dw_apb_timer_of.c revision 326e31eebe61dc838e031ea16968b2cfb43443e3 
1/*
2 * Copyright (C) 2012 Altera Corporation
3 * Copyright (c) 2011 Picochip Ltd., Jamie Iles
4 *
5 * Modified from mach-picoxcell/time.c
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14 * GNU General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
18 */
19#include <linux/dw_apb_timer.h>
20#include <linux/of.h>
21#include <linux/of_address.h>
22#include <linux/of_irq.h>
23#include <linux/clk.h>
24#include <linux/sched_clock.h>
25
26static void timer_get_base_and_rate(struct device_node *np,
27				    void __iomem **base, u32 *rate)
28{
29	struct clk *timer_clk;
30	struct clk *pclk;
31
32	*base = of_iomap(np, 0);
33
34	if (!*base)
35		panic("Unable to map regs for %s", np->name);
36
37	/*
38	 * Not all implementations use a periphal clock, so don't panic
39	 * if it's not present
40	 */
41	pclk = of_clk_get_by_name(np, "pclk");
42	if (!IS_ERR(pclk))
43		if (clk_prepare_enable(pclk))
44			pr_warn("pclk for %s is present, but could not be activated\n",
45				np->name);
46
47	timer_clk = of_clk_get_by_name(np, "timer");
48	if (IS_ERR(timer_clk))
49		goto try_clock_freq;
50
51	if (!clk_prepare_enable(timer_clk)) {
52		*rate = clk_get_rate(timer_clk);
53		return;
54	}
55
56try_clock_freq:
57	if (of_property_read_u32(np, "clock-freq", rate) &&
58		of_property_read_u32(np, "clock-frequency", rate))
59		panic("No clock nor clock-frequency property for %s", np->name);
60}
61
62static void add_clockevent(struct device_node *event_timer)
63{
64	void __iomem *iobase;
65	struct dw_apb_clock_event_device *ced;
66	u32 irq, rate;
67
68	irq = irq_of_parse_and_map(event_timer, 0);
69	if (irq == 0)
70		panic("No IRQ for clock event timer");
71
72	timer_get_base_and_rate(event_timer, &iobase, &rate);
73
74	ced = dw_apb_clockevent_init(0, event_timer->name, 300, iobase, irq,
75				     rate);
76	if (!ced)
77		panic("Unable to initialise clockevent device");
78
79	dw_apb_clockevent_register(ced);
80}
81
82static void __iomem *sched_io_base;
83static u32 sched_rate;
84
85static void add_clocksource(struct device_node *source_timer)
86{
87	void __iomem *iobase;
88	struct dw_apb_clocksource *cs;
89	u32 rate;
90
91	timer_get_base_and_rate(source_timer, &iobase, &rate);
92
93	cs = dw_apb_clocksource_init(300, source_timer->name, iobase, rate);
94	if (!cs)
95		panic("Unable to initialise clocksource device");
96
97	dw_apb_clocksource_start(cs);
98	dw_apb_clocksource_register(cs);
99
100	/*
101	 * Fallback to use the clocksource as sched_clock if no separate
102	 * timer is found. sched_io_base then points to the current_value
103	 * register of the clocksource timer.
104	 */
105	sched_io_base = iobase + 0x04;
106	sched_rate = rate;
107}
108
109static u64 read_sched_clock(void)
110{
111	return __raw_readl(sched_io_base);
112}
113
114static const struct of_device_id sptimer_ids[] __initconst = {
115	{ .compatible = "picochip,pc3x2-rtc" },
116	{ .compatible = "snps,dw-apb-timer-sp" },
117	{ /* Sentinel */ },
118};
119
120static void init_sched_clock(void)
121{
122	struct device_node *sched_timer;
123
124	sched_timer = of_find_matching_node(NULL, sptimer_ids);
125	if (sched_timer) {
126		timer_get_base_and_rate(sched_timer, &sched_io_base,
127					&sched_rate);
128		of_node_put(sched_timer);
129	}
130
131	sched_clock_register(read_sched_clock, 32, sched_rate);
132}
133
134static int num_called;
135static void __init dw_apb_timer_init(struct device_node *timer)
136{
137	switch (num_called) {
138	case 0:
139		pr_debug("%s: found clockevent timer\n", __func__);
140		add_clockevent(timer);
141		break;
142	case 1:
143		pr_debug("%s: found clocksource timer\n", __func__);
144		add_clocksource(timer);
145		init_sched_clock();
146		break;
147	default:
148		break;
149	}
150
151	num_called++;
152}
153CLOCKSOURCE_OF_DECLARE(pc3x2_timer, "picochip,pc3x2-timer", dw_apb_timer_init);
154CLOCKSOURCE_OF_DECLARE(apb_timer, "snps,dw-apb-timer-osc", dw_apb_timer_init);
155