1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Cirrus Logic EP93xx timer driver.
4 * Copyright (C) 2021 Nikita Shubin <nikita.shubin@maquefel.me>
5 *
6 * Based on a rewrite of arch/arm/mach-ep93xx/timer.c:
7 */
8
9#include <linux/clockchips.h>
10#include <linux/clocksource.h>
11#include <linux/init.h>
12#include <linux/interrupt.h>
13#include <linux/io.h>
14#include <linux/io-64-nonatomic-lo-hi.h>
15#include <linux/irq.h>
16#include <linux/kernel.h>
17#include <linux/of_address.h>
18#include <linux/of_irq.h>
19#include <linux/sched_clock.h>
20
21#include <asm/mach/time.h>
22
23/*************************************************************************
24 * Timer handling for EP93xx
25 *************************************************************************
26 * The ep93xx has four internal timers.  Timers 1, 2 (both 16 bit) and
27 * 3 (32 bit) count down at 508 kHz, are self-reloading, and can generate
28 * an interrupt on underflow.  Timer 4 (40 bit) counts down at 983.04 kHz,
29 * is free-running, and can't generate interrupts.
30 *
31 * The 508 kHz timers are ideal for use for the timer interrupt, as the
32 * most common values of HZ divide 508 kHz nicely.  We pick the 32 bit
33 * timer (timer 3) to get as long sleep intervals as possible when using
34 * CONFIG_NO_HZ.
35 *
36 * The higher clock rate of timer 4 makes it a better choice than the
37 * other timers for use as clock source and for sched_clock(), providing
38 * a stable 40 bit time base.
39 *************************************************************************
40 */
41
42#define EP93XX_TIMER1_LOAD		0x00
43#define EP93XX_TIMER1_VALUE		0x04
44#define EP93XX_TIMER1_CONTROL		0x08
45#define EP93XX_TIMER123_CONTROL_ENABLE	BIT(7)
46#define EP93XX_TIMER123_CONTROL_MODE	BIT(6)
47#define EP93XX_TIMER123_CONTROL_CLKSEL	BIT(3)
48#define EP93XX_TIMER1_CLEAR		0x0c
49#define EP93XX_TIMER2_LOAD		0x20
50#define EP93XX_TIMER2_VALUE		0x24
51#define EP93XX_TIMER2_CONTROL		0x28
52#define EP93XX_TIMER2_CLEAR		0x2c
53/*
54 * This read-only register contains the low word of the time stamp debug timer
55 * ( Timer4). When this register is read, the high byte of the Timer4 counter is
56 * saved in the Timer4ValueHigh register.
57 */
58#define EP93XX_TIMER4_VALUE_LOW		0x60
59#define EP93XX_TIMER4_VALUE_HIGH	0x64
60#define EP93XX_TIMER4_VALUE_HIGH_ENABLE	BIT(8)
61#define EP93XX_TIMER3_LOAD		0x80
62#define EP93XX_TIMER3_VALUE		0x84
63#define EP93XX_TIMER3_CONTROL		0x88
64#define EP93XX_TIMER3_CLEAR		0x8c
65
66#define EP93XX_TIMER123_RATE		508469
67#define EP93XX_TIMER4_RATE		983040
68
69struct ep93xx_tcu {
70	void __iomem *base;
71};
72
73static struct ep93xx_tcu *ep93xx_tcu;
74
75static u64 ep93xx_clocksource_read(struct clocksource *c)
76{
77	struct ep93xx_tcu *tcu = ep93xx_tcu;
78
79	return lo_hi_readq(tcu->base + EP93XX_TIMER4_VALUE_LOW) & GENMASK_ULL(39, 0);
80}
81
82static u64 notrace ep93xx_read_sched_clock(void)
83{
84	return ep93xx_clocksource_read(NULL);
85}
86
87static int ep93xx_clkevt_set_next_event(unsigned long next,
88					struct clock_event_device *evt)
89{
90	struct ep93xx_tcu *tcu = ep93xx_tcu;
91	/* Default mode: periodic, off, 508 kHz */
92	u32 tmode = EP93XX_TIMER123_CONTROL_MODE |
93	EP93XX_TIMER123_CONTROL_CLKSEL;
94
95	/* Clear timer */
96	writel(tmode, tcu->base + EP93XX_TIMER3_CONTROL);
97
98	/* Set next event */
99	writel(next, tcu->base + EP93XX_TIMER3_LOAD);
100	writel(tmode | EP93XX_TIMER123_CONTROL_ENABLE,
101	       tcu->base + EP93XX_TIMER3_CONTROL);
102	return 0;
103}
104
105static int ep93xx_clkevt_shutdown(struct clock_event_device *evt)
106{
107	struct ep93xx_tcu *tcu = ep93xx_tcu;
108	/* Disable timer */
109	writel(0, tcu->base + EP93XX_TIMER3_CONTROL);
110
111	return 0;
112}
113
114static struct clock_event_device ep93xx_clockevent = {
115	.name			= "timer1",
116	.features		= CLOCK_EVT_FEAT_ONESHOT,
117	.set_state_shutdown	= ep93xx_clkevt_shutdown,
118	.set_state_oneshot	= ep93xx_clkevt_shutdown,
119	.tick_resume		= ep93xx_clkevt_shutdown,
120	.set_next_event		= ep93xx_clkevt_set_next_event,
121	.rating			= 300,
122};
123
124static irqreturn_t ep93xx_timer_interrupt(int irq, void *dev_id)
125{
126	struct ep93xx_tcu *tcu = ep93xx_tcu;
127	struct clock_event_device *evt = dev_id;
128
129	/* Writing any value clears the timer interrupt */
130	writel(1, tcu->base + EP93XX_TIMER3_CLEAR);
131
132	evt->event_handler(evt);
133
134	return IRQ_HANDLED;
135}
136
137static int __init ep93xx_timer_of_init(struct device_node *np)
138{
139	int irq;
140	unsigned long flags = IRQF_TIMER | IRQF_IRQPOLL;
141	struct ep93xx_tcu *tcu;
142	int ret;
143
144	tcu = kzalloc(sizeof(*tcu), GFP_KERNEL);
145	if (!tcu)
146		return -ENOMEM;
147
148	tcu->base = of_iomap(np, 0);
149	if (!tcu->base) {
150		pr_err("Can't remap registers\n");
151		ret = -ENXIO;
152		goto out_free;
153	}
154
155	ep93xx_tcu = tcu;
156
157	irq = irq_of_parse_and_map(np, 0);
158	if (!irq) {
159		ret = -EINVAL;
160		pr_err("EP93XX Timer Can't parse IRQ %d", irq);
161		goto out_free;
162	}
163
164	/* Enable and register clocksource and sched_clock on timer 4 */
165	writel(EP93XX_TIMER4_VALUE_HIGH_ENABLE,
166	       tcu->base + EP93XX_TIMER4_VALUE_HIGH);
167	clocksource_mmio_init(NULL, "timer4",
168				EP93XX_TIMER4_RATE, 200, 40,
169				ep93xx_clocksource_read);
170	sched_clock_register(ep93xx_read_sched_clock, 40,
171			     EP93XX_TIMER4_RATE);
172
173	/* Set up clockevent on timer 3 */
174	if (request_irq(irq, ep93xx_timer_interrupt, flags, "ep93xx timer",
175		&ep93xx_clockevent))
176		pr_err("Failed to request irq %d (ep93xx timer)\n", irq);
177
178	clockevents_config_and_register(&ep93xx_clockevent,
179				EP93XX_TIMER123_RATE,
180				1,
181				UINT_MAX);
182
183	return 0;
184
185out_free:
186	kfree(tcu);
187	return ret;
188}
189TIMER_OF_DECLARE(ep93xx_timer, "cirrus,ep9301-timer", ep93xx_timer_of_init);
190