1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Renesas Timer Support - OSTM
4 *
5 * Copyright (C) 2017 Renesas Electronics America, Inc.
6 * Copyright (C) 2017 Chris Brandt
7 */
8
9 #include <linux/clk.h>
10 #include <linux/clockchips.h>
11 #include <linux/interrupt.h>
12 #include <linux/sched_clock.h>
13 #include <linux/slab.h>
14
15 #include "timer-of.h"
16
17 /*
18 * The OSTM contains independent channels.
19 * The first OSTM channel probed will be set up as a free running
20 * clocksource. Additionally we will use this clocksource for the system
21 * schedule timer sched_clock().
22 *
23 * The second (or more) channel probed will be set up as an interrupt
24 * driven clock event.
25 */
26
27 static void __iomem *system_clock; /* For sched_clock() */
28
29 /* OSTM REGISTERS */
30 #define OSTM_CMP 0x000 /* RW,32 */
31 #define OSTM_CNT 0x004 /* R,32 */
32 #define OSTM_TE 0x010 /* R,8 */
33 #define OSTM_TS 0x014 /* W,8 */
34 #define OSTM_TT 0x018 /* W,8 */
35 #define OSTM_CTL 0x020 /* RW,8 */
36
37 #define TE 0x01
38 #define TS 0x01
39 #define TT 0x01
40 #define CTL_PERIODIC 0x00
41 #define CTL_ONESHOT 0x02
42 #define CTL_FREERUN 0x02
43
ostm_timer_stop(struct timer_of * to)44 static void ostm_timer_stop(struct timer_of *to)
45 {
46 if (readb(timer_of_base(to) + OSTM_TE) & TE) {
47 writeb(TT, timer_of_base(to) + OSTM_TT);
48
49 /*
50 * Read back the register simply to confirm the write operation
51 * has completed since I/O writes can sometimes get queued by
52 * the bus architecture.
53 */
54 while (readb(timer_of_base(to) + OSTM_TE) & TE)
55 ;
56 }
57 }
58
ostm_init_clksrc(struct timer_of * to)59 static int __init ostm_init_clksrc(struct timer_of *to)
60 {
61 ostm_timer_stop(to);
62
63 writel(0, timer_of_base(to) + OSTM_CMP);
64 writeb(CTL_FREERUN, timer_of_base(to) + OSTM_CTL);
65 writeb(TS, timer_of_base(to) + OSTM_TS);
66
67 return clocksource_mmio_init(timer_of_base(to) + OSTM_CNT,
68 to->np->full_name, timer_of_rate(to), 300,
69 32, clocksource_mmio_readl_up);
70 }
71
ostm_read_sched_clock(void)72 static u64 notrace ostm_read_sched_clock(void)
73 {
74 return readl(system_clock);
75 }
76
ostm_init_sched_clock(struct timer_of * to)77 static void __init ostm_init_sched_clock(struct timer_of *to)
78 {
79 system_clock = timer_of_base(to) + OSTM_CNT;
80 sched_clock_register(ostm_read_sched_clock, 32, timer_of_rate(to));
81 }
82
ostm_clock_event_next(unsigned long delta,struct clock_event_device * ced)83 static int ostm_clock_event_next(unsigned long delta,
84 struct clock_event_device *ced)
85 {
86 struct timer_of *to = to_timer_of(ced);
87
88 ostm_timer_stop(to);
89
90 writel(delta, timer_of_base(to) + OSTM_CMP);
91 writeb(CTL_ONESHOT, timer_of_base(to) + OSTM_CTL);
92 writeb(TS, timer_of_base(to) + OSTM_TS);
93
94 return 0;
95 }
96
ostm_shutdown(struct clock_event_device * ced)97 static int ostm_shutdown(struct clock_event_device *ced)
98 {
99 struct timer_of *to = to_timer_of(ced);
100
101 ostm_timer_stop(to);
102
103 return 0;
104 }
ostm_set_periodic(struct clock_event_device * ced)105 static int ostm_set_periodic(struct clock_event_device *ced)
106 {
107 struct timer_of *to = to_timer_of(ced);
108
109 if (clockevent_state_oneshot(ced) || clockevent_state_periodic(ced))
110 ostm_timer_stop(to);
111
112 writel(timer_of_period(to) - 1, timer_of_base(to) + OSTM_CMP);
113 writeb(CTL_PERIODIC, timer_of_base(to) + OSTM_CTL);
114 writeb(TS, timer_of_base(to) + OSTM_TS);
115
116 return 0;
117 }
118
ostm_set_oneshot(struct clock_event_device * ced)119 static int ostm_set_oneshot(struct clock_event_device *ced)
120 {
121 struct timer_of *to = to_timer_of(ced);
122
123 ostm_timer_stop(to);
124
125 return 0;
126 }
127
ostm_timer_interrupt(int irq,void * dev_id)128 static irqreturn_t ostm_timer_interrupt(int irq, void *dev_id)
129 {
130 struct clock_event_device *ced = dev_id;
131
132 if (clockevent_state_oneshot(ced))
133 ostm_timer_stop(to_timer_of(ced));
134
135 /* notify clockevent layer */
136 if (ced->event_handler)
137 ced->event_handler(ced);
138
139 return IRQ_HANDLED;
140 }
141
ostm_init_clkevt(struct timer_of * to)142 static int __init ostm_init_clkevt(struct timer_of *to)
143 {
144 struct clock_event_device *ced = &to->clkevt;
145
146 ced->features = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_PERIODIC;
147 ced->set_state_shutdown = ostm_shutdown;
148 ced->set_state_periodic = ostm_set_periodic;
149 ced->set_state_oneshot = ostm_set_oneshot;
150 ced->set_next_event = ostm_clock_event_next;
151 ced->shift = 32;
152 ced->rating = 300;
153 ced->cpumask = cpumask_of(0);
154 clockevents_config_and_register(ced, timer_of_rate(to), 0xf,
155 0xffffffff);
156
157 return 0;
158 }
159
ostm_init(struct device_node * np)160 static int __init ostm_init(struct device_node *np)
161 {
162 struct timer_of *to;
163 int ret;
164
165 to = kzalloc(sizeof(*to), GFP_KERNEL);
166 if (!to)
167 return -ENOMEM;
168
169 to->flags = TIMER_OF_BASE | TIMER_OF_CLOCK;
170 if (system_clock) {
171 /*
172 * clock sources don't use interrupts, clock events do
173 */
174 to->flags |= TIMER_OF_IRQ;
175 to->of_irq.flags = IRQF_TIMER | IRQF_IRQPOLL;
176 to->of_irq.handler = ostm_timer_interrupt;
177 }
178
179 ret = timer_of_init(np, to);
180 if (ret)
181 goto err_free;
182
183 /*
184 * First probed device will be used as system clocksource. Any
185 * additional devices will be used as clock events.
186 */
187 if (!system_clock) {
188 ret = ostm_init_clksrc(to);
189 if (ret)
190 goto err_cleanup;
191
192 ostm_init_sched_clock(to);
193 pr_info("%pOF: used for clocksource\n", np);
194 } else {
195 ret = ostm_init_clkevt(to);
196 if (ret)
197 goto err_cleanup;
198
199 pr_info("%pOF: used for clock events\n", np);
200 }
201
202 return 0;
203
204 err_cleanup:
205 timer_of_cleanup(to);
206 err_free:
207 kfree(to);
208 return ret;
209 }
210
211 TIMER_OF_DECLARE(ostm, "renesas,ostm", ostm_init);
212