cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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governor_simpleondemand.c (3373B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/*
      3 *  linux/drivers/devfreq/governor_simpleondemand.c
      4 *
      5 *  Copyright (C) 2011 Samsung Electronics
      6 *	MyungJoo Ham <myungjoo.ham@samsung.com>
      7 */
      8
      9#include <linux/errno.h>
     10#include <linux/module.h>
     11#include <linux/devfreq.h>
     12#include <linux/math64.h>
     13#include "governor.h"
     14
     15/* Default constants for DevFreq-Simple-Ondemand (DFSO) */
     16#define DFSO_UPTHRESHOLD	(90)
     17#define DFSO_DOWNDIFFERENCTIAL	(5)
     18static int devfreq_simple_ondemand_func(struct devfreq *df,
     19					unsigned long *freq)
     20{
     21	int err;
     22	struct devfreq_dev_status *stat;
     23	unsigned long long a, b;
     24	unsigned int dfso_upthreshold = DFSO_UPTHRESHOLD;
     25	unsigned int dfso_downdifferential = DFSO_DOWNDIFFERENCTIAL;
     26	struct devfreq_simple_ondemand_data *data = df->data;
     27
     28	err = devfreq_update_stats(df);
     29	if (err)
     30		return err;
     31
     32	stat = &df->last_status;
     33
     34	if (data) {
     35		if (data->upthreshold)
     36			dfso_upthreshold = data->upthreshold;
     37		if (data->downdifferential)
     38			dfso_downdifferential = data->downdifferential;
     39	}
     40	if (dfso_upthreshold > 100 ||
     41	    dfso_upthreshold < dfso_downdifferential)
     42		return -EINVAL;
     43
     44	/* Assume MAX if it is going to be divided by zero */
     45	if (stat->total_time == 0) {
     46		*freq = DEVFREQ_MAX_FREQ;
     47		return 0;
     48	}
     49
     50	/* Prevent overflow */
     51	if (stat->busy_time >= (1 << 24) || stat->total_time >= (1 << 24)) {
     52		stat->busy_time >>= 7;
     53		stat->total_time >>= 7;
     54	}
     55
     56	/* Set MAX if it's busy enough */
     57	if (stat->busy_time * 100 >
     58	    stat->total_time * dfso_upthreshold) {
     59		*freq = DEVFREQ_MAX_FREQ;
     60		return 0;
     61	}
     62
     63	/* Set MAX if we do not know the initial frequency */
     64	if (stat->current_frequency == 0) {
     65		*freq = DEVFREQ_MAX_FREQ;
     66		return 0;
     67	}
     68
     69	/* Keep the current frequency */
     70	if (stat->busy_time * 100 >
     71	    stat->total_time * (dfso_upthreshold - dfso_downdifferential)) {
     72		*freq = stat->current_frequency;
     73		return 0;
     74	}
     75
     76	/* Set the desired frequency based on the load */
     77	a = stat->busy_time;
     78	a *= stat->current_frequency;
     79	b = div_u64(a, stat->total_time);
     80	b *= 100;
     81	b = div_u64(b, (dfso_upthreshold - dfso_downdifferential / 2));
     82	*freq = (unsigned long) b;
     83
     84	return 0;
     85}
     86
     87static int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
     88				unsigned int event, void *data)
     89{
     90	switch (event) {
     91	case DEVFREQ_GOV_START:
     92		devfreq_monitor_start(devfreq);
     93		break;
     94
     95	case DEVFREQ_GOV_STOP:
     96		devfreq_monitor_stop(devfreq);
     97		break;
     98
     99	case DEVFREQ_GOV_UPDATE_INTERVAL:
    100		devfreq_update_interval(devfreq, (unsigned int *)data);
    101		break;
    102
    103	case DEVFREQ_GOV_SUSPEND:
    104		devfreq_monitor_suspend(devfreq);
    105		break;
    106
    107	case DEVFREQ_GOV_RESUME:
    108		devfreq_monitor_resume(devfreq);
    109		break;
    110
    111	default:
    112		break;
    113	}
    114
    115	return 0;
    116}
    117
    118static struct devfreq_governor devfreq_simple_ondemand = {
    119	.name = DEVFREQ_GOV_SIMPLE_ONDEMAND,
    120	.attrs = DEVFREQ_GOV_ATTR_POLLING_INTERVAL
    121		| DEVFREQ_GOV_ATTR_TIMER,
    122	.get_target_freq = devfreq_simple_ondemand_func,
    123	.event_handler = devfreq_simple_ondemand_handler,
    124};
    125
    126static int __init devfreq_simple_ondemand_init(void)
    127{
    128	return devfreq_add_governor(&devfreq_simple_ondemand);
    129}
    130subsys_initcall(devfreq_simple_ondemand_init);
    131
    132static void __exit devfreq_simple_ondemand_exit(void)
    133{
    134	int ret;
    135
    136	ret = devfreq_remove_governor(&devfreq_simple_ondemand);
    137	if (ret)
    138		pr_err("%s: failed remove governor %d\n", __func__, ret);
    139
    140	return;
    141}
    142module_exit(devfreq_simple_ondemand_exit);
    143MODULE_LICENSE("GPL");