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443 lines
15 KiB
443 lines
15 KiB
/* SPDX-License-Identifier: GPL-2.0 */ |
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#ifndef _LINUX_JIFFIES_H |
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#define _LINUX_JIFFIES_H |
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#include <linux/cache.h> |
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#include <linux/limits.h> |
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#include <linux/math64.h> |
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#include <linux/minmax.h> |
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#include <linux/types.h> |
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#include <linux/time.h> |
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#include <linux/timex.h> |
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#include <vdso/jiffies.h> |
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#include <asm/param.h> /* for HZ */ |
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#include <generated/timeconst.h> |
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/* |
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* The following defines establish the engineering parameters of the PLL |
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* model. The HZ variable establishes the timer interrupt frequency, 100 Hz |
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* for the SunOS kernel, 256 Hz for the Ultrix kernel and 1024 Hz for the |
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* OSF/1 kernel. The SHIFT_HZ define expresses the same value as the |
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* nearest power of two in order to avoid hardware multiply operations. |
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*/ |
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#if HZ >= 12 && HZ < 24 |
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# define SHIFT_HZ 4 |
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#elif HZ >= 24 && HZ < 48 |
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# define SHIFT_HZ 5 |
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#elif HZ >= 48 && HZ < 96 |
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# define SHIFT_HZ 6 |
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#elif HZ >= 96 && HZ < 192 |
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# define SHIFT_HZ 7 |
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#elif HZ >= 192 && HZ < 384 |
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# define SHIFT_HZ 8 |
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#elif HZ >= 384 && HZ < 768 |
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# define SHIFT_HZ 9 |
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#elif HZ >= 768 && HZ < 1536 |
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# define SHIFT_HZ 10 |
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#elif HZ >= 1536 && HZ < 3072 |
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# define SHIFT_HZ 11 |
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#elif HZ >= 3072 && HZ < 6144 |
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# define SHIFT_HZ 12 |
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#elif HZ >= 6144 && HZ < 12288 |
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# define SHIFT_HZ 13 |
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#else |
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# error Invalid value of HZ. |
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#endif |
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/* Suppose we want to divide two numbers NOM and DEN: NOM/DEN, then we can |
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* improve accuracy by shifting LSH bits, hence calculating: |
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* (NOM << LSH) / DEN |
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* This however means trouble for large NOM, because (NOM << LSH) may no |
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* longer fit in 32 bits. The following way of calculating this gives us |
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* some slack, under the following conditions: |
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* - (NOM / DEN) fits in (32 - LSH) bits. |
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* - (NOM % DEN) fits in (32 - LSH) bits. |
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*/ |
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#define SH_DIV(NOM,DEN,LSH) ( (((NOM) / (DEN)) << (LSH)) \ |
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+ ((((NOM) % (DEN)) << (LSH)) + (DEN) / 2) / (DEN)) |
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/* LATCH is used in the interval timer and ftape setup. */ |
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#define LATCH ((CLOCK_TICK_RATE + HZ/2) / HZ) /* For divider */ |
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extern int register_refined_jiffies(long clock_tick_rate); |
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/* TICK_USEC is the time between ticks in usec assuming SHIFTED_HZ */ |
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#define TICK_USEC ((USEC_PER_SEC + HZ/2) / HZ) |
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/* USER_TICK_USEC is the time between ticks in usec assuming fake USER_HZ */ |
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#define USER_TICK_USEC ((1000000UL + USER_HZ/2) / USER_HZ) |
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#ifndef __jiffy_arch_data |
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#define __jiffy_arch_data |
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#endif |
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/* |
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* The 64-bit value is not atomic - you MUST NOT read it |
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* without sampling the sequence number in jiffies_lock. |
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* get_jiffies_64() will do this for you as appropriate. |
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*/ |
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extern u64 __cacheline_aligned_in_smp jiffies_64; |
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extern unsigned long volatile __cacheline_aligned_in_smp __jiffy_arch_data jiffies; |
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#if (BITS_PER_LONG < 64) |
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u64 get_jiffies_64(void); |
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#else |
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static inline u64 get_jiffies_64(void) |
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{ |
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return (u64)jiffies; |
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} |
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#endif |
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/* |
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* These inlines deal with timer wrapping correctly. You are |
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* strongly encouraged to use them |
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* 1. Because people otherwise forget |
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* 2. Because if the timer wrap changes in future you won't have to |
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* alter your driver code. |
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* |
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* time_after(a,b) returns true if the time a is after time b. |
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* |
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* Do this with "<0" and ">=0" to only test the sign of the result. A |
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* good compiler would generate better code (and a really good compiler |
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* wouldn't care). Gcc is currently neither. |
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*/ |
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#define time_after(a,b) \ |
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(typecheck(unsigned long, a) && \ |
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typecheck(unsigned long, b) && \ |
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((long)((b) - (a)) < 0)) |
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#define time_before(a,b) time_after(b,a) |
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#define time_after_eq(a,b) \ |
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(typecheck(unsigned long, a) && \ |
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typecheck(unsigned long, b) && \ |
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((long)((a) - (b)) >= 0)) |
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#define time_before_eq(a,b) time_after_eq(b,a) |
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/* |
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* Calculate whether a is in the range of [b, c]. |
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*/ |
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#define time_in_range(a,b,c) \ |
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(time_after_eq(a,b) && \ |
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time_before_eq(a,c)) |
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/* |
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* Calculate whether a is in the range of [b, c). |
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*/ |
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#define time_in_range_open(a,b,c) \ |
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(time_after_eq(a,b) && \ |
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time_before(a,c)) |
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/* Same as above, but does so with platform independent 64bit types. |
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* These must be used when utilizing jiffies_64 (i.e. return value of |
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* get_jiffies_64() */ |
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#define time_after64(a,b) \ |
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(typecheck(__u64, a) && \ |
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typecheck(__u64, b) && \ |
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((__s64)((b) - (a)) < 0)) |
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#define time_before64(a,b) time_after64(b,a) |
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#define time_after_eq64(a,b) \ |
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(typecheck(__u64, a) && \ |
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typecheck(__u64, b) && \ |
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((__s64)((a) - (b)) >= 0)) |
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#define time_before_eq64(a,b) time_after_eq64(b,a) |
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#define time_in_range64(a, b, c) \ |
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(time_after_eq64(a, b) && \ |
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time_before_eq64(a, c)) |
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/* |
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* These four macros compare jiffies and 'a' for convenience. |
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*/ |
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/* time_is_before_jiffies(a) return true if a is before jiffies */ |
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#define time_is_before_jiffies(a) time_after(jiffies, a) |
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#define time_is_before_jiffies64(a) time_after64(get_jiffies_64(), a) |
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/* time_is_after_jiffies(a) return true if a is after jiffies */ |
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#define time_is_after_jiffies(a) time_before(jiffies, a) |
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#define time_is_after_jiffies64(a) time_before64(get_jiffies_64(), a) |
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/* time_is_before_eq_jiffies(a) return true if a is before or equal to jiffies*/ |
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#define time_is_before_eq_jiffies(a) time_after_eq(jiffies, a) |
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#define time_is_before_eq_jiffies64(a) time_after_eq64(get_jiffies_64(), a) |
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/* time_is_after_eq_jiffies(a) return true if a is after or equal to jiffies*/ |
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#define time_is_after_eq_jiffies(a) time_before_eq(jiffies, a) |
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#define time_is_after_eq_jiffies64(a) time_before_eq64(get_jiffies_64(), a) |
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/* |
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* Have the 32 bit jiffies value wrap 5 minutes after boot |
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* so jiffies wrap bugs show up earlier. |
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*/ |
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#define INITIAL_JIFFIES ((unsigned long)(unsigned int) (-300*HZ)) |
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/* |
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* Change timeval to jiffies, trying to avoid the |
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* most obvious overflows.. |
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* |
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* And some not so obvious. |
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* |
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* Note that we don't want to return LONG_MAX, because |
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* for various timeout reasons we often end up having |
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* to wait "jiffies+1" in order to guarantee that we wait |
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* at _least_ "jiffies" - so "jiffies+1" had better still |
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* be positive. |
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*/ |
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#define MAX_JIFFY_OFFSET ((LONG_MAX >> 1)-1) |
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extern unsigned long preset_lpj; |
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/* |
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* We want to do realistic conversions of time so we need to use the same |
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* values the update wall clock code uses as the jiffies size. This value |
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* is: TICK_NSEC (which is defined in timex.h). This |
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* is a constant and is in nanoseconds. We will use scaled math |
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* with a set of scales defined here as SEC_JIFFIE_SC, USEC_JIFFIE_SC and |
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* NSEC_JIFFIE_SC. Note that these defines contain nothing but |
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* constants and so are computed at compile time. SHIFT_HZ (computed in |
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* timex.h) adjusts the scaling for different HZ values. |
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* Scaled math??? What is that? |
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* |
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* Scaled math is a way to do integer math on values that would, |
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* otherwise, either overflow, underflow, or cause undesired div |
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* instructions to appear in the execution path. In short, we "scale" |
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* up the operands so they take more bits (more precision, less |
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* underflow), do the desired operation and then "scale" the result back |
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* by the same amount. If we do the scaling by shifting we avoid the |
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* costly mpy and the dastardly div instructions. |
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* Suppose, for example, we want to convert from seconds to jiffies |
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* where jiffies is defined in nanoseconds as NSEC_PER_JIFFIE. The |
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* simple math is: jiff = (sec * NSEC_PER_SEC) / NSEC_PER_JIFFIE; We |
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* observe that (NSEC_PER_SEC / NSEC_PER_JIFFIE) is a constant which we |
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* might calculate at compile time, however, the result will only have |
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* about 3-4 bits of precision (less for smaller values of HZ). |
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* |
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* So, we scale as follows: |
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* jiff = (sec) * (NSEC_PER_SEC / NSEC_PER_JIFFIE); |
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* jiff = ((sec) * ((NSEC_PER_SEC * SCALE)/ NSEC_PER_JIFFIE)) / SCALE; |
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* Then we make SCALE a power of two so: |
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* jiff = ((sec) * ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE)) >> SCALE; |
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* Now we define: |
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* #define SEC_CONV = ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE)) |
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* jiff = (sec * SEC_CONV) >> SCALE; |
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* |
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* Often the math we use will expand beyond 32-bits so we tell C how to |
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* do this and pass the 64-bit result of the mpy through the ">> SCALE" |
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* which should take the result back to 32-bits. We want this expansion |
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* to capture as much precision as possible. At the same time we don't |
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* want to overflow so we pick the SCALE to avoid this. In this file, |
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* that means using a different scale for each range of HZ values (as |
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* defined in timex.h). |
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* |
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* For those who want to know, gcc will give a 64-bit result from a "*" |
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* operator if the result is a long long AND at least one of the |
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* operands is cast to long long (usually just prior to the "*" so as |
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* not to confuse it into thinking it really has a 64-bit operand, |
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* which, buy the way, it can do, but it takes more code and at least 2 |
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* mpys). |
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* We also need to be aware that one second in nanoseconds is only a |
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* couple of bits away from overflowing a 32-bit word, so we MUST use |
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* 64-bits to get the full range time in nanoseconds. |
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*/ |
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/* |
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* Here are the scales we will use. One for seconds, nanoseconds and |
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* microseconds. |
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* |
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* Within the limits of cpp we do a rough cut at the SEC_JIFFIE_SC and |
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* check if the sign bit is set. If not, we bump the shift count by 1. |
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* (Gets an extra bit of precision where we can use it.) |
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* We know it is set for HZ = 1024 and HZ = 100 not for 1000. |
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* Haven't tested others. |
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* Limits of cpp (for #if expressions) only long (no long long), but |
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* then we only need the most signicant bit. |
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*/ |
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#define SEC_JIFFIE_SC (31 - SHIFT_HZ) |
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#if !((((NSEC_PER_SEC << 2) / TICK_NSEC) << (SEC_JIFFIE_SC - 2)) & 0x80000000) |
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#undef SEC_JIFFIE_SC |
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#define SEC_JIFFIE_SC (32 - SHIFT_HZ) |
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#endif |
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#define NSEC_JIFFIE_SC (SEC_JIFFIE_SC + 29) |
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#define SEC_CONVERSION ((unsigned long)((((u64)NSEC_PER_SEC << SEC_JIFFIE_SC) +\ |
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TICK_NSEC -1) / (u64)TICK_NSEC)) |
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#define NSEC_CONVERSION ((unsigned long)((((u64)1 << NSEC_JIFFIE_SC) +\ |
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TICK_NSEC -1) / (u64)TICK_NSEC)) |
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/* |
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* The maximum jiffie value is (MAX_INT >> 1). Here we translate that |
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* into seconds. The 64-bit case will overflow if we are not careful, |
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* so use the messy SH_DIV macro to do it. Still all constants. |
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*/ |
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#if BITS_PER_LONG < 64 |
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# define MAX_SEC_IN_JIFFIES \ |
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(long)((u64)((u64)MAX_JIFFY_OFFSET * TICK_NSEC) / NSEC_PER_SEC) |
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#else /* take care of overflow on 64 bits machines */ |
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# define MAX_SEC_IN_JIFFIES \ |
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(SH_DIV((MAX_JIFFY_OFFSET >> SEC_JIFFIE_SC) * TICK_NSEC, NSEC_PER_SEC, 1) - 1) |
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#endif |
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/* |
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* Convert various time units to each other: |
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*/ |
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extern unsigned int jiffies_to_msecs(const unsigned long j); |
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extern unsigned int jiffies_to_usecs(const unsigned long j); |
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static inline u64 jiffies_to_nsecs(const unsigned long j) |
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{ |
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return (u64)jiffies_to_usecs(j) * NSEC_PER_USEC; |
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} |
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extern u64 jiffies64_to_nsecs(u64 j); |
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extern u64 jiffies64_to_msecs(u64 j); |
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extern unsigned long __msecs_to_jiffies(const unsigned int m); |
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#if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ) |
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/* |
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* HZ is equal to or smaller than 1000, and 1000 is a nice round |
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* multiple of HZ, divide with the factor between them, but round |
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* upwards: |
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*/ |
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static inline unsigned long _msecs_to_jiffies(const unsigned int m) |
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{ |
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return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ); |
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} |
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#elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC) |
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/* |
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* HZ is larger than 1000, and HZ is a nice round multiple of 1000 - |
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* simply multiply with the factor between them. |
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* |
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* But first make sure the multiplication result cannot overflow: |
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*/ |
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static inline unsigned long _msecs_to_jiffies(const unsigned int m) |
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{ |
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if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET)) |
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return MAX_JIFFY_OFFSET; |
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return m * (HZ / MSEC_PER_SEC); |
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} |
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#else |
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/* |
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* Generic case - multiply, round and divide. But first check that if |
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* we are doing a net multiplication, that we wouldn't overflow: |
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*/ |
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static inline unsigned long _msecs_to_jiffies(const unsigned int m) |
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{ |
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if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET)) |
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return MAX_JIFFY_OFFSET; |
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return (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32) >> MSEC_TO_HZ_SHR32; |
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} |
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#endif |
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/** |
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* msecs_to_jiffies: - convert milliseconds to jiffies |
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* @m: time in milliseconds |
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* |
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* conversion is done as follows: |
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* |
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* - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET) |
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* |
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* - 'too large' values [that would result in larger than |
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* MAX_JIFFY_OFFSET values] mean 'infinite timeout' too. |
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* |
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* - all other values are converted to jiffies by either multiplying |
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* the input value by a factor or dividing it with a factor and |
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* handling any 32-bit overflows. |
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* for the details see __msecs_to_jiffies() |
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* |
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* msecs_to_jiffies() checks for the passed in value being a constant |
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* via __builtin_constant_p() allowing gcc to eliminate most of the |
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* code, __msecs_to_jiffies() is called if the value passed does not |
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* allow constant folding and the actual conversion must be done at |
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* runtime. |
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* the HZ range specific helpers _msecs_to_jiffies() are called both |
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* directly here and from __msecs_to_jiffies() in the case where |
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* constant folding is not possible. |
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*/ |
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static __always_inline unsigned long msecs_to_jiffies(const unsigned int m) |
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{ |
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if (__builtin_constant_p(m)) { |
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if ((int)m < 0) |
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return MAX_JIFFY_OFFSET; |
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return _msecs_to_jiffies(m); |
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} else { |
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return __msecs_to_jiffies(m); |
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} |
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} |
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extern unsigned long __usecs_to_jiffies(const unsigned int u); |
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#if !(USEC_PER_SEC % HZ) |
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static inline unsigned long _usecs_to_jiffies(const unsigned int u) |
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{ |
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return (u + (USEC_PER_SEC / HZ) - 1) / (USEC_PER_SEC / HZ); |
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} |
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#else |
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static inline unsigned long _usecs_to_jiffies(const unsigned int u) |
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{ |
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return (USEC_TO_HZ_MUL32 * u + USEC_TO_HZ_ADJ32) |
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>> USEC_TO_HZ_SHR32; |
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} |
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#endif |
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/** |
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* usecs_to_jiffies: - convert microseconds to jiffies |
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* @u: time in microseconds |
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* |
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* conversion is done as follows: |
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* |
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* - 'too large' values [that would result in larger than |
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* MAX_JIFFY_OFFSET values] mean 'infinite timeout' too. |
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* |
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* - all other values are converted to jiffies by either multiplying |
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* the input value by a factor or dividing it with a factor and |
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* handling any 32-bit overflows as for msecs_to_jiffies. |
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* |
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* usecs_to_jiffies() checks for the passed in value being a constant |
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* via __builtin_constant_p() allowing gcc to eliminate most of the |
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* code, __usecs_to_jiffies() is called if the value passed does not |
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* allow constant folding and the actual conversion must be done at |
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* runtime. |
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* the HZ range specific helpers _usecs_to_jiffies() are called both |
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* directly here and from __msecs_to_jiffies() in the case where |
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* constant folding is not possible. |
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*/ |
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static __always_inline unsigned long usecs_to_jiffies(const unsigned int u) |
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{ |
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if (__builtin_constant_p(u)) { |
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if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET)) |
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return MAX_JIFFY_OFFSET; |
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return _usecs_to_jiffies(u); |
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} else { |
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return __usecs_to_jiffies(u); |
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} |
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} |
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extern unsigned long timespec64_to_jiffies(const struct timespec64 *value); |
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extern void jiffies_to_timespec64(const unsigned long jiffies, |
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struct timespec64 *value); |
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extern clock_t jiffies_to_clock_t(unsigned long x); |
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static inline clock_t jiffies_delta_to_clock_t(long delta) |
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{ |
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return jiffies_to_clock_t(max(0L, delta)); |
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} |
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static inline unsigned int jiffies_delta_to_msecs(long delta) |
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{ |
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return jiffies_to_msecs(max(0L, delta)); |
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} |
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extern unsigned long clock_t_to_jiffies(unsigned long x); |
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extern u64 jiffies_64_to_clock_t(u64 x); |
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extern u64 nsec_to_clock_t(u64 x); |
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extern u64 nsecs_to_jiffies64(u64 n); |
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extern unsigned long nsecs_to_jiffies(u64 n); |
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#define TIMESTAMP_SIZE 30 |
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#endif
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