1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
|
/*
* Clock event driver for the CS5535/CS5536
*
* Copyright (C) 2006, Advanced Micro Devices, Inc.
* Copyright (C) 2007 Andres Salomon <dilinger@debian.org>
* Copyright (C) 2009 Andres Salomon <dilinger@collabora.co.uk>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of version 2 of the GNU General Public License
* as published by the Free Software Foundation.
*
* The MFGPTs are documented in AMD Geode CS5536 Companion Device Data Book.
*/
#include <linux/kernel.h>
#include <linux/irq.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/cs5535.h>
#include <linux/clockchips.h>
#define DRV_NAME "cs5535-clockevt"
static int timer_irq;
module_param_named(irq, timer_irq, int, 0644);
MODULE_PARM_DESC(irq, "Which IRQ to use for the clock source MFGPT ticks.");
/*
* We are using the 32.768kHz input clock - it's the only one that has the
* ranges we find desirable. The following table lists the suitable
* divisors and the associated Hz, minimum interval and the maximum interval:
*
* Divisor Hz Min Delta (s) Max Delta (s)
* 1 32768 .00048828125 2.000
* 2 16384 .0009765625 4.000
* 4 8192 .001953125 8.000
* 8 4096 .00390625 16.000
* 16 2048 .0078125 32.000
* 32 1024 .015625 64.000
* 64 512 .03125 128.000
* 128 256 .0625 256.000
* 256 128 .125 512.000
*/
static unsigned int cs5535_tick_mode = CLOCK_EVT_MODE_SHUTDOWN;
static struct cs5535_mfgpt_timer *cs5535_event_clock;
/* Selected from the table above */
#define MFGPT_DIVISOR 16
#define MFGPT_SCALE 4 /* divisor = 2^(scale) */
#define MFGPT_HZ (32768 / MFGPT_DIVISOR)
#define MFGPT_PERIODIC (MFGPT_HZ / HZ)
/*
* The MFPGT timers on the CS5536 provide us with suitable timers to use
* as clock event sources - not as good as a HPET or APIC, but certainly
* better than the PIT. This isn't a general purpose MFGPT driver, but
* a simplified one designed specifically to act as a clock event source.
* For full details about the MFGPT, please consult the CS5536 data sheet.
*/
static void disable_timer(struct cs5535_mfgpt_timer *timer)
{
/* avoid races by clearing CMP1 and CMP2 unconditionally */
cs5535_mfgpt_write(timer, MFGPT_REG_SETUP,
(uint16_t) ~MFGPT_SETUP_CNTEN | MFGPT_SETUP_CMP1 |
MFGPT_SETUP_CMP2);
}
static void start_timer(struct cs5535_mfgpt_timer *timer, uint16_t delta)
{
cs5535_mfgpt_write(timer, MFGPT_REG_CMP2, delta);
cs5535_mfgpt_write(timer, MFGPT_REG_COUNTER, 0);
cs5535_mfgpt_write(timer, MFGPT_REG_SETUP,
MFGPT_SETUP_CNTEN | MFGPT_SETUP_CMP2);
}
static void mfgpt_set_mode(enum clock_event_mode mode,
struct clock_event_device *evt)
{
disable_timer(cs5535_event_clock);
if (mode == CLOCK_EVT_MODE_PERIODIC)
start_timer(cs5535_event_clock, MFGPT_PERIODIC);
cs5535_tick_mode = mode;
}
static int mfgpt_next_event(unsigned long delta, struct clock_event_device *evt)
{
start_timer(cs5535_event_clock, delta);
return 0;
}
static struct clock_event_device cs5535_clockevent = {
.name = DRV_NAME,
.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
.set_mode = mfgpt_set_mode,
.set_next_event = mfgpt_next_event,
.rating = 250,
.shift = 32
};
static irqreturn_t mfgpt_tick(int irq, void *dev_id)
{
uint16_t val = cs5535_mfgpt_read(cs5535_event_clock, MFGPT_REG_SETUP);
/* See if the interrupt was for us */
if (!(val & (MFGPT_SETUP_SETUP | MFGPT_SETUP_CMP2 | MFGPT_SETUP_CMP1)))
return IRQ_NONE;
/* Turn off the clock (and clear the event) */
disable_timer(cs5535_event_clock);
if (cs5535_tick_mode == CLOCK_EVT_MODE_SHUTDOWN)
return IRQ_HANDLED;
/* Clear the counter */
cs5535_mfgpt_write(cs5535_event_clock, MFGPT_REG_COUNTER, 0);
/* Restart the clock in periodic mode */
if (cs5535_tick_mode == CLOCK_EVT_MODE_PERIODIC)
cs5535_mfgpt_write(cs5535_event_clock, MFGPT_REG_SETUP,
MFGPT_SETUP_CNTEN | MFGPT_SETUP_CMP2);
cs5535_clockevent.event_handler(&cs5535_clockevent);
return IRQ_HANDLED;
}
static struct irqaction mfgptirq = {
.handler = mfgpt_tick,
.flags = IRQF_DISABLED | IRQF_NOBALANCING | IRQF_TIMER,
.name = DRV_NAME,
};
static int __init cs5535_mfgpt_init(void)
{
struct cs5535_mfgpt_timer *timer;
int ret;
uint16_t val;
timer = cs5535_mfgpt_alloc_timer(MFGPT_TIMER_ANY, MFGPT_DOMAIN_WORKING);
if (!timer) {
printk(KERN_ERR DRV_NAME ": Could not allocate MFPGT timer\n");
return -ENODEV;
}
cs5535_event_clock = timer;
/* Set up the IRQ on the MFGPT side */
if (cs5535_mfgpt_setup_irq(timer, MFGPT_CMP2, &timer_irq)) {
printk(KERN_ERR DRV_NAME ": Could not set up IRQ %d\n",
timer_irq);
goto err_timer;
}
/* And register it with the kernel */
ret = setup_irq(timer_irq, &mfgptirq);
if (ret) {
printk(KERN_ERR DRV_NAME ": Unable to set up the interrupt.\n");
goto err_irq;
}
/* Set the clock scale and enable the event mode for CMP2 */
val = MFGPT_SCALE | (3 << 8);
cs5535_mfgpt_write(cs5535_event_clock, MFGPT_REG_SETUP, val);
/* Set up the clock event */
cs5535_clockevent.mult = div_sc(MFGPT_HZ, NSEC_PER_SEC,
cs5535_clockevent.shift);
cs5535_clockevent.min_delta_ns = clockevent_delta2ns(0xF,
&cs5535_clockevent);
cs5535_clockevent.max_delta_ns = clockevent_delta2ns(0xFFFE,
&cs5535_clockevent);
printk(KERN_INFO DRV_NAME
": Registering MFGPT timer as a clock event, using IRQ %d\n",
timer_irq);
clockevents_register_device(&cs5535_clockevent);
return 0;
err_irq:
cs5535_mfgpt_release_irq(cs5535_event_clock, MFGPT_CMP2, &timer_irq);
err_timer:
cs5535_mfgpt_free_timer(cs5535_event_clock);
printk(KERN_ERR DRV_NAME ": Unable to set up the MFGPT clock source\n");
return -EIO;
}
module_init(cs5535_mfgpt_init);
MODULE_AUTHOR("Andres Salomon <dilinger@queued.net>");
MODULE_DESCRIPTION("CS5535/CS5536 MFGPT clock event driver");
MODULE_LICENSE("GPL");
|
