1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * OpenRISC time.c
4 *
5 * Linux architectural port borrowing liberally from similar works of
6 * others. All original copyrights apply as per the original source
7 * declaration.
8 *
9 * Modifications for the OpenRISC architecture:
10 * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
11 */
12
13 #include <linux/kernel.h>
14 #include <linux/time.h>
15 #include <linux/timex.h>
16 #include <linux/interrupt.h>
17 #include <linux/ftrace.h>
18
19 #include <linux/clocksource.h>
20 #include <linux/clockchips.h>
21 #include <linux/irq.h>
22 #include <linux/io.h>
23 #include <linux/of_clk.h>
24
25 #include <asm/cpuinfo.h>
26 #include <asm/time.h>
27
28 /* Test the timer ticks to count, used in sync routine */
openrisc_timer_set(unsigned long count)29 inline void openrisc_timer_set(unsigned long count)
30 {
31 mtspr(SPR_TTCR, count);
32 }
33
34 /* Set the timer to trigger in delta cycles */
openrisc_timer_set_next(unsigned long delta)35 inline void openrisc_timer_set_next(unsigned long delta)
36 {
37 u32 c;
38
39 /* Read 32-bit counter value, add delta, mask off the low 28 bits.
40 * We're guaranteed delta won't be bigger than 28 bits because the
41 * generic timekeeping code ensures that for us.
42 */
43 c = mfspr(SPR_TTCR);
44 c += delta;
45 c &= SPR_TTMR_TP;
46
47 /* Set counter and enable interrupt.
48 * Keep timer in continuous mode always.
49 */
50 mtspr(SPR_TTMR, SPR_TTMR_CR | SPR_TTMR_IE | c);
51 }
52
openrisc_timer_set_next_event(unsigned long delta,struct clock_event_device * dev)53 static int openrisc_timer_set_next_event(unsigned long delta,
54 struct clock_event_device *dev)
55 {
56 openrisc_timer_set_next(delta);
57 return 0;
58 }
59
60 /* This is the clock event device based on the OR1K tick timer.
61 * As the timer is being used as a continuous clock-source (required for HR
62 * timers) we cannot enable the PERIODIC feature. The tick timer can run using
63 * one-shot events, so no problem.
64 */
65 static DEFINE_PER_CPU(struct clock_event_device, clockevent_openrisc_timer);
66
openrisc_clockevent_init(void)67 void openrisc_clockevent_init(void)
68 {
69 unsigned int cpu = smp_processor_id();
70 struct clock_event_device *evt =
71 &per_cpu(clockevent_openrisc_timer, cpu);
72 struct cpuinfo_or1k *cpuinfo = &cpuinfo_or1k[cpu];
73
74 mtspr(SPR_TTMR, SPR_TTMR_CR);
75
76 #ifdef CONFIG_SMP
77 evt->broadcast = tick_broadcast;
78 #endif
79 evt->name = "openrisc_timer_clockevent",
80 evt->features = CLOCK_EVT_FEAT_ONESHOT,
81 evt->rating = 300,
82 evt->set_next_event = openrisc_timer_set_next_event,
83
84 evt->cpumask = cpumask_of(cpu);
85
86 /* We only have 28 bits */
87 clockevents_config_and_register(evt, cpuinfo->clock_frequency,
88 100, 0x0fffffff);
89
90 }
91
timer_ack(void)92 static inline void timer_ack(void)
93 {
94 /* Clear the IP bit and disable further interrupts */
95 /* This can be done very simply... we just need to keep the timer
96 running, so just maintain the CR bits while clearing the rest
97 of the register
98 */
99 mtspr(SPR_TTMR, SPR_TTMR_CR);
100 }
101
102 /*
103 * The timer interrupt is mostly handled in generic code nowadays... this
104 * function just acknowledges the interrupt and fires the event handler that
105 * has been set on the clockevent device by the generic time management code.
106 *
107 * This function needs to be called by the timer exception handler and that's
108 * all the exception handler needs to do.
109 */
110
timer_interrupt(struct pt_regs * regs)111 irqreturn_t __irq_entry timer_interrupt(struct pt_regs *regs)
112 {
113 struct pt_regs *old_regs = set_irq_regs(regs);
114 unsigned int cpu = smp_processor_id();
115 struct clock_event_device *evt =
116 &per_cpu(clockevent_openrisc_timer, cpu);
117
118 timer_ack();
119
120 /*
121 * update_process_times() expects us to have called irq_enter().
122 */
123 irq_enter();
124 evt->event_handler(evt);
125 irq_exit();
126
127 set_irq_regs(old_regs);
128
129 return IRQ_HANDLED;
130 }
131
132 /*
133 * Clocksource: Based on OpenRISC timer/counter
134 *
135 * This sets up the OpenRISC Tick Timer as a clock source. The tick timer
136 * is 32 bits wide and runs at the CPU clock frequency.
137 */
openrisc_timer_read(struct clocksource * cs)138 static u64 openrisc_timer_read(struct clocksource *cs)
139 {
140 return (u64) mfspr(SPR_TTCR);
141 }
142
143 static struct clocksource openrisc_timer = {
144 .name = "openrisc_timer",
145 .rating = 200,
146 .read = openrisc_timer_read,
147 .mask = CLOCKSOURCE_MASK(32),
148 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
149 };
150
openrisc_timer_init(void)151 static int __init openrisc_timer_init(void)
152 {
153 struct cpuinfo_or1k *cpuinfo = &cpuinfo_or1k[smp_processor_id()];
154
155 if (clocksource_register_hz(&openrisc_timer, cpuinfo->clock_frequency))
156 panic("failed to register clocksource");
157
158 /* Enable the incrementer: 'continuous' mode with interrupt disabled */
159 mtspr(SPR_TTMR, SPR_TTMR_CR);
160
161 return 0;
162 }
163
time_init(void)164 void __init time_init(void)
165 {
166 u32 upr;
167
168 upr = mfspr(SPR_UPR);
169 if (!(upr & SPR_UPR_TTP))
170 panic("Linux not supported on devices without tick timer");
171
172 openrisc_timer_init();
173 openrisc_clockevent_init();
174
175 of_clk_init(NULL);
176 timer_probe();
177 }
178