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