Commit | Line | Data |
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d0a533b1 WD |
1 | /* |
2 | * Delay loops based on the OpenRISC implementation. | |
3 | * | |
4 | * Copyright (C) 2012 ARM Limited | |
5 | * | |
6 | * This program is free software; you can redistribute it and/or modify | |
7 | * it under the terms of the GNU General Public License version 2 as | |
8 | * published by the Free Software Foundation. | |
9 | * | |
10 | * This program is distributed in the hope that it will be useful, | |
11 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
13 | * GNU General Public License for more details. | |
14 | * | |
15 | * You should have received a copy of the GNU General Public License | |
16 | * along with this program; if not, write to the Free Software | |
17 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA | |
18 | * | |
19 | * Author: Will Deacon <will.deacon@arm.com> | |
20 | */ | |
21 | ||
5930c1a1 | 22 | #include <linux/clocksource.h> |
d0a533b1 WD |
23 | #include <linux/delay.h> |
24 | #include <linux/init.h> | |
25 | #include <linux/kernel.h> | |
26 | #include <linux/module.h> | |
27 | #include <linux/timex.h> | |
28 | ||
29 | /* | |
30 | * Default to the loop-based delay implementation. | |
31 | */ | |
7619751f | 32 | struct arm_delay_ops arm_delay_ops __ro_after_init = { |
d0a533b1 WD |
33 | .delay = __loop_delay, |
34 | .const_udelay = __loop_const_udelay, | |
35 | .udelay = __loop_udelay, | |
36 | }; | |
37 | ||
56942fec JA |
38 | static const struct delay_timer *delay_timer; |
39 | static bool delay_calibrated; | |
5930c1a1 | 40 | static u64 delay_res; |
56942fec JA |
41 | |
42 | int read_current_timer(unsigned long *timer_val) | |
43 | { | |
44 | if (!delay_timer) | |
45 | return -ENXIO; | |
46 | ||
47 | *timer_val = delay_timer->read_current_timer(); | |
48 | return 0; | |
49 | } | |
f3accb12 | 50 | EXPORT_SYMBOL_GPL(read_current_timer); |
56942fec | 51 | |
5930c1a1 PDS |
52 | static inline u64 cyc_to_ns(u64 cyc, u32 mult, u32 shift) |
53 | { | |
54 | return (cyc * mult) >> shift; | |
55 | } | |
56 | ||
d0a533b1 WD |
57 | static void __timer_delay(unsigned long cycles) |
58 | { | |
59 | cycles_t start = get_cycles(); | |
60 | ||
61 | while ((get_cycles() - start) < cycles) | |
62 | cpu_relax(); | |
63 | } | |
64 | ||
65 | static void __timer_const_udelay(unsigned long xloops) | |
66 | { | |
67 | unsigned long long loops = xloops; | |
6f3d90e5 | 68 | loops *= arm_delay_ops.ticks_per_jiffy; |
d0a533b1 WD |
69 | __timer_delay(loops >> UDELAY_SHIFT); |
70 | } | |
71 | ||
72 | static void __timer_udelay(unsigned long usecs) | |
73 | { | |
74 | __timer_const_udelay(usecs * UDELAY_MULT); | |
75 | } | |
76 | ||
56942fec | 77 | void __init register_current_timer_delay(const struct delay_timer *timer) |
d0a533b1 | 78 | { |
5930c1a1 PDS |
79 | u32 new_mult, new_shift; |
80 | u64 res; | |
81 | ||
82 | clocks_calc_mult_shift(&new_mult, &new_shift, timer->freq, | |
83 | NSEC_PER_SEC, 3600); | |
84 | res = cyc_to_ns(1ULL, new_mult, new_shift); | |
85 | ||
57ca654b RK |
86 | if (res > 1000) { |
87 | pr_err("Ignoring delay timer %ps, which has insufficient resolution of %lluns\n", | |
88 | timer, res); | |
89 | return; | |
90 | } | |
91 | ||
5930c1a1 PDS |
92 | if (!delay_calibrated && (!delay_res || (res < delay_res))) { |
93 | pr_info("Switching to timer-based delay loop, resolution %lluns\n", res); | |
56942fec JA |
94 | delay_timer = timer; |
95 | lpj_fine = timer->freq / HZ; | |
5930c1a1 | 96 | delay_res = res; |
6f3d90e5 WD |
97 | |
98 | /* cpufreq may scale loops_per_jiffy, so keep a private copy */ | |
99 | arm_delay_ops.ticks_per_jiffy = lpj_fine; | |
56942fec JA |
100 | arm_delay_ops.delay = __timer_delay; |
101 | arm_delay_ops.const_udelay = __timer_const_udelay; | |
102 | arm_delay_ops.udelay = __timer_udelay; | |
56942fec JA |
103 | } else { |
104 | pr_info("Ignoring duplicate/late registration of read_current_timer delay\n"); | |
105 | } | |
d0a533b1 WD |
106 | } |
107 | ||
8bd26e3a | 108 | unsigned long calibrate_delay_is_known(void) |
d0a533b1 | 109 | { |
56942fec | 110 | delay_calibrated = true; |
d0a533b1 WD |
111 | return lpj_fine; |
112 | } | |
5930c1a1 PDS |
113 | |
114 | void calibration_delay_done(void) | |
115 | { | |
116 | delay_calibrated = true; | |
117 | } |