1 /* 2 * linux/drivers/devfreq/governor_simpleondemand.c 3 * 4 * Copyright (C) 2011 Samsung Electronics 5 * MyungJoo Ham <myungjoo.ham@samsung.com> 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License version 2 as 9 * published by the Free Software Foundation. 10 */ 11 12 #include <linux/errno.h> 13 #include <linux/devfreq.h> 14 #include <linux/math64.h> 15 16 /* Default constants for DevFreq-Simple-Ondemand (DFSO) */ 17 #define DFSO_UPTHRESHOLD (90) 18 #define DFSO_DOWNDIFFERENCTIAL (5) 19 static int devfreq_simple_ondemand_func(struct devfreq *df, 20 unsigned long *freq) 21 { 22 struct devfreq_dev_status stat; 23 int err = df->profile->get_dev_status(df->dev.parent, &stat); 24 unsigned long long a, b; 25 unsigned int dfso_upthreshold = DFSO_UPTHRESHOLD; 26 unsigned int dfso_downdifferential = DFSO_DOWNDIFFERENCTIAL; 27 struct devfreq_simple_ondemand_data *data = df->data; 28 29 if (err) 30 return err; 31 32 if (data) { 33 if (data->upthreshold) 34 dfso_upthreshold = data->upthreshold; 35 if (data->downdifferential) 36 dfso_downdifferential = data->downdifferential; 37 } 38 if (dfso_upthreshold > 100 || 39 dfso_upthreshold < dfso_downdifferential) 40 return -EINVAL; 41 42 /* Assume MAX if it is going to be divided by zero */ 43 if (stat.total_time == 0) { 44 *freq = UINT_MAX; 45 return 0; 46 } 47 48 /* Prevent overflow */ 49 if (stat.busy_time >= (1 << 24) || stat.total_time >= (1 << 24)) { 50 stat.busy_time >>= 7; 51 stat.total_time >>= 7; 52 } 53 54 /* Set MAX if it's busy enough */ 55 if (stat.busy_time * 100 > 56 stat.total_time * dfso_upthreshold) { 57 *freq = UINT_MAX; 58 return 0; 59 } 60 61 /* Set MAX if we do not know the initial frequency */ 62 if (stat.current_frequency == 0) { 63 *freq = UINT_MAX; 64 return 0; 65 } 66 67 /* Keep the current frequency */ 68 if (stat.busy_time * 100 > 69 stat.total_time * (dfso_upthreshold - dfso_downdifferential)) { 70 *freq = stat.current_frequency; 71 return 0; 72 } 73 74 /* Set the desired frequency based on the load */ 75 a = stat.busy_time; 76 a *= stat.current_frequency; 77 b = div_u64(a, stat.total_time); 78 b *= 100; 79 b = div_u64(b, (dfso_upthreshold - dfso_downdifferential / 2)); 80 *freq = (unsigned long) b; 81 82 return 0; 83 } 84 85 const struct devfreq_governor devfreq_simple_ondemand = { 86 .name = "simple_ondemand", 87 .get_target_freq = devfreq_simple_ondemand_func, 88 }; 89