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Four 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. userspace: use the user specified frequency stored at devfreq.user_set_freq. With sysfs support in the following patch, a user may set the value with the sysfs interface. 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, userspace, or any other "static" governors. Note that these are given only as basic examples for governors and any devices with devfreq may implement their own governors with the drivers and use them. Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com> Reviewed-by: Mike Turquette <mturquette@ti.com> Acked-by: Kevin Hilman <khilman@ti.com> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
89 lines
2.3 KiB
C
89 lines
2.3 KiB
C
/*
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* linux/drivers/devfreq/governor_simpleondemand.c
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*
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* Copyright (C) 2011 Samsung Electronics
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* MyungJoo Ham <myungjoo.ham@samsung.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/errno.h>
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#include <linux/devfreq.h>
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#include <linux/math64.h>
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/* Default constants for DevFreq-Simple-Ondemand (DFSO) */
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#define DFSO_UPTHRESHOLD (90)
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#define DFSO_DOWNDIFFERENCTIAL (5)
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static int devfreq_simple_ondemand_func(struct devfreq *df,
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unsigned long *freq)
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{
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struct devfreq_dev_status stat;
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int err = df->profile->get_dev_status(df->dev.parent, &stat);
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unsigned long long a, b;
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unsigned int dfso_upthreshold = DFSO_UPTHRESHOLD;
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unsigned int dfso_downdifferential = DFSO_DOWNDIFFERENCTIAL;
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struct devfreq_simple_ondemand_data *data = df->data;
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if (err)
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return err;
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if (data) {
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if (data->upthreshold)
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dfso_upthreshold = data->upthreshold;
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if (data->downdifferential)
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dfso_downdifferential = data->downdifferential;
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}
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if (dfso_upthreshold > 100 ||
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dfso_upthreshold < dfso_downdifferential)
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return -EINVAL;
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/* Assume MAX if it is going to be divided by zero */
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if (stat.total_time == 0) {
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*freq = UINT_MAX;
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return 0;
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}
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/* Prevent overflow */
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if (stat.busy_time >= (1 << 24) || stat.total_time >= (1 << 24)) {
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stat.busy_time >>= 7;
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stat.total_time >>= 7;
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}
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/* Set MAX if it's busy enough */
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if (stat.busy_time * 100 >
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stat.total_time * dfso_upthreshold) {
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*freq = UINT_MAX;
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return 0;
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}
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/* Set MAX if we do not know the initial frequency */
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if (stat.current_frequency == 0) {
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*freq = UINT_MAX;
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return 0;
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}
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/* Keep the current frequency */
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if (stat.busy_time * 100 >
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stat.total_time * (dfso_upthreshold - dfso_downdifferential)) {
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*freq = stat.current_frequency;
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return 0;
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}
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/* Set the desired frequency based on the load */
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a = stat.busy_time;
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a *= stat.current_frequency;
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b = div_u64(a, stat.total_time);
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b *= 100;
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b = div_u64(b, (dfso_upthreshold - dfso_downdifferential / 2));
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*freq = (unsigned long) b;
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return 0;
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}
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const struct devfreq_governor devfreq_simple_ondemand = {
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.name = "simple_ondemand",
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.get_target_freq = devfreq_simple_ondemand_func,
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};
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