1 /**
2  * timer-ti-32k.c - OMAP2 32k Timer Support
3  *
4  * Copyright (C) 2009 Nokia Corporation
5  *
6  * Update to use new clocksource/clockevent layers
7  * Author: Kevin Hilman, MontaVista Software, Inc. <source@mvista.com>
8  * Copyright (C) 2007 MontaVista Software, Inc.
9  *
10  * Original driver:
11  * Copyright (C) 2005 Nokia Corporation
12  * Author: Paul Mundt <paul.mundt@nokia.com>
13  *         Juha Yrjölä <juha.yrjola@nokia.com>
14  * OMAP Dual-mode timer framework support by Timo Teras
15  *
16  * Some parts based off of TI's 24xx code:
17  *
18  * Copyright (C) 2004-2009 Texas Instruments, Inc.
19  *
20  * Roughly modelled after the OMAP1 MPU timer code.
21  * Added OMAP4 support - Santosh Shilimkar <santosh.shilimkar@ti.com>
22  *
23  * Copyright (C) 2015 Texas Instruments Incorporated - http://www.ti.com
24  *
25  * This program is free software: you can redistribute it and/or modify
26  * it under the terms of the GNU General Public License version 2  of
27  * the License as published by the Free Software Foundation.
28  *
29  * This program is distributed in the hope that it will be useful,
30  * but WITHOUT ANY WARRANTY; without even the implied warranty of
31  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
32  * GNU General Public License for more details.
33  *
34  * You should have received a copy of the GNU General Public License
35  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
36  */
37 
38 #include <linux/init.h>
39 #include <linux/time.h>
40 #include <linux/sched_clock.h>
41 #include <linux/clocksource.h>
42 #include <linux/of.h>
43 #include <linux/of_address.h>
44 
45 /*
46  * 32KHz clocksource ... always available, on pretty most chips except
47  * OMAP 730 and 1510.  Other timers could be used as clocksources, with
48  * higher resolution in free-running counter modes (e.g. 12 MHz xtal),
49  * but systems won't necessarily want to spend resources that way.
50  */
51 
52 #define OMAP2_32KSYNCNT_REV_OFF		0x0
53 #define OMAP2_32KSYNCNT_REV_SCHEME	(0x3 << 30)
54 #define OMAP2_32KSYNCNT_CR_OFF_LOW	0x10
55 #define OMAP2_32KSYNCNT_CR_OFF_HIGH	0x30
56 
57 struct ti_32k {
58 	void __iomem		*base;
59 	void __iomem		*counter;
60 	struct clocksource	cs;
61 };
62 
63 static inline struct ti_32k *to_ti_32k(struct clocksource *cs)
64 {
65 	return container_of(cs, struct ti_32k, cs);
66 }
67 
68 static cycle_t ti_32k_read_cycles(struct clocksource *cs)
69 {
70 	struct ti_32k *ti = to_ti_32k(cs);
71 
72 	return (cycle_t)readl_relaxed(ti->counter);
73 }
74 
75 static struct ti_32k ti_32k_timer = {
76 	.cs = {
77 		.name		= "32k_counter",
78 		.rating		= 250,
79 		.read		= ti_32k_read_cycles,
80 		.mask		= CLOCKSOURCE_MASK(32),
81 		.flags		= CLOCK_SOURCE_IS_CONTINUOUS |
82 				CLOCK_SOURCE_SUSPEND_NONSTOP,
83 	},
84 };
85 
86 static u64 notrace omap_32k_read_sched_clock(void)
87 {
88 	return ti_32k_read_cycles(&ti_32k_timer.cs);
89 }
90 
91 static int __init ti_32k_timer_init(struct device_node *np)
92 {
93 	int ret;
94 
95 	ti_32k_timer.base = of_iomap(np, 0);
96 	if (!ti_32k_timer.base) {
97 		pr_err("Can't ioremap 32k timer base\n");
98 		return -ENXIO;
99 	}
100 
101 	ti_32k_timer.counter = ti_32k_timer.base;
102 
103 	/*
104 	 * 32k sync Counter IP register offsets vary between the highlander
105 	 * version and the legacy ones.
106 	 *
107 	 * The 'SCHEME' bits(30-31) of the revision register is used to identify
108 	 * the version.
109 	 */
110 	if (readl_relaxed(ti_32k_timer.base + OMAP2_32KSYNCNT_REV_OFF) &
111 			OMAP2_32KSYNCNT_REV_SCHEME)
112 		ti_32k_timer.counter += OMAP2_32KSYNCNT_CR_OFF_HIGH;
113 	else
114 		ti_32k_timer.counter += OMAP2_32KSYNCNT_CR_OFF_LOW;
115 
116 	ret = clocksource_register_hz(&ti_32k_timer.cs, 32768);
117 	if (ret) {
118 		pr_err("32k_counter: can't register clocksource\n");
119 		return ret;
120 	}
121 
122 	sched_clock_register(omap_32k_read_sched_clock, 32, 32768);
123 	pr_info("OMAP clocksource: 32k_counter at 32768 Hz\n");
124 
125 	return 0;
126 }
127 CLOCKSOURCE_OF_DECLARE(ti_32k_timer, "ti,omap-counter32k",
128 		ti_32k_timer_init);
129