From mboxrd@z Thu Jan  1 00:00:00 1970
From: MyungJoo Ham <myungjoo.ham@samsung.com>
Subject: RE: Re: [PATCH] devfreq: do not ignore errors during store min, max
 frequency
Date: Thu, 27 Apr 2017 23:41:23 +0000
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To: Lukasz Luba <lukasz.luba@arm.com>, "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>
Cc: Chanwoo Choi <cw00.choi@samsung.com>, Kyungmin Park <kyungmin.park@samsung.com>

> >
> > ...
> >
> >> +	ret = devfreq_get_freq_level(df, value);
> >> +	if (ret < 0) {
> >> +		dev_warn(dev, "Storing min freq failed with (%d) error\n", ret);
> >> +		goto unlock;
> >> +	}
> >> +
> >
> > This is not good.
> >
> > For a device that supports [ 100, 400, 800, 1000 ] MHz,
> > saying "min = 200 Mhz" or "max = 600 MHz" shouldn't be prohibited.
> >
> > Those functions are to express lower bound and upper bound, not to
> > designate the exact operating frequencies.
> 
> Would it be possible to convince you to store a
> 'posible/valid frequency' (from OPP) in that value?
> Governors (like simpleondemand) and drivers use it with the flags.
> It would be useful for thermal subsystem. It could have the max/min for 
> the devfreq device.
> 
> I could prepare a patch which sets the freq from OPP respecting
> rounding up/down based on 'devfreq_recommended_opp()'.
> 
> Regards,
> Lukasz

Before talking about implementation detail,
what's the benefit of what you are suggesting?

What's the scenario that you cannot do with the current system
while you can do with what you suggest?

Why do you need rounded (OPP-enabled) max/min values?
Why unrounded (lower/upper limits) max/min values cannot do what you want?


Cheers,
MyungJoo


ps. I'll be away from the network for about 10 days after few hours.