1#ifndef _LINUX_JIFFIES_H
2#define _LINUX_JIFFIES_H
3
4#include <linux/math64.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 Invalid value of HZ.
40#endif
41
42/* Suppose we want to divide two numbers NOM and DEN: NOM/DEN, then we can
43 * improve accuracy by shifting LSH bits, hence calculating:
44 *     (NOM << LSH) / DEN
45 * This however means trouble for large NOM, because (NOM << LSH) may no
46 * longer fit in 32 bits. The following way of calculating this gives us
47 * some slack, under the following conditions:
48 *   - (NOM / DEN) fits in (32 - LSH) bits.
49 *   - (NOM % DEN) fits in (32 - LSH) bits.
50 */
51#define SH_DIV(NOM,DEN,LSH) (   (((NOM) / (DEN)) << (LSH))              \
52                             + ((((NOM) % (DEN)) << (LSH)) + (DEN) / 2) / (DEN))
53
54/* LATCH is used in the interval timer and ftape setup. */
55#define LATCH ((CLOCK_TICK_RATE + HZ/2) / HZ)	/* For divider */
56
57extern int register_refined_jiffies(long clock_tick_rate);
58
59/* TICK_NSEC is the time between ticks in nsec assuming SHIFTED_HZ */
60#define TICK_NSEC ((NSEC_PER_SEC+HZ/2)/HZ)
61
62/* TICK_USEC is the time between ticks in usec assuming fake USER_HZ */
63#define TICK_USEC ((1000000UL + USER_HZ/2) / USER_HZ)
64
65/* some arch's have a small-data section that can be accessed register-relative
66 * but that can only take up to, say, 4-byte variables. jiffies being part of
67 * an 8-byte variable may not be correctly accessed unless we force the issue
68 */
69#define __jiffy_data  __attribute__((section(".data")))
70
71/*
72 * The 64-bit value is not atomic - you MUST NOT read it
73 * without sampling the sequence number in jiffies_lock.
74 * get_jiffies_64() will do this for you as appropriate.
75 */
76extern u64 __jiffy_data jiffies_64;
77extern unsigned long volatile __jiffy_data jiffies;
78
79#if (BITS_PER_LONG < 64)
80u64 get_jiffies_64(void);
81#else
82static inline u64 get_jiffies_64(void)
83{
84	return (u64)jiffies;
85}
86#endif
87
88/*
89 *	These inlines deal with timer wrapping correctly. You are
90 *	strongly encouraged to use them
91 *	1. Because people otherwise forget
92 *	2. Because if the timer wrap changes in future you won't have to
93 *	   alter your driver code.
94 *
95 * time_after(a,b) returns true if the time a is after time b.
96 *
97 * Do this with "<0" and ">=0" to only test the sign of the result. A
98 * good compiler would generate better code (and a really good compiler
99 * wouldn't care). Gcc is currently neither.
100 */
101#define time_after(a,b)		\
102	(typecheck(unsigned long, a) && \
103	 typecheck(unsigned long, b) && \
104	 ((long)((b) - (a)) < 0))
105#define time_before(a,b)	time_after(b,a)
106
107#define time_after_eq(a,b)	\
108	(typecheck(unsigned long, a) && \
109	 typecheck(unsigned long, b) && \
110	 ((long)((a) - (b)) >= 0))
111#define time_before_eq(a,b)	time_after_eq(b,a)
112
113/*
114 * Calculate whether a is in the range of [b, c].
115 */
116#define time_in_range(a,b,c) \
117	(time_after_eq(a,b) && \
118	 time_before_eq(a,c))
119
120/*
121 * Calculate whether a is in the range of [b, c).
122 */
123#define time_in_range_open(a,b,c) \
124	(time_after_eq(a,b) && \
125	 time_before(a,c))
126
127/* Same as above, but does so with platform independent 64bit types.
128 * These must be used when utilizing jiffies_64 (i.e. return value of
129 * get_jiffies_64() */
130#define time_after64(a,b)	\
131	(typecheck(__u64, a) &&	\
132	 typecheck(__u64, b) && \
133	 ((__s64)((b) - (a)) < 0))
134#define time_before64(a,b)	time_after64(b,a)
135
136#define time_after_eq64(a,b)	\
137	(typecheck(__u64, a) && \
138	 typecheck(__u64, b) && \
139	 ((__s64)((a) - (b)) >= 0))
140#define time_before_eq64(a,b)	time_after_eq64(b,a)
141
142#define time_in_range64(a, b, c) \
143	(time_after_eq64(a, b) && \
144	 time_before_eq64(a, c))
145
146/*
147 * These four macros compare jiffies and 'a' for convenience.
148 */
149
150/* time_is_before_jiffies(a) return true if a is before jiffies */
151#define time_is_before_jiffies(a) time_after(jiffies, a)
152
153/* time_is_after_jiffies(a) return true if a is after jiffies */
154#define time_is_after_jiffies(a) time_before(jiffies, a)
155
156/* time_is_before_eq_jiffies(a) return true if a is before or equal to jiffies*/
157#define time_is_before_eq_jiffies(a) time_after_eq(jiffies, a)
158
159/* time_is_after_eq_jiffies(a) return true if a is after or equal to jiffies*/
160#define time_is_after_eq_jiffies(a) time_before_eq(jiffies, a)
161
162/*
163 * Have the 32 bit jiffies value wrap 5 minutes after boot
164 * so jiffies wrap bugs show up earlier.
165 */
166#define INITIAL_JIFFIES ((unsigned long)(unsigned int) (-300*HZ))
167
168/*
169 * Change timeval to jiffies, trying to avoid the
170 * most obvious overflows..
171 *
172 * And some not so obvious.
173 *
174 * Note that we don't want to return LONG_MAX, because
175 * for various timeout reasons we often end up having
176 * to wait "jiffies+1" in order to guarantee that we wait
177 * at _least_ "jiffies" - so "jiffies+1" had better still
178 * be positive.
179 */
180#define MAX_JIFFY_OFFSET ((LONG_MAX >> 1)-1)
181
182extern unsigned long preset_lpj;
183
184/*
185 * We want to do realistic conversions of time so we need to use the same
186 * values the update wall clock code uses as the jiffies size.  This value
187 * is: TICK_NSEC (which is defined in timex.h).  This
188 * is a constant and is in nanoseconds.  We will use scaled math
189 * with a set of scales defined here as SEC_JIFFIE_SC,  USEC_JIFFIE_SC and
190 * NSEC_JIFFIE_SC.  Note that these defines contain nothing but
191 * constants and so are computed at compile time.  SHIFT_HZ (computed in
192 * timex.h) adjusts the scaling for different HZ values.
193
194 * Scaled math???  What is that?
195 *
196 * Scaled math is a way to do integer math on values that would,
197 * otherwise, either overflow, underflow, or cause undesired div
198 * instructions to appear in the execution path.  In short, we "scale"
199 * up the operands so they take more bits (more precision, less
200 * underflow), do the desired operation and then "scale" the result back
201 * by the same amount.  If we do the scaling by shifting we avoid the
202 * costly mpy and the dastardly div instructions.
203
204 * Suppose, for example, we want to convert from seconds to jiffies
205 * where jiffies is defined in nanoseconds as NSEC_PER_JIFFIE.  The
206 * simple math is: jiff = (sec * NSEC_PER_SEC) / NSEC_PER_JIFFIE; We
207 * observe that (NSEC_PER_SEC / NSEC_PER_JIFFIE) is a constant which we
208 * might calculate at compile time, however, the result will only have
209 * about 3-4 bits of precision (less for smaller values of HZ).
210 *
211 * So, we scale as follows:
212 * jiff = (sec) * (NSEC_PER_SEC / NSEC_PER_JIFFIE);
213 * jiff = ((sec) * ((NSEC_PER_SEC * SCALE)/ NSEC_PER_JIFFIE)) / SCALE;
214 * Then we make SCALE a power of two so:
215 * jiff = ((sec) * ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE)) >> SCALE;
216 * Now we define:
217 * #define SEC_CONV = ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE))
218 * jiff = (sec * SEC_CONV) >> SCALE;
219 *
220 * Often the math we use will expand beyond 32-bits so we tell C how to
221 * do this and pass the 64-bit result of the mpy through the ">> SCALE"
222 * which should take the result back to 32-bits.  We want this expansion
223 * to capture as much precision as possible.  At the same time we don't
224 * want to overflow so we pick the SCALE to avoid this.  In this file,
225 * that means using a different scale for each range of HZ values (as
226 * defined in timex.h).
227 *
228 * For those who want to know, gcc will give a 64-bit result from a "*"
229 * operator if the result is a long long AND at least one of the
230 * operands is cast to long long (usually just prior to the "*" so as
231 * not to confuse it into thinking it really has a 64-bit operand,
232 * which, buy the way, it can do, but it takes more code and at least 2
233 * mpys).
234
235 * We also need to be aware that one second in nanoseconds is only a
236 * couple of bits away from overflowing a 32-bit word, so we MUST use
237 * 64-bits to get the full range time in nanoseconds.
238
239 */
240
241/*
242 * Here are the scales we will use.  One for seconds, nanoseconds and
243 * microseconds.
244 *
245 * Within the limits of cpp we do a rough cut at the SEC_JIFFIE_SC and
246 * check if the sign bit is set.  If not, we bump the shift count by 1.
247 * (Gets an extra bit of precision where we can use it.)
248 * We know it is set for HZ = 1024 and HZ = 100 not for 1000.
249 * Haven't tested others.
250
251 * Limits of cpp (for #if expressions) only long (no long long), but
252 * then we only need the most signicant bit.
253 */
254
255#define SEC_JIFFIE_SC (31 - SHIFT_HZ)
256#if !((((NSEC_PER_SEC << 2) / TICK_NSEC) << (SEC_JIFFIE_SC - 2)) & 0x80000000)
257#undef SEC_JIFFIE_SC
258#define SEC_JIFFIE_SC (32 - SHIFT_HZ)
259#endif
260#define NSEC_JIFFIE_SC (SEC_JIFFIE_SC + 29)
261#define SEC_CONVERSION ((unsigned long)((((u64)NSEC_PER_SEC << SEC_JIFFIE_SC) +\
262                                TICK_NSEC -1) / (u64)TICK_NSEC))
263
264#define NSEC_CONVERSION ((unsigned long)((((u64)1 << NSEC_JIFFIE_SC) +\
265                                        TICK_NSEC -1) / (u64)TICK_NSEC))
266/*
267 * The maximum jiffie value is (MAX_INT >> 1).  Here we translate that
268 * into seconds.  The 64-bit case will overflow if we are not careful,
269 * so use the messy SH_DIV macro to do it.  Still all constants.
270 */
271#if BITS_PER_LONG < 64
272# define MAX_SEC_IN_JIFFIES \
273	(long)((u64)((u64)MAX_JIFFY_OFFSET * TICK_NSEC) / NSEC_PER_SEC)
274#else	/* take care of overflow on 64 bits machines */
275# define MAX_SEC_IN_JIFFIES \
276	(SH_DIV((MAX_JIFFY_OFFSET >> SEC_JIFFIE_SC) * TICK_NSEC, NSEC_PER_SEC, 1) - 1)
277
278#endif
279
280/*
281 * Convert various time units to each other:
282 */
283extern unsigned int jiffies_to_msecs(const unsigned long j);
284extern unsigned int jiffies_to_usecs(const unsigned long j);
285
286static inline u64 jiffies_to_nsecs(const unsigned long j)
287{
288	return (u64)jiffies_to_usecs(j) * NSEC_PER_USEC;
289}
290
291extern unsigned long msecs_to_jiffies(const unsigned int m);
292extern unsigned long usecs_to_jiffies(const unsigned int u);
293extern unsigned long timespec_to_jiffies(const struct timespec *value);
294extern void jiffies_to_timespec(const unsigned long jiffies,
295				struct timespec *value);
296extern unsigned long timeval_to_jiffies(const struct timeval *value);
297extern void jiffies_to_timeval(const unsigned long jiffies,
298			       struct timeval *value);
299
300extern clock_t jiffies_to_clock_t(unsigned long x);
301static inline clock_t jiffies_delta_to_clock_t(long delta)
302{
303	return jiffies_to_clock_t(max(0L, delta));
304}
305
306extern unsigned long clock_t_to_jiffies(unsigned long x);
307extern u64 jiffies_64_to_clock_t(u64 x);
308extern u64 nsec_to_clock_t(u64 x);
309extern u64 nsecs_to_jiffies64(u64 n);
310extern unsigned long nsecs_to_jiffies(u64 n);
311
312#define TIMESTAMP_SIZE	30
313
314#endif
315