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19#include <linux/clocksource.h>
20#include <linux/init.h>
21#include <linux/module.h>
22#include <linux/ioport.h>
23#include <linux/scx200.h>
24
25#define NAME "scx200_hrt"
26
27static int mhz27;
28module_param(mhz27, int, 0);
29MODULE_PARM_DESC(mhz27, "count at 27.0 MHz (default is 1.0 MHz)");
30
31static int ppm;
32module_param(ppm, int, 0);
33MODULE_PARM_DESC(ppm, "+-adjust to actual XO freq (ppm)");
34
35
36#define SCx200_TMCNFG_OFFSET (SCx200_TIMER_OFFSET + 5)
37
38
39#define HR_TMEN (1 << 0)
40#define HR_TMCLKSEL (1 << 1)
41#define HR_TM27MPD (1 << 2)
42
43
44#define HRT_FREQ 1000000
45
46static cycle_t read_hrt(struct clocksource *cs)
47{
48
49 return (cycle_t) inl(scx200_cb_base + SCx200_TIMER_OFFSET);
50}
51
52#define HRT_SHIFT_1 22
53#define HRT_SHIFT_27 26
54
55static struct clocksource cs_hrt = {
56 .name = "scx200_hrt",
57 .rating = 250,
58 .read = read_hrt,
59 .mask = CLOCKSOURCE_MASK(32),
60 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
61
62};
63
64static int __init init_hrt_clocksource(void)
65{
66
67 if (!scx200_cb_present())
68 return -ENODEV;
69
70
71 if (!request_region(scx200_cb_base + SCx200_TIMER_OFFSET,
72 SCx200_TIMER_SIZE,
73 "NatSemi SCx200 High-Resolution Timer")) {
74 printk(KERN_WARNING NAME ": unable to lock timer region\n");
75 return -ENODEV;
76 }
77
78
79 outb(HR_TMEN | (mhz27 ? HR_TMCLKSEL : 0),
80 scx200_cb_base + SCx200_TMCNFG_OFFSET);
81
82 if (mhz27) {
83 cs_hrt.shift = HRT_SHIFT_27;
84 cs_hrt.mult = clocksource_hz2mult((HRT_FREQ + ppm) * 27,
85 cs_hrt.shift);
86 } else {
87 cs_hrt.shift = HRT_SHIFT_1;
88 cs_hrt.mult = clocksource_hz2mult(HRT_FREQ + ppm,
89 cs_hrt.shift);
90 }
91 printk(KERN_INFO "enabling scx200 high-res timer (%s MHz +%d ppm)\n",
92 mhz27 ? "27":"1", ppm);
93
94 return clocksource_register(&cs_hrt);
95}
96
97module_init(init_hrt_clocksource);
98
99MODULE_AUTHOR("Jim Cromie <jim.cromie@gmail.com>");
100MODULE_DESCRIPTION("clocksource on SCx200 HiRes Timer");
101MODULE_LICENSE("GPL");
102