95 lines
2.4 KiB
C
95 lines
2.4 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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unsigned long max = (df->max_freq) ? df->max_freq : UINT_MAX;
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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 = 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 = 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 = 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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if (df->min_freq && *freq < df->min_freq)
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*freq = df->min_freq;
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if (df->max_freq && *freq > df->max_freq)
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*freq = df->max_freq;
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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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