linux-kernel - Re: Re: [PATCH 6/6] PM / devfreq: Set the min_freq and max

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Message-id: <1427563269.125721448263260488.JavaMail.weblogic@epmlwas06a>
Date:	Mon, 23 Nov 2015 07:21:00 +0000 (GMT)
From:	MyungJoo Ham <myungjoo.ham@...sung.com>
To:	최찬우 <cw00.choi@...sung.com>,
	박경민 <kyungmin.park@...sung.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
Subject: Re: Re: [PATCH 6/6] PM / devfreq: Set the min_freq and max_freq of
 devfreq device

[]
> > 
> > The value 0 is used for min/max_freq to declare
> > that min/max_freq is deactivated. Therefore, it is not
> > required to do so; they are not intended to show the hardware
> > configuration as well.
> 
> This case consider the devfreq device using OPP because devfreq_set_freq_table()
> get the number of OPP entry in OPP list before setting the min_freq/max_freq.
> If the devfreq device don't use the OPP entry, devfreq_set_freq_table()
> will return without any operation.
> 
> IMHO, when devfreq device uses the OPP table including the frequency,
> min_freq/max_freq should show the correct value as CPUFREQ framework.
> 

The side effect of this patch shows up when opp_disable() and opp_enable()
are used.

For example,
1. dev->opp_disable(2GHz); /* 2GHz is the fastest and 1.6 is the second */
2. init devfreq of dev; /* setting max_freq @ 1.6G by this patch */
3. dev->opp_enable(2GHz);
4. 2GHz is still not active because max_freq is now 1.6GHz.

Cheers,
MyungJoo.