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 irqreturn_t __irq_entry timer_interrupt(struct pt_regs *regs);
29
30 /* Test the timer ticks to count, used in sync routine */
31 inline void openrisc_timer_set(unsigned long count)
32 {
33 mtspr(SPR_TTCR, count);
34 }
35
36 /* Set the timer to trigger in delta cycles */
37 inline void openrisc_timer_set_next(unsigned long delta)
38 {
39 u32 c;
40
41 /* Read 32-bit counter value, add delta, mask off the low 28 bits.
42 * We're guaranteed delta won't be bigger than 28 bits because the
43 * generic timekeeping code ensures that for us.
44 */
45 c = mfspr(SPR_TTCR);
46 c += delta;
47 c &= SPR_TTMR_TP;
48
49 /* Set counter and enable interrupt.
50 * Keep timer in continuous mode always.
51 */
52 mtspr(SPR_TTMR, SPR_TTMR_CR | SPR_TTMR_IE | c);
53 }
54
55 static int openrisc_timer_set_next_event(unsigned long delta,
56 struct clock_event_device *dev)
57 {
58 openrisc_timer_set_next(delta);
59 return 0;
60 }
61
62 /* This is the clock event device based on the OR1K tick timer.
63 * As the timer is being used as a continuous clock-source (required for HR
64 * timers) we cannot enable the PERIODIC feature. The tick timer can run using
65 * one-shot events, so no problem.
66 */
67 static DEFINE_PER_CPU(struct clock_event_device, clockevent_openrisc_timer);
68
69 void openrisc_clockevent_init(void)
70 {
71 unsigned int cpu = smp_processor_id();
72 struct clock_event_device *evt =
73 &per_cpu(clockevent_openrisc_timer, cpu);
74 struct cpuinfo_or1k *cpuinfo = &cpuinfo_or1k[cpu];
75
76 mtspr(SPR_TTMR, SPR_TTMR_CR);
77
78 #ifdef CONFIG_SMP
79 evt->broadcast = tick_broadcast;
80 #endif
81 evt->name = "openrisc_timer_clockevent",
82 evt->features = CLOCK_EVT_FEAT_ONESHOT,
83 evt->rating = 300,
84 evt->set_next_event = openrisc_timer_set_next_event,
85
86 evt->cpumask = cpumask_of(cpu);
87
88 /* We only have 28 bits */
89 clockevents_config_and_register(evt, cpuinfo->clock_frequency,
90 100, 0x0fffffff);
91
92 }
93
94 static inline void timer_ack(void)
95 {
96 /* Clear the IP bit and disable further interrupts */
97 /* This can be done very simply... we just need to keep the timer
98 running, so just maintain the CR bits while clearing the rest
99 of the register
100 */
101 mtspr(SPR_TTMR, SPR_TTMR_CR);
102 }
103
104 /*
105 * The timer interrupt is mostly handled in generic code nowadays... this
106 * function just acknowledges the interrupt and fires the event handler that
107 * has been set on the clockevent device by the generic time management code.
108 *
109 * This function needs to be called by the timer exception handler and that's
110 * all the exception handler needs to do.
111 */
112
113 irqreturn_t __irq_entry timer_interrupt(struct pt_regs *regs)
114 {
115 struct pt_regs *old_regs = set_irq_regs(regs);
116 unsigned int cpu = smp_processor_id();
117 struct clock_event_device *evt =
118 &per_cpu(clockevent_openrisc_timer, cpu);
119
120 timer_ack();
121
122 /*
123 * update_process_times() expects us to have called irq_enter().
124 */
125 irq_enter();
126 evt->event_handler(evt);
127 irq_exit();
128
129 set_irq_regs(old_regs);
130
131 return IRQ_HANDLED;
132 }
133
134 /*
135 * Clocksource: Based on OpenRISC timer/counter
136 *
137 * This sets up the OpenRISC Tick Timer as a clock source. The tick timer
138 * is 32 bits wide and runs at the CPU clock frequency.
139 */
140 static u64 openrisc_timer_read(struct clocksource *cs)
141 {
142 return (u64) mfspr(SPR_TTCR);
143 }
144
145 static struct clocksource openrisc_timer = {
146 .name = "openrisc_timer",
147 .rating = 200,
148 .read = openrisc_timer_read,
149 .mask = CLOCKSOURCE_MASK(32),
150 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
151 };
152
153 static int __init openrisc_timer_init(void)
154 {
155 struct cpuinfo_or1k *cpuinfo = &cpuinfo_or1k[smp_processor_id()];
156
157 if (clocksource_register_hz(&openrisc_timer, cpuinfo->clock_frequency))
158 panic("failed to register clocksource");
159
160 /* Enable the incrementer: 'continuous' mode with interrupt disabled */
161 mtspr(SPR_TTMR, SPR_TTMR_CR);
162
163 return 0;
164 }
165
166 void __init time_init(void)
167 {
168 u32 upr;
169
170 upr = mfspr(SPR_UPR);
171 if (!(upr & SPR_UPR_TTP))
172 panic("Linux not supported on devices without tick timer");
173
174 openrisc_timer_init();
175 openrisc_clockevent_init();
176
177 of_clk_init(NULL);
178 timer_probe();
179 }
180
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