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105 lines
2.4 KiB
105 lines
2.4 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* Delay loops based on the OpenRISC implementation. |
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* |
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* Copyright (C) 2012 ARM Limited |
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* |
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* Author: Will Deacon <[email protected]> |
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*/ |
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#include <linux/clocksource.h> |
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#include <linux/delay.h> |
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#include <linux/init.h> |
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#include <linux/kernel.h> |
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#include <linux/module.h> |
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#include <linux/timex.h> |
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/* |
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* Default to the loop-based delay implementation. |
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*/ |
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struct arm_delay_ops arm_delay_ops __ro_after_init = { |
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.delay = __loop_delay, |
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.const_udelay = __loop_const_udelay, |
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.udelay = __loop_udelay, |
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}; |
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static const struct delay_timer *delay_timer; |
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static bool delay_calibrated; |
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static u64 delay_res; |
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int read_current_timer(unsigned long *timer_val) |
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{ |
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if (!delay_timer) |
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return -ENXIO; |
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*timer_val = delay_timer->read_current_timer(); |
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return 0; |
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} |
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EXPORT_SYMBOL_GPL(read_current_timer); |
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static inline u64 cyc_to_ns(u64 cyc, u32 mult, u32 shift) |
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{ |
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return (cyc * mult) >> shift; |
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} |
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static void __timer_delay(unsigned long cycles) |
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{ |
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cycles_t start = get_cycles(); |
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while ((get_cycles() - start) < cycles) |
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cpu_relax(); |
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} |
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static void __timer_const_udelay(unsigned long xloops) |
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{ |
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unsigned long long loops = xloops; |
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loops *= arm_delay_ops.ticks_per_jiffy; |
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__timer_delay(loops >> UDELAY_SHIFT); |
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} |
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static void __timer_udelay(unsigned long usecs) |
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{ |
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__timer_const_udelay(usecs * UDELAY_MULT); |
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} |
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void __init register_current_timer_delay(const struct delay_timer *timer) |
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{ |
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u32 new_mult, new_shift; |
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u64 res; |
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clocks_calc_mult_shift(&new_mult, &new_shift, timer->freq, |
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NSEC_PER_SEC, 3600); |
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res = cyc_to_ns(1ULL, new_mult, new_shift); |
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if (res > 1000) { |
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pr_err("Ignoring delay timer %ps, which has insufficient resolution of %lluns\n", |
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timer, res); |
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return; |
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} |
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if (!delay_calibrated && (!delay_res || (res < delay_res))) { |
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pr_info("Switching to timer-based delay loop, resolution %lluns\n", res); |
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delay_timer = timer; |
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lpj_fine = timer->freq / HZ; |
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delay_res = res; |
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/* cpufreq may scale loops_per_jiffy, so keep a private copy */ |
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arm_delay_ops.ticks_per_jiffy = lpj_fine; |
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arm_delay_ops.delay = __timer_delay; |
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arm_delay_ops.const_udelay = __timer_const_udelay; |
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arm_delay_ops.udelay = __timer_udelay; |
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} else { |
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pr_info("Ignoring duplicate/late registration of read_current_timer delay\n"); |
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} |
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} |
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unsigned long calibrate_delay_is_known(void) |
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{ |
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delay_calibrated = true; |
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return lpj_fine; |
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} |
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void calibration_delay_done(void) |
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{ |
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delay_calibrated = true; |
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}
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