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/platform_device.h>
13 #include <linux/reset.h>
14 #include <linux/sched_clock.h>
15 #include <linux/slab.h>
16 
17 #include "timer-of.h"
18 
19 /*
20  * The OSTM contains independent channels.
21  * The first OSTM channel probed will be set up as a free running
22  * clocksource. Additionally we will use this clocksource for the system
23  * schedule timer sched_clock().
24  *
25  * The second (or more) channel probed will be set up as an interrupt
26  * driven clock event.
27  */
28 
29 static void __iomem *system_clock;	/* For sched_clock() */
30 
31 /* OSTM REGISTERS */
32 #define	OSTM_CMP		0x000	/* RW,32 */
33 #define	OSTM_CNT		0x004	/* R,32 */
34 #define	OSTM_TE			0x010	/* R,8 */
35 #define	OSTM_TS			0x014	/* W,8 */
36 #define	OSTM_TT			0x018	/* W,8 */
37 #define	OSTM_CTL		0x020	/* RW,8 */
38 
39 #define	TE			0x01
40 #define	TS			0x01
41 #define	TT			0x01
42 #define	CTL_PERIODIC		0x00
43 #define	CTL_ONESHOT		0x02
44 #define	CTL_FREERUN		0x02
45 
46 static void ostm_timer_stop(struct timer_of *to)
47 {
48 	if (readb(timer_of_base(to) + OSTM_TE) & TE) {
49 		writeb(TT, timer_of_base(to) + OSTM_TT);
50 
51 		/*
52 		 * Read back the register simply to confirm the write operation
53 		 * has completed since I/O writes can sometimes get queued by
54 		 * the bus architecture.
55 		 */
56 		while (readb(timer_of_base(to) + OSTM_TE) & TE)
57 			;
58 	}
59 }
60 
61 static int __init ostm_init_clksrc(struct timer_of *to)
62 {
63 	ostm_timer_stop(to);
64 
65 	writel(0, timer_of_base(to) + OSTM_CMP);
66 	writeb(CTL_FREERUN, timer_of_base(to) + OSTM_CTL);
67 	writeb(TS, timer_of_base(to) + OSTM_TS);
68 
69 	return clocksource_mmio_init(timer_of_base(to) + OSTM_CNT,
70 				     to->np->full_name, timer_of_rate(to), 300,
71 				     32, clocksource_mmio_readl_up);
72 }
73 
74 static u64 notrace ostm_read_sched_clock(void)
75 {
76 	return readl(system_clock);
77 }
78 
79 static void __init ostm_init_sched_clock(struct timer_of *to)
80 {
81 	system_clock = timer_of_base(to) + OSTM_CNT;
82 	sched_clock_register(ostm_read_sched_clock, 32, timer_of_rate(to));
83 }
84 
85 static int ostm_clock_event_next(unsigned long delta,
86 				 struct clock_event_device *ced)
87 {
88 	struct timer_of *to = to_timer_of(ced);
89 
90 	ostm_timer_stop(to);
91 
92 	writel(delta, timer_of_base(to) + OSTM_CMP);
93 	writeb(CTL_ONESHOT, timer_of_base(to) + OSTM_CTL);
94 	writeb(TS, timer_of_base(to) + OSTM_TS);
95 
96 	return 0;
97 }
98 
99 static int ostm_shutdown(struct clock_event_device *ced)
100 {
101 	struct timer_of *to = to_timer_of(ced);
102 
103 	ostm_timer_stop(to);
104 
105 	return 0;
106 }
107 static int ostm_set_periodic(struct clock_event_device *ced)
108 {
109 	struct timer_of *to = to_timer_of(ced);
110 
111 	if (clockevent_state_oneshot(ced) || clockevent_state_periodic(ced))
112 		ostm_timer_stop(to);
113 
114 	writel(timer_of_period(to) - 1, timer_of_base(to) + OSTM_CMP);
115 	writeb(CTL_PERIODIC, timer_of_base(to) + OSTM_CTL);
116 	writeb(TS, timer_of_base(to) + OSTM_TS);
117 
118 	return 0;
119 }
120 
121 static int ostm_set_oneshot(struct clock_event_device *ced)
122 {
123 	struct timer_of *to = to_timer_of(ced);
124 
125 	ostm_timer_stop(to);
126 
127 	return 0;
128 }
129 
130 static irqreturn_t ostm_timer_interrupt(int irq, void *dev_id)
131 {
132 	struct clock_event_device *ced = dev_id;
133 
134 	if (clockevent_state_oneshot(ced))
135 		ostm_timer_stop(to_timer_of(ced));
136 
137 	/* notify clockevent layer */
138 	if (ced->event_handler)
139 		ced->event_handler(ced);
140 
141 	return IRQ_HANDLED;
142 }
143 
144 static int __init ostm_init_clkevt(struct timer_of *to)
145 {
146 	struct clock_event_device *ced = &to->clkevt;
147 
148 	ced->features = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_PERIODIC;
149 	ced->set_state_shutdown = ostm_shutdown;
150 	ced->set_state_periodic = ostm_set_periodic;
151 	ced->set_state_oneshot = ostm_set_oneshot;
152 	ced->set_next_event = ostm_clock_event_next;
153 	ced->shift = 32;
154 	ced->rating = 300;
155 	ced->cpumask = cpumask_of(0);
156 	clockevents_config_and_register(ced, timer_of_rate(to), 0xf,
157 					0xffffffff);
158 
159 	return 0;
160 }
161 
162 static int __init ostm_init(struct device_node *np)
163 {
164 	struct reset_control *rstc;
165 	struct timer_of *to;
166 	int ret;
167 
168 	to = kzalloc(sizeof(*to), GFP_KERNEL);
169 	if (!to)
170 		return -ENOMEM;
171 
172 	rstc = of_reset_control_get_optional_exclusive(np, NULL);
173 	if (IS_ERR(rstc)) {
174 		ret = PTR_ERR(rstc);
175 		goto err_free;
176 	}
177 
178 	reset_control_deassert(rstc);
179 
180 	to->flags = TIMER_OF_BASE | TIMER_OF_CLOCK;
181 	if (system_clock) {
182 		/*
183 		 * clock sources don't use interrupts, clock events do
184 		 */
185 		to->flags |= TIMER_OF_IRQ;
186 		to->of_irq.flags = IRQF_TIMER | IRQF_IRQPOLL;
187 		to->of_irq.handler = ostm_timer_interrupt;
188 	}
189 
190 	ret = timer_of_init(np, to);
191 	if (ret)
192 		goto err_reset;
193 
194 	/*
195 	 * First probed device will be used as system clocksource. Any
196 	 * additional devices will be used as clock events.
197 	 */
198 	if (!system_clock) {
199 		ret = ostm_init_clksrc(to);
200 		if (ret)
201 			goto err_cleanup;
202 
203 		ostm_init_sched_clock(to);
204 		pr_info("%pOF: used for clocksource\n", np);
205 	} else {
206 		ret = ostm_init_clkevt(to);
207 		if (ret)
208 			goto err_cleanup;
209 
210 		pr_info("%pOF: used for clock events\n", np);
211 	}
212 
213 	return 0;
214 
215 err_cleanup:
216 	timer_of_cleanup(to);
217 err_reset:
218 	reset_control_assert(rstc);
219 	reset_control_put(rstc);
220 err_free:
221 	kfree(to);
222 	return ret;
223 }
224 
225 TIMER_OF_DECLARE(ostm, "renesas,ostm", ostm_init);
226 
227 #ifdef CONFIG_ARCH_RZG2L
228 static int __init ostm_probe(struct platform_device *pdev)
229 {
230 	struct device *dev = &pdev->dev;
231 
232 	return ostm_init(dev->of_node);
233 }
234 
235 static const struct of_device_id ostm_of_table[] = {
236 	{ .compatible = "renesas,ostm", },
237 	{ /* sentinel */ }
238 };
239 
240 static struct platform_driver ostm_device_driver = {
241 	.driver = {
242 		.name = "renesas_ostm",
243 		.of_match_table = of_match_ptr(ostm_of_table),
244 		.suppress_bind_attrs = true,
245 	},
246 };
247 builtin_platform_driver_probe(ostm_device_driver, ostm_probe);
248 #endif
249