging capabilities.
> 

Thanks for the response MyungJoo. Makes sense. I was also discussing
this internally and was considering a "possible_frequencies" similar to
available vs possible CPUs.

I'll make such a patch for that and send it out. In that case, I'll
probably leave "available_frequencies" alone.

-Saravana

-- 
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hosted by The Linux Foundation

[PATCH v3] PM / devfreq: Add possible_frequencies device attribute

[Saravana Kannan]

Some devices use freq_table instead of OPP. For those devices, the
available_frequencies sysfs file shows up empty. So, add a
possible_frequencies attribute/syfs file that list all the possible
frequencies.

For devices that use OPP, the output of this file will match
available_frequencies. It may change in the future to show all OPP
frequencies -- even the disabled ones.

Signed-off-by: Saravana Kannan <skannan@codeaurora.org>
---
 drivers/devfreq/devfreq.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 9f90369..65eed38 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -994,6 +994,31 @@ static ssize_t available_frequencies_show(struct device *d,
 }
 static DEVICE_ATTR_RO(available_frequencies);
 
+static ssize_t possible_frequencies_show(struct device *d,
+					  struct device_attribute *attr,
+					  char *buf)
+{
+	struct devfreq *df = to_devfreq(d);
+	unsigned int i = 0;
+	ssize_t count = 0;
+
+	if (!df->profile->freq_table)
+		return available_frequencies_show(d, attr, buf);
+
+	for (i = 0; i < df->profile->max_state; i++)
+		count += scnprintf(&buf[count], (PAGE_SIZE - count - 2),
+				   "%u ", df->profile->freq_table[i]);
+
+	/* Truncate the trailing space */
+	if (count)
+		count--;
+
+	count += sprintf(&buf[count], "\n");
+
+	return count;
+}
+static DEVICE_ATTR_RO(possible_frequencies);
+
 static ssize_t trans_stat_show(struct device *dev,
 			       struct device_attribute *attr, char *buf)
 {
@@ -1041,6 +1066,7 @@ static struct attribute *devfreq_attrs[] = {
 	&dev_attr_available_governors.attr,
 	&dev_attr_cur_freq.attr,
 	&dev_attr_available_frequencies.attr,
+	&dev_attr_possible_frequencies.attr,
 	&dev_attr_target_freq.attr,
 	&dev_attr_polling_interval.attr,
 	&dev_attr_min_freq.attr,
-- 
1.8.2.1

The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
hosted by The Linux Foundation

Re: [PATCH v3] PM / devfreq: Add possible_frequencies device attribute

[Saravana Kannan]

On 07/16/2014 05:50 PM, MyungJoo Ham wrote:
> On Wed, Jul 16, 2014 at 12:01 PM, Saravana Kannan <skannan@codeaurora.org> wrote:
>> Some devices use freq_table instead of OPP. For those devices, the
>> available_frequencies sysfs file shows up empty. So, add a
>> possible_frequencies attribute/syfs file that list all the possible
>> frequencies.
>>
>> For devices that use OPP, the output of this file will match
>> available_frequencies. It may change in the future to show all OPP
>> frequencies -- even the disabled ones.
>>
>> Signed-off-by: Saravana Kannan <skannan@codeaurora.org>
> 
> Hi,
> 
> 
> Please add a documentation entry for this new ABI having a little justification and usage included.

Will do.

> 
> Plus, I am considering to move trans_stat along with this entry to somewhere such as .../stat/*
> (you don't need to take care of this.)

Ok.

> 
> Besides, as OPP seems becoming the standard as imagined when devfreq development started,
> soon, devfreq may require OPP unless the devfreq device has continuous frequencies.

I agree. Only one caveat with OPP is that if a device isn't using OPP to
do any voltage scaling, then it forces a voltage column with 0s. Also,
even if we make OPP mandatory, we'll still want trans_stats that
currently seem to depend on freq_table being populated. I was actually
planning on sending out more patches later that'll do a lot of stuff
automatically for devices with OPP. Like creating freq_table, etc.

-Saravana

-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
hosted by The Linux Foundation

Re: [PATCH v3] PM / devfreq: Add possible_frequencies device attribute

[MyungJoo Ham]

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On Wed, Jul 16, 2014 at 12:01 PM, Saravana Kannan <skannan@codeaurora.org> wrote:
> Some devices use freq_table instead of OPP. For those devices, the
> available_frequencies sysfs file shows up empty. So, add a
> possible_frequencies attribute/syfs file that list all the possible
> frequencies.
>
> For devices that use OPP, the output of this file will match
> available_frequencies. It may change in the future to show all OPP
> frequencies -- even the disabled ones.
>
> Signed-off-by: Saravana Kannan <skannan@codeaurora.org>

Hi,


Please add a documentation entry for this new ABI having a little justification and usage included.

Plus, I am considering to move trans_stat along with this entry to somewhere such as .../stat/*
(you don't need to take care of this.)

Besides, as OPP seems becoming the standard as imagined when devfreq development started,
soon, devfreq may require OPP unless the devfreq device has continuous frequencies.

Cheers,
MyungJoo

> ---
>  drivers/devfreq/devfreq.c | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
>
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 9f90369..65eed38 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -994,6 +994,31 @@ static ssize_t available_frequencies_show(struct device *d,
>  }
>  static DEVICE_ATTR_RO(available_frequencies);
>
> +static ssize_t possible_frequencies_show(struct device *d,
> +                                         struct device_attribute *attr,
> +                                         char *buf)
> +{
> +       struct devfreq *df = to_devfreq(d);
> +       unsigned int i = 0;
> +       ssize_t count = 0;
> +
> +       if (!df->profile->freq_table)
> +               return available_frequencies_show(d, attr, buf);
> +
> +       for (i = 0; i < df->profile->max_state; i++)
> +               count += scnprintf(&buf[count], (PAGE_SIZE - count - 2),
> +                                  "%u ", df->profile->freq_table[i]);
> +
> +       /* Truncate the trailing space */
> +       if (count)
> +               count--;
> +
> +       count += sprintf(&buf[count], "\n");
> +
> +       return count;
> +}
> +static DEVICE_ATTR_RO(possible_frequencies);
> +
>  static ssize_t trans_stat_show(struct device *dev,
>                                struct device_attribute *attr, char *buf)
>  {
> @@ -1041,6 +1066,7 @@ static struct attribute *devfreq_attrs[] = {
>         &dev_attr_available_governors.attr,
>         &dev_attr_cur_freq.attr,
>         &dev_attr_available_frequencies.attr,
> +       &dev_attr_possible_frequencies.attr,
>         &dev_attr_target_freq.attr,
>         &dev_attr_polling_interval.attr,
>         &dev_attr_min_freq.attr,
> --
> 1.8.2.1
>
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> hosted by The Linux Foundation
>
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-- 
MyungJoo Ham, Ph.D.
System S/W Lab, S/W Center, Samsung Electronicsÿôèº{.nÇ+‰·Ÿ®‰­†+%ŠËÿ±éݶ\x17¥Šwÿº{.nÇ+‰·¥Š{±þG«éÿŠ{ayº\x1dʇڙë,j\a­¢f£¢·hšïêÿ‘êçz_è®\x03(­éšŽŠÝ¢j"ú\x1a¶^[m§ÿÿ¾\a«þG«éÿ¢¸?™¨è­Ú&£ø§~á¶iO•æ¬z·švØ^\x14\x04\x1a¶^[m§ÿÿÃ\fÿ¶ìÿ¢¸?–I¥