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
29static 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
46static 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
61static 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
74static u64 notrace ostm_read_sched_clock(void)
75{
76	return readl(system_clock);
77}
78
79static 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
85static 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
99static 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}
107static 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
121static 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
130static 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
144static 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
162static 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
215err_cleanup:
216	timer_of_cleanup(to);
217err_reset:
218	reset_control_assert(rstc);
219	reset_control_put(rstc);
220err_free:
221	kfree(to);
222	return ret;
223}
224
225TIMER_OF_DECLARE(ostm, "renesas,ostm", ostm_init);
226
227#ifdef CONFIG_ARCH_RZG2L
228static 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
235static const struct of_device_id ostm_of_table[] = {
236	{ .compatible = "renesas,ostm", },
237	{ /* sentinel */ }
238};
239
240static 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};
247builtin_platform_driver_probe(ostm_device_driver, ostm_probe);
248#endif
249