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1#ifndef _LINUX_JIFFIES_H
2#define _LINUX_JIFFIES_H
3
4#include <linux/calc64.h>
5#include <linux/kernel.h>
6#include <linux/types.h>
7#include <linux/time.h>
8#include <linux/timex.h>
9#include <asm/param.h> /* for HZ */
10
11/*
12 * The following defines establish the engineering parameters of the PLL
13 * model. The HZ variable establishes the timer interrupt frequency, 100 Hz
14 * for the SunOS kernel, 256 Hz for the Ultrix kernel and 1024 Hz for the
15 * OSF/1 kernel. The SHIFT_HZ define expresses the same value as the
16 * nearest power of two in order to avoid hardware multiply operations.
17 */
18#if HZ >= 12 && HZ < 24
19# define SHIFT_HZ 4
20#elif HZ >= 24 && HZ < 48
21# define SHIFT_HZ 5
22#elif HZ >= 48 && HZ < 96
23# define SHIFT_HZ 6
24#elif HZ >= 96 && HZ < 192
25# define SHIFT_HZ 7
26#elif HZ >= 192 && HZ < 384
27# define SHIFT_HZ 8
28#elif HZ >= 384 && HZ < 768
29# define SHIFT_HZ 9
30#elif HZ >= 768 && HZ < 1536
31# define SHIFT_HZ 10
32#elif HZ >= 1536 && HZ < 3072
33# define SHIFT_HZ 11
34#elif HZ >= 3072 && HZ < 6144
35# define SHIFT_HZ 12
36#elif HZ >= 6144 && HZ < 12288
37# define SHIFT_HZ 13
38#else
39# error You lose.
40#endif
41
42/* LATCH is used in the interval timer and ftape setup. */
43#define LATCH ((CLOCK_TICK_RATE + HZ/2) / HZ) /* For divider */
44
45/* Suppose we want to devide two numbers NOM and DEN: NOM/DEN, the we can
46 * improve accuracy by shifting LSH bits, hence calculating:
47 * (NOM << LSH) / DEN
48 * This however means trouble for large NOM, because (NOM << LSH) may no
49 * longer fit in 32 bits. The following way of calculating this gives us
50 * some slack, under the following conditions:
51 * - (NOM / DEN) fits in (32 - LSH) bits.
52 * - (NOM % DEN) fits in (32 - LSH) bits.
53 */
54#define SH_DIV(NOM,DEN,LSH) ( (((NOM) / (DEN)) << (LSH)) \
55 + ((((NOM) % (DEN)) << (LSH)) + (DEN) / 2) / (DEN))
56
57/* HZ is the requested value. ACTHZ is actual HZ ("<< 8" is for accuracy) */
58#define ACTHZ (SH_DIV (CLOCK_TICK_RATE, LATCH, 8))
59
60/* TICK_NSEC is the time between ticks in nsec assuming real ACTHZ */
61#define TICK_NSEC (SH_DIV (1000000UL * 1000, ACTHZ, 8))
62
63/* TICK_USEC is the time between ticks in usec assuming fake USER_HZ */
64#define TICK_USEC ((1000000UL + USER_HZ/2) / USER_HZ)
65
66/* TICK_USEC_TO_NSEC is the time between ticks in nsec assuming real ACTHZ and */
67/* a value TUSEC for TICK_USEC (can be set bij adjtimex) */
68#define TICK_USEC_TO_NSEC(TUSEC) (SH_DIV (TUSEC * USER_HZ * 1000, ACTHZ, 8))
69
70/* some arch's have a small-data section that can be accessed register-relative
71 * but that can only take up to, say, 4-byte variables. jiffies being part of
72 * an 8-byte variable may not be correctly accessed unless we force the issue
73 */
74#define __jiffy_data __attribute__((section(".data")))
75
76/*
77 * The 64-bit value is not atomic - you MUST NOT read it
78 * without sampling the sequence number in xtime_lock.
79 * get_jiffies_64() will do this for you as appropriate.
80 */
81extern u64 __jiffy_data jiffies_64;
82extern unsigned long volatile __jiffy_data jiffies;
83
84#if (BITS_PER_LONG < 64)
85u64 get_jiffies_64(void);
86#else
87static inline u64 get_jiffies_64(void)
88{
89 return (u64)jiffies;
90}
91#endif
92
93/*
94 * These inlines deal with timer wrapping correctly. You are
95 * strongly encouraged to use them
96 * 1. Because people otherwise forget
97 * 2. Because if the timer wrap changes in future you won't have to
98 * alter your driver code.
99 *
100 * time_after(a,b) returns true if the time a is after time b.
101 *
102 * Do this with "<0" and ">=0" to only test the sign of the result. A
103 * good compiler would generate better code (and a really good compiler
104 * wouldn't care). Gcc is currently neither.
105 */
106#define time_after(a,b) \
107 (typecheck(unsigned long, a) && \
108 typecheck(unsigned long, b) && \
109 ((long)(b) - (long)(a) < 0))
110#define time_before(a,b) time_after(b,a)
111
112#define time_after_eq(a,b) \
113 (typecheck(unsigned long, a) && \
114 typecheck(unsigned long, b) && \
115 ((long)(a) - (long)(b) >= 0))
116#define time_before_eq(a,b) time_after_eq(b,a)
117
118#define time_in_range(a,b,c) \
119 (time_after_eq(a,b) && \
120 time_before_eq(a,c))
121
122/* Same as above, but does so with platform independent 64bit types.
123 * These must be used when utilizing jiffies_64 (i.e. return value of
124 * get_jiffies_64() */
125#define time_after64(a,b) \
126 (typecheck(__u64, a) && \
127 typecheck(__u64, b) && \
128 ((__s64)(b) - (__s64)(a) < 0))
129#define time_before64(a,b) time_after64(b,a)
130
131#define time_after_eq64(a,b) \
132 (typecheck(__u64, a) && \
133 typecheck(__u64, b) && \
134 ((__s64)(a) - (__s64)(b) >= 0))
135#define time_before_eq64(a,b) time_after_eq64(b,a)
136
137/*
138 * Have the 32 bit jiffies value wrap 5 minutes after boot
139 * so jiffies wrap bugs show up earlier.
140 */
141#define INITIAL_JIFFIES ((unsigned long)(unsigned int) (-300*HZ))
142
143/*
144 * Change timeval to jiffies, trying to avoid the
145 * most obvious overflows..
146 *
147 * And some not so obvious.
148 *
149 * Note that we don't want to return LONG_MAX, because
150 * for various timeout reasons we often end up having
151 * to wait "jiffies+1" in order to guarantee that we wait
152 * at _least_ "jiffies" - so "jiffies+1" had better still
153 * be positive.
154 */
155#define MAX_JIFFY_OFFSET ((LONG_MAX >> 1)-1)
156
157extern unsigned long preset_lpj;
158
159/*
160 * We want to do realistic conversions of time so we need to use the same
161 * values the update wall clock code uses as the jiffies size. This value
162 * is: TICK_NSEC (which is defined in timex.h). This
163 * is a constant and is in nanoseconds. We will used scaled math
164 * with a set of scales defined here as SEC_JIFFIE_SC, USEC_JIFFIE_SC and
165 * NSEC_JIFFIE_SC. Note that these defines contain nothing but
166 * constants and so are computed at compile time. SHIFT_HZ (computed in
167 * timex.h) adjusts the scaling for different HZ values.
168
169 * Scaled math??? What is that?
170 *
171 * Scaled math is a way to do integer math on values that would,
172 * otherwise, either overflow, underflow, or cause undesired div
173 * instructions to appear in the execution path. In short, we "scale"
174 * up the operands so they take more bits (more precision, less
175 * underflow), do the desired operation and then "scale" the result back
176 * by the same amount. If we do the scaling by shifting we avoid the
177 * costly mpy and the dastardly div instructions.
178
179 * Suppose, for example, we want to convert from seconds to jiffies
180 * where jiffies is defined in nanoseconds as NSEC_PER_JIFFIE. The
181 * simple math is: jiff = (sec * NSEC_PER_SEC) / NSEC_PER_JIFFIE; We
182 * observe that (NSEC_PER_SEC / NSEC_PER_JIFFIE) is a constant which we
183 * might calculate at compile time, however, the result will only have
184 * about 3-4 bits of precision (less for smaller values of HZ).
185 *
186 * So, we scale as follows:
187 * jiff = (sec) * (NSEC_PER_SEC / NSEC_PER_JIFFIE);
188 * jiff = ((sec) * ((NSEC_PER_SEC * SCALE)/ NSEC_PER_JIFFIE)) / SCALE;
189 * Then we make SCALE a power of two so:
190 * jiff = ((sec) * ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE)) >> SCALE;
191 * Now we define:
192 * #define SEC_CONV = ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE))
193 * jiff = (sec * SEC_CONV) >> SCALE;
194 *
195 * Often the math we use will expand beyond 32-bits so we tell C how to
196 * do this and pass the 64-bit result of the mpy through the ">> SCALE"
197 * which should take the result back to 32-bits. We want this expansion
198 * to capture as much precision as possible. At the same time we don't
199 * want to overflow so we pick the SCALE to avoid this. In this file,
200 * that means using a different scale for each range of HZ values (as
201 * defined in timex.h).
202 *
203 * For those who want to know, gcc will give a 64-bit result from a "*"
204 * operator if the result is a long long AND at least one of the
205 * operands is cast to long long (usually just prior to the "*" so as
206 * not to confuse it into thinking it really has a 64-bit operand,
207 * which, buy the way, it can do, but it take more code and at least 2
208 * mpys).
209
210 * We also need to be aware that one second in nanoseconds is only a
211 * couple of bits away from overflowing a 32-bit word, so we MUST use
212 * 64-bits to get the full range time in nanoseconds.
213
214 */
215
216/*
217 * Here are the scales we will use. One for seconds, nanoseconds and
218 * microseconds.
219 *
220 * Within the limits of cpp we do a rough cut at the SEC_JIFFIE_SC and
221 * check if the sign bit is set. If not, we bump the shift count by 1.
222 * (Gets an extra bit of precision where we can use it.)
223 * We know it is set for HZ = 1024 and HZ = 100 not for 1000.
224 * Haven't tested others.
225
226 * Limits of cpp (for #if expressions) only long (no long long), but
227 * then we only need the most signicant bit.
228 */
229
230#define SEC_JIFFIE_SC (31 - SHIFT_HZ)
231#if !((((NSEC_PER_SEC << 2) / TICK_NSEC) << (SEC_JIFFIE_SC - 2)) & 0x80000000)
232#undef SEC_JIFFIE_SC
233#define SEC_JIFFIE_SC (32 - SHIFT_HZ)
234#endif
235#define NSEC_JIFFIE_SC (SEC_JIFFIE_SC + 29)
236#define USEC_JIFFIE_SC (SEC_JIFFIE_SC + 19)
237#define SEC_CONVERSION ((unsigned long)((((u64)NSEC_PER_SEC << SEC_JIFFIE_SC) +\
238 TICK_NSEC -1) / (u64)TICK_NSEC))
239
240#define NSEC_CONVERSION ((unsigned long)((((u64)1 << NSEC_JIFFIE_SC) +\
241 TICK_NSEC -1) / (u64)TICK_NSEC))
242#define USEC_CONVERSION \
243 ((unsigned long)((((u64)NSEC_PER_USEC << USEC_JIFFIE_SC) +\
244 TICK_NSEC -1) / (u64)TICK_NSEC))
245/*
246 * USEC_ROUND is used in the timeval to jiffie conversion. See there
247 * for more details. It is the scaled resolution rounding value. Note
248 * that it is a 64-bit value. Since, when it is applied, we are already
249 * in jiffies (albit scaled), it is nothing but the bits we will shift
250 * off.
251 */
252#define USEC_ROUND (u64)(((u64)1 << USEC_JIFFIE_SC) - 1)
253/*
254 * The maximum jiffie value is (MAX_INT >> 1). Here we translate that
255 * into seconds. The 64-bit case will overflow if we are not careful,
256 * so use the messy SH_DIV macro to do it. Still all constants.
257 */
258#if BITS_PER_LONG < 64
259# define MAX_SEC_IN_JIFFIES \
260 (long)((u64)((u64)MAX_JIFFY_OFFSET * TICK_NSEC) / NSEC_PER_SEC)
261#else /* take care of overflow on 64 bits machines */
262# define MAX_SEC_IN_JIFFIES \
263 (SH_DIV((MAX_JIFFY_OFFSET >> SEC_JIFFIE_SC) * TICK_NSEC, NSEC_PER_SEC, 1) - 1)
264
265#endif
266
267/*
268 * Convert various time units to each other:
269 */
270extern unsigned int jiffies_to_msecs(const unsigned long j);
271extern unsigned int jiffies_to_usecs(const unsigned long j);
272extern unsigned long msecs_to_jiffies(const unsigned int m);
273extern unsigned long usecs_to_jiffies(const unsigned int u);
274extern unsigned long timespec_to_jiffies(const struct timespec *value);
275extern void jiffies_to_timespec(const unsigned long jiffies,
276 struct timespec *value);
277extern unsigned long timeval_to_jiffies(const struct timeval *value);
278extern void jiffies_to_timeval(const unsigned long jiffies,
279 struct timeval *value);
280extern clock_t jiffies_to_clock_t(long x);
281extern unsigned long clock_t_to_jiffies(unsigned long x);
282extern u64 jiffies_64_to_clock_t(u64 x);
283extern u64 nsec_to_clock_t(u64 x);
284
285#define TIMESTAMP_SIZE 30
286
287#endif