1/*
2 * linux/arch/arm/mach-omap1/timer32k.c
3 *
4 * OMAP 32K Timer
5 *
6 * Copyright (C) 2004 - 2005 Nokia Corporation
7 * Partial timer rewrite and additional dynamic tick timer support by
8 * Tony Lindgen <tony@atomide.com> and
9 * Tuukka Tikkanen <tuukka.tikkanen@elektrobit.com>
10 * OMAP Dual-mode timer framework support by Timo Teras
11 *
12 * MPU timer code based on the older MPU timer code for OMAP
13 * Copyright (C) 2000 RidgeRun, Inc.
14 * Author: Greg Lonnon <glonnon@ridgerun.com>
15 *
16 * This program is free software; you can redistribute it and/or modify it
17 * under the terms of the GNU General Public License as published by the
18 * Free Software Foundation; either version 2 of the License, or (at your
19 * option) any later version.
20 *
21 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
22 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
23 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN
24 * NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
25 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
26 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
27 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
28 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
30 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31 *
32 * You should have received a copy of the GNU General Public License along
33 * with this program; if not, write to the Free Software Foundation, Inc.,
34 * 675 Mass Ave, Cambridge, MA 02139, USA.
35 */
36
37#include <linux/kernel.h>
38#include <linux/init.h>
39#include <linux/delay.h>
40#include <linux/interrupt.h>
41#include <linux/sched.h>
42#include <linux/spinlock.h>
43#include <linux/err.h>
44#include <linux/clk.h>
45#include <linux/clocksource.h>
46#include <linux/clockchips.h>
47#include <linux/io.h>
48#include <linux/sched_clock.h>
49
50#include <asm/irq.h>
51#include <asm/mach/irq.h>
52#include <asm/mach/time.h>
53
54#include "hardware.h"
55#include "common.h"
56
57/*
58 * ---------------------------------------------------------------------------
59 * 32KHz OS timer
60 *
61 * This currently works only on 16xx, as 1510 does not have the continuous
62 * 32KHz synchronous timer. The 32KHz synchronous timer is used to keep track
63 * of time in addition to the 32KHz OS timer. Using only the 32KHz OS timer
64 * on 1510 would be possible, but the timer would not be as accurate as
65 * with the 32KHz synchronized timer.
66 * ---------------------------------------------------------------------------
67 */
68
69/* 16xx specific defines */
70#define OMAP1_32K_TIMER_BASE 0xfffb9000
71#define OMAP1_32KSYNC_TIMER_BASE 0xfffbc400
72#define OMAP1_32K_TIMER_CR 0x08
73#define OMAP1_32K_TIMER_TVR 0x00
74#define OMAP1_32K_TIMER_TCR 0x04
75
76#define OMAP_32K_TICKS_PER_SEC (32768)
77
78/*
79 * TRM says 1 / HZ = ( TVR + 1) / 32768, so TRV = (32768 / HZ) - 1
80 * so with HZ = 128, TVR = 255.
81 */
82#define OMAP_32K_TIMER_TICK_PERIOD ((OMAP_32K_TICKS_PER_SEC / HZ) - 1)
83
84#define JIFFIES_TO_HW_TICKS(nr_jiffies, clock_rate) \
85 (((nr_jiffies) * (clock_rate)) / HZ)
86
87static inline void omap_32k_timer_write(int val, int reg)
88{
89 omap_writew(v: val, OMAP1_32K_TIMER_BASE + reg);
90}
91
92static inline void omap_32k_timer_start(unsigned long load_val)
93{
94 if (!load_val)
95 load_val = 1;
96 omap_32k_timer_write(val: load_val, OMAP1_32K_TIMER_TVR);
97 omap_32k_timer_write(val: 0x0f, OMAP1_32K_TIMER_CR);
98}
99
100static inline void omap_32k_timer_stop(void)
101{
102 omap_32k_timer_write(val: 0x0, OMAP1_32K_TIMER_CR);
103}
104
105#define omap_32k_timer_ack_irq()
106
107static int omap_32k_timer_set_next_event(unsigned long delta,
108 struct clock_event_device *dev)
109{
110 omap_32k_timer_start(load_val: delta);
111
112 return 0;
113}
114
115static int omap_32k_timer_shutdown(struct clock_event_device *evt)
116{
117 omap_32k_timer_stop();
118 return 0;
119}
120
121static int omap_32k_timer_set_periodic(struct clock_event_device *evt)
122{
123 omap_32k_timer_stop();
124 omap_32k_timer_start(OMAP_32K_TIMER_TICK_PERIOD);
125 return 0;
126}
127
128static struct clock_event_device clockevent_32k_timer = {
129 .name = "32k-timer",
130 .features = CLOCK_EVT_FEAT_PERIODIC |
131 CLOCK_EVT_FEAT_ONESHOT,
132 .set_next_event = omap_32k_timer_set_next_event,
133 .set_state_shutdown = omap_32k_timer_shutdown,
134 .set_state_periodic = omap_32k_timer_set_periodic,
135 .set_state_oneshot = omap_32k_timer_shutdown,
136 .tick_resume = omap_32k_timer_shutdown,
137};
138
139static irqreturn_t omap_32k_timer_interrupt(int irq, void *dev_id)
140{
141 struct clock_event_device *evt = &clockevent_32k_timer;
142 omap_32k_timer_ack_irq();
143
144 evt->event_handler(evt);
145
146 return IRQ_HANDLED;
147}
148
149static __init void omap_init_32k_timer(void)
150{
151 if (request_irq(INT_OS_TIMER, handler: omap_32k_timer_interrupt,
152 IRQF_TIMER | IRQF_IRQPOLL, name: "32KHz timer", NULL))
153 pr_err("Failed to request irq %d(32KHz timer)\n", INT_OS_TIMER);
154
155 clockevent_32k_timer.cpumask = cpumask_of(0);
156 clockevents_config_and_register(dev: &clockevent_32k_timer,
157 OMAP_32K_TICKS_PER_SEC, min_delta: 1, max_delta: 0xfffffffe);
158}
159
160/* OMAP2_32KSYNCNT_CR_OFF: offset of 32ksync counter register */
161#define OMAP2_32KSYNCNT_REV_OFF 0x0
162#define OMAP2_32KSYNCNT_REV_SCHEME (0x3 << 30)
163#define OMAP2_32KSYNCNT_CR_OFF_LOW 0x10
164#define OMAP2_32KSYNCNT_CR_OFF_HIGH 0x30
165
166/*
167 * 32KHz clocksource ... always available, on pretty most chips except
168 * OMAP 730 and 1510. Other timers could be used as clocksources, with
169 * higher resolution in free-running counter modes (e.g. 12 MHz xtal),
170 * but systems won't necessarily want to spend resources that way.
171 */
172static void __iomem *sync32k_cnt_reg;
173
174static u64 notrace omap_32k_read_sched_clock(void)
175{
176 return sync32k_cnt_reg ? readl_relaxed(sync32k_cnt_reg) : 0;
177}
178
179static struct timespec64 persistent_ts;
180static cycles_t cycles;
181static unsigned int persistent_mult, persistent_shift;
182
183/**
184 * omap_read_persistent_clock64 - Return time from a persistent clock.
185 * @ts: &struct timespec64 for the returned time
186 *
187 * Reads the time from a source which isn't disabled during PM, the
188 * 32k sync timer. Convert the cycles elapsed since last read into
189 * nsecs and adds to a monotonically increasing timespec64.
190 */
191static void omap_read_persistent_clock64(struct timespec64 *ts)
192{
193 unsigned long long nsecs;
194 cycles_t last_cycles;
195
196 last_cycles = cycles;
197 cycles = sync32k_cnt_reg ? readl_relaxed(sync32k_cnt_reg) : 0;
198
199 nsecs = clocksource_cyc2ns(cycles: cycles - last_cycles,
200 mult: persistent_mult, shift: persistent_shift);
201
202 timespec64_add_ns(a: &persistent_ts, ns: nsecs);
203
204 *ts = persistent_ts;
205}
206
207/**
208 * omap_init_clocksource_32k - setup and register counter 32k as a
209 * kernel clocksource
210 * @vbase: base addr of counter_32k module
211 *
212 * Returns: %0 upon success or negative error code upon failure.
213 *
214 */
215static int __init omap_init_clocksource_32k(void __iomem *vbase)
216{
217 int ret;
218
219 /*
220 * 32k sync Counter IP register offsets vary between the
221 * highlander version and the legacy ones.
222 * The 'SCHEME' bits(30-31) of the revision register is used
223 * to identify the version.
224 */
225 if (readl_relaxed(vbase + OMAP2_32KSYNCNT_REV_OFF) &
226 OMAP2_32KSYNCNT_REV_SCHEME)
227 sync32k_cnt_reg = vbase + OMAP2_32KSYNCNT_CR_OFF_HIGH;
228 else
229 sync32k_cnt_reg = vbase + OMAP2_32KSYNCNT_CR_OFF_LOW;
230
231 /*
232 * 120000 rough estimate from the calculations in
233 * __clocksource_update_freq_scale.
234 */
235 clocks_calc_mult_shift(mult: &persistent_mult, shift: &persistent_shift,
236 from: 32768, NSEC_PER_SEC, minsec: 120000);
237
238 ret = clocksource_mmio_init(sync32k_cnt_reg, "32k_counter", 32768,
239 250, 32, clocksource_mmio_readl_up);
240 if (ret) {
241 pr_err("32k_counter: can't register clocksource\n");
242 return ret;
243 }
244
245 sched_clock_register(read: omap_32k_read_sched_clock, bits: 32, rate: 32768);
246 register_persistent_clock(omap_read_persistent_clock64);
247 pr_info("OMAP clocksource: 32k_counter at 32768 Hz\n");
248
249 return 0;
250}
251
252/*
253 * ---------------------------------------------------------------------------
254 * Timer initialization
255 * ---------------------------------------------------------------------------
256 */
257int __init omap_32k_timer_init(void)
258{
259 int ret = -ENODEV;
260
261 if (cpu_is_omap16xx()) {
262 void __iomem *base;
263 struct clk *sync32k_ick;
264
265 base = ioremap(OMAP1_32KSYNC_TIMER_BASE, SZ_1K);
266 if (!base) {
267 pr_err("32k_counter: failed to map base addr\n");
268 return -ENODEV;
269 }
270
271 sync32k_ick = clk_get(NULL, id: "omap_32ksync_ick");
272 if (!IS_ERR(ptr: sync32k_ick))
273 clk_prepare_enable(clk: sync32k_ick);
274
275 ret = omap_init_clocksource_32k(vbase: base);
276 }
277
278 if (!ret)
279 omap_init_32k_timer();
280
281 return ret;
282}
283

source code of linux/arch/arm/mach-omap1/timer32k.c