Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932629Ab1ERAsQ (ORCPT ); Tue, 17 May 2011 20:48:16 -0400 Received: from mail-bw0-f46.google.com ([209.85.214.46]:36458 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932107Ab1ERAsP convert rfc822-to-8bit (ORCPT ); Tue, 17 May 2011 20:48:15 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:reply-to:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; b=hwq/JE9WSSU8OZ3WB5ymUvbB0OLOXAgKrQov6SKIJ/0t6RozjsnU+0XsCoqsEsaATh 498jBYf7JQT5U3RA28ewaizbRicajBisNS3MZJcGNbrqXSbQgQBygQSk9O4+Da8TCN3D q3BVNoZLZlYau40tql4sMHI6kI+GcM17uAc9k= MIME-Version: 1.0 Reply-To: myungjoo.ham@gmail.com In-Reply-To: <201105180039.56806.rjw@sisk.pl> References: <1305100723-29161-1-git-send-email-myungjoo.ham@samsung.com> <1305100723-29161-2-git-send-email-myungjoo.ham@samsung.com> <201105180039.56806.rjw@sisk.pl> Date: Wed, 18 May 2011 09:48:13 +0900 X-Google-Sender-Auth: 4-sVfoMuLYe2wS9IDD_ByPfQ2oc Message-ID: Subject: Re: [PATCH v2 2/3] PM / DEVFREQ: add example governors From: MyungJoo Ham To: "Rafael J. Wysocki" Cc: linux-pm@lists.linux-foundation.org, linux-kernel@vger.kernel.org, Greg Kroah-Hartman , Mark Brown , Jiejing Zhang , Pavel Machek , Colin Cross , Nishanth Menon , Thomas Gleixner , Len Brown , Kyungmin Park Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5615 Lines: 156 2011/5/18 Rafael J. Wysocki : > On Wednesday, May 11, 2011, MyungJoo Ham wrote: >> Three CPUFREQ-like governors are provided as examples. >> >> powersave: use the lowest frequency possible. The user (device) should >> set the polling_ms as 0 because polling is useless for this governor. >> >> performance: use the highest freqeuncy possible. The user (device) >> should set the polling_ms as 0 because polling is useless for this >> governor. >> >> simple_ondemand: simplified version of CPUFREQ's ONDEMAND governor. >> >> When a user updates OPP entries (enable/disable/add), OPP framework >> automatically notifies DEVFREQ to update operating frequency >> accordingly. Thus, DEVFREQ users (device drivers) do not need to update >> DEVFREQ manually with OPP entry updates or set polling_ms for powersave >> , performance, or any other "static" governors. > > Well, do you expect anyone to actually use them?  If not, it would make > more sense to put them into a doc. According to our experiences of DVFS(although this "DEVFREQ" is not applied to them, yet) in memory-bus and GPU, I expect most DEVFREQ users might use "simple_ondemand" and expect "powersave" and "performance" will probably mostly used while testing and debugging. ("userspace"-like governor would be also useful for that purpose, but I'd add it later) Cheers! - MyungJoo > > Thanks, > Rafael > > >> Signed-off-by: MyungJoo Ham >> Signed-off-by: Kyungmin Park >> --- >>  drivers/base/power/devfreq.c |   69 ++++++++++++++++++++++++++++++++++++++++++ >>  include/linux/devfreq.h      |    5 +++ >>  2 files changed, 74 insertions(+), 0 deletions(-) >> >> diff --git a/drivers/base/power/devfreq.c b/drivers/base/power/devfreq.c >> index 8e2e45b..251d761 100644 >> --- a/drivers/base/power/devfreq.c >> +++ b/drivers/base/power/devfreq.c >> @@ -351,3 +351,72 @@ static int __init devfreq_init(void) >>       return 0; >>  } >>  late_initcall(devfreq_init); >> + >> +static int devfreq_powersave_func(struct devfreq *df, >> +                               unsigned long *freq) >> +{ >> +     *freq = 0; /* devfreq_do will run "ceiling" to 0 */ >> +     return 0; >> +} >> + >> +struct devfreq_governor devfreq_powersave = { >> +     .get_target_freq = devfreq_powersave_func, >> +}; >> + >> +static int devfreq_performance_func(struct devfreq *df, >> +                                 unsigned long *freq) >> +{ >> +     *freq = UINT_MAX; /* devfreq_do will run "floor" */ >> +     return 0; >> +} >> + >> +struct devfreq_governor devfreq_performance = { >> +     .get_target_freq = devfreq_performance_func, >> +}; >> + >> +/* Constants for DevFreq-Simple-Ondemand (DFSO) */ >> +#define DFSO_UPTHRESHOLD     (90) >> +#define DFSO_DOWNDIFFERENCTIAL       (5) >> +static int devfreq_simple_ondemand_func(struct devfreq *df, >> +                                     unsigned long *freq) >> +{ >> +     struct devfreq_dev_status stat; >> +     int err = df->profile->get_dev_status(df->dev, &stat); >> +     unsigned long long a, b; >> + >> +     if (err) >> +             return err; >> + >> +     /* Set MAX if it's busy enough */ >> +     if (stat.busy_time * 100 > >> +         stat.total_time * DFSO_UPTHRESHOLD) { >> +             *freq = UINT_MAX; >> +             return 0; >> +     } >> + >> +     /* Set MAX if we do not know the initial frequency */ >> +     if (stat.current_frequency == 0) { >> +             *freq = UINT_MAX; >> +             return 0; >> +     } >> + >> +     /* Keep the current frequency */ >> +     if (stat.busy_time * 100 > >> +         stat.total_time * (DFSO_UPTHRESHOLD - DFSO_DOWNDIFFERENCTIAL)) { >> +             *freq = stat.current_frequency; >> +             return 0; >> +     } >> + >> +     /* Set the desired frequency based on the load */ >> +     a = (unsigned long long) stat.busy_time * stat.current_frequency; >> +     b = div_u64(a, stat.total_time); >> +     b *= 100; >> +     b = div_u64(b, (DFSO_UPTHRESHOLD - DFSO_DOWNDIFFERENCTIAL / 2)); >> +     *freq = (unsigned long) b; >> + >> +     return 0; >> +} >> + >> +struct devfreq_governor devfreq_simple_ondemand = { >> +     .get_target_freq = devfreq_simple_ondemand_func, >> +}; >> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h >> index d08e9f5..ec41ba6 100644 >> --- a/include/linux/devfreq.h >> +++ b/include/linux/devfreq.h >> @@ -81,6 +81,11 @@ extern int devfreq_add_device(struct device *dev, >>  extern int devfreq_remove_device(struct device *dev); >>  extern int devfreq_update(struct device *dev, bool may_not_exist); >>  extern int devfreq_tickle_device(struct device *dev, unsigned long duration_ms); >> + >> +extern struct devfreq_governor devfreq_powersave; >> +extern struct devfreq_governor devfreq_performance; >> +extern struct devfreq_governor devfreq_simple_ondemand; >> + >>  #else /* !CONFIG_PM_DEVFREQ */ >>  static int devfreq_add_device(struct device *dev, >>                          struct devfreq_dev_profile *profile, >> > > -- MyungJoo Ham (함명주), Ph.D. Mobile Software Platform Lab, Digital Media and Communications (DMC) Business Samsung Electronics cell: 82-10-6714-2858 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/