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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delay.c (2452B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/*
      3 * Delay loops based on the OpenRISC implementation.
      4 *
      5 * Copyright (C) 2012 ARM Limited
      6 *
      7 * Author: Will Deacon <will.deacon@arm.com>
      8 */
      9
     10#include <linux/clocksource.h>
     11#include <linux/delay.h>
     12#include <linux/init.h>
     13#include <linux/kernel.h>
     14#include <linux/module.h>
     15#include <linux/timex.h>
     16
     17/*
     18 * Default to the loop-based delay implementation.
     19 */
     20struct arm_delay_ops arm_delay_ops __ro_after_init = {
     21	.delay		= __loop_delay,
     22	.const_udelay	= __loop_const_udelay,
     23	.udelay		= __loop_udelay,
     24};
     25
     26static const struct delay_timer *delay_timer;
     27static bool delay_calibrated;
     28static u64 delay_res;
     29
     30int read_current_timer(unsigned long *timer_val)
     31{
     32	if (!delay_timer)
     33		return -ENXIO;
     34
     35	*timer_val = delay_timer->read_current_timer();
     36	return 0;
     37}
     38EXPORT_SYMBOL_GPL(read_current_timer);
     39
     40static inline u64 cyc_to_ns(u64 cyc, u32 mult, u32 shift)
     41{
     42	return (cyc * mult) >> shift;
     43}
     44
     45static void __timer_delay(unsigned long cycles)
     46{
     47	cycles_t start = get_cycles();
     48
     49	while ((get_cycles() - start) < cycles)
     50		cpu_relax();
     51}
     52
     53static void __timer_const_udelay(unsigned long xloops)
     54{
     55	unsigned long long loops = xloops;
     56	loops *= arm_delay_ops.ticks_per_jiffy;
     57	__timer_delay(loops >> UDELAY_SHIFT);
     58}
     59
     60static void __timer_udelay(unsigned long usecs)
     61{
     62	__timer_const_udelay(usecs * UDELAY_MULT);
     63}
     64
     65void __init register_current_timer_delay(const struct delay_timer *timer)
     66{
     67	u32 new_mult, new_shift;
     68	u64 res;
     69
     70	clocks_calc_mult_shift(&new_mult, &new_shift, timer->freq,
     71			       NSEC_PER_SEC, 3600);
     72	res = cyc_to_ns(1ULL, new_mult, new_shift);
     73
     74	if (res > 1000) {
     75		pr_err("Ignoring delay timer %ps, which has insufficient resolution of %lluns\n",
     76			timer, res);
     77		return;
     78	}
     79
     80	if (!delay_calibrated && (!delay_res || (res < delay_res))) {
     81		pr_info("Switching to timer-based delay loop, resolution %lluns\n", res);
     82		delay_timer			= timer;
     83		lpj_fine			= timer->freq / HZ;
     84		delay_res			= res;
     85
     86		/* cpufreq may scale loops_per_jiffy, so keep a private copy */
     87		arm_delay_ops.ticks_per_jiffy	= lpj_fine;
     88		arm_delay_ops.delay		= __timer_delay;
     89		arm_delay_ops.const_udelay	= __timer_const_udelay;
     90		arm_delay_ops.udelay		= __timer_udelay;
     91	} else {
     92		pr_info("Ignoring duplicate/late registration of read_current_timer delay\n");
     93	}
     94}
     95
     96unsigned long calibrate_delay_is_known(void)
     97{
     98	delay_calibrated = true;
     99	return lpj_fine;
    100}
    101
    102void calibration_delay_done(void)
    103{
    104	delay_calibrated = true;
    105}