1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3 * (C) Copyright 2013
4 * David Feng <fenghua@phytium.com.cn>
5 */
6
7 #include <bootstage.h>
8 #include <command.h>
9 #include <time.h>
10 #include <asm/global_data.h>
11 #include <asm/system.h>
12 #include <linux/bitops.h>
13
14 DECLARE_GLOBAL_DATA_PTR;
15
16 /*
17 * Generic timer implementation of get_tbclk()
18 */
get_tbclk(void)19 unsigned long notrace get_tbclk(void)
20 {
21 unsigned long cntfrq;
22 asm volatile("mrs %0, cntfrq_el0" : "=r" (cntfrq));
23 return cntfrq;
24 }
25
26 #ifdef CONFIG_SYS_FSL_ERRATUM_A008585
27 /*
28 * FSL erratum A-008585 says that the ARM generic timer counter "has the
29 * potential to contain an erroneous value for a small number of core
30 * clock cycles every time the timer value changes".
31 * This sometimes leads to a consecutive counter read returning a lower
32 * value than the previous one, thus reporting the time to go backwards.
33 * The workaround is to read the counter twice and only return when the value
34 * was the same in both reads.
35 * Assumes that the CPU runs in much higher frequency than the timer.
36 */
timer_read_counter(void)37 unsigned long timer_read_counter(void)
38 {
39 unsigned long cntpct;
40 unsigned long temp;
41
42 isb();
43 asm volatile("mrs %0, cntpct_el0" : "=r" (cntpct));
44 asm volatile("mrs %0, cntpct_el0" : "=r" (temp));
45 while (temp != cntpct) {
46 asm volatile("mrs %0, cntpct_el0" : "=r" (cntpct));
47 asm volatile("mrs %0, cntpct_el0" : "=r" (temp));
48 }
49
50 return cntpct;
51 }
52 #elif CONFIG_SUNXI_A64_TIMER_ERRATUM
53 /*
54 * This erratum sometimes flips the lower 11 bits of the counter value
55 * to all 0's or all 1's, leading to jumps forwards or backwards.
56 * Backwards jumps might be interpreted all roll-overs and be treated as
57 * huge jumps forward.
58 * The workaround is to check whether the lower 11 bits of the counter are
59 * all 0 or all 1, then discard this value and read again.
60 * This occasionally discards valid values, but will catch all erroneous
61 * reads and fixes the problem reliably. Also this mostly requires only a
62 * single read, so does not have any significant overhead.
63 * The algorithm was conceived by Samuel Holland.
64 */
timer_read_counter(void)65 unsigned long timer_read_counter(void)
66 {
67 unsigned long cntpct;
68
69 isb();
70 do {
71 asm volatile("mrs %0, cntpct_el0" : "=r" (cntpct));
72 } while (((cntpct + 1) & GENMASK(10, 0)) <= 1);
73
74 return cntpct;
75 }
76 #else
77 /*
78 * timer_read_counter() using the Arm Generic Timer (aka arch timer).
79 */
timer_read_counter(void)80 unsigned long notrace timer_read_counter(void)
81 {
82 unsigned long cntpct;
83
84 isb();
85 asm volatile("mrs %0, cntpct_el0" : "=r" (cntpct));
86
87 return cntpct;
88 }
89 #endif
90
get_ticks(void)91 uint64_t notrace get_ticks(void)
92 {
93 unsigned long ticks = timer_read_counter();
94
95 gd->arch.tbl = ticks;
96
97 return ticks;
98 }
99
usec2ticks(unsigned long usec)100 unsigned long usec2ticks(unsigned long usec)
101 {
102 ulong ticks;
103 if (usec < 1000)
104 ticks = ((usec * (get_tbclk()/1000)) + 500) / 1000;
105 else
106 ticks = ((usec / 10) * (get_tbclk() / 100000));
107
108 return ticks;
109 }
110
timer_get_boot_us(void)111 ulong timer_get_boot_us(void)
112 {
113 u64 val = get_ticks() * 1000000;
114
115 return val / get_tbclk();
116 }
117
118 #if CONFIG_IS_ENABLED(ARMV8_UDELAY_EVENT_STREAM)
__udelay(unsigned long usec)119 void __udelay(unsigned long usec)
120 {
121 u64 target = get_ticks() + usec_to_tick(usec);
122
123 /* At EL2 or above, use the event stream to avoid polling CNTPCT_EL0 so often */
124 if (current_el() >= 2) {
125 u32 cnthctl_val;
126 const u8 event_period = 0x7;
127
128 asm volatile("mrs %0, cnthctl_el2" : "=r" (cnthctl_val));
129 asm volatile("msr cnthctl_el2, %0" : : "r"
130 (cnthctl_val | CNTHCTL_EL2_EVNT_EN | CNTHCTL_EL2_EVNT_I(event_period)));
131
132 while (get_ticks() + (1ULL << event_period) <= target)
133 wfe();
134
135 /* Reset the event stream */
136 asm volatile("msr cnthctl_el2, %0" : : "r" (cnthctl_val));
137 }
138
139 /* Fall back to polling CNTPCT_EL0 */
140 while (get_ticks() <= target)
141 ;
142 }
143 #endif
144