Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
MN10300: Move asm-arm/cnt32_to_63.h to include/linux/
Move asm-arm/cnt32_to_63.h to include/linux/ so that MN10300 can make
use of it too.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
authored by
David Howells
and committed by
Linus Torvalds
b4f151ff
7a528159
+83
-3
+1
-1
arch/arm/mach-pxa/time.c
+1
-1
arch/arm/mach-pxa/time.c
···
17
17
#include <linux/interrupt.h>
18
18
#include <linux/clockchips.h>
19
19
#include <linux/sched.h>
20
+
#include <linux/cnt32_to_63.h>
20
21
21
22
#include <asm/div64.h>
22
-
#include <asm/cnt32_to_63.h>
23
23
#include <asm/mach/irq.h>
24
24
#include <asm/mach/time.h>
25
25
#include <mach/pxa-regs.h>
+1
-1
arch/arm/mach-sa1100/generic.c
+1
-1
arch/arm/mach-sa1100/generic.c
···
18
18
#include <linux/ioport.h>
19
19
#include <linux/sched.h> /* just for sched_clock() - funny that */
20
20
#include <linux/platform_device.h>
21
+
#include <linux/cnt32_to_63.h>
21
22
22
23
#include <asm/div64.h>
23
-
#include <asm/cnt32_to_63.h>
24
24
#include <mach/hardware.h>
25
25
#include <asm/system.h>
26
26
#include <asm/pgtable.h>
+1
-1
arch/arm/mach-versatile/core.c
+1
-1
arch/arm/mach-versatile/core.c
+80
include/linux/cnt32_to_63.h
+80
include/linux/cnt32_to_63.h
···
1
+
/*
2
+
* Extend a 32-bit counter to 63 bits
3
+
*
4
+
* Author: Nicolas Pitre
5
+
* Created: December 3, 2006
6
+
* Copyright: MontaVista Software, Inc.
7
+
*
8
+
* This program is free software; you can redistribute it and/or modify
9
+
* it under the terms of the GNU General Public License version 2
10
+
* as published by the Free Software Foundation.
11
+
*/
12
+
13
+
#ifndef __LINUX_CNT32_TO_63_H__
14
+
#define __LINUX_CNT32_TO_63_H__
15
+
16
+
#include <linux/compiler.h>
17
+
#include <linux/types.h>
18
+
#include <asm/byteorder.h>
19
+
20
+
/* this is used only to give gcc a clue about good code generation */
21
+
union cnt32_to_63 {
22
+
struct {
23
+
#if defined(__LITTLE_ENDIAN)
24
+
u32 lo, hi;
25
+
#elif defined(__BIG_ENDIAN)
26
+
u32 hi, lo;
27
+
#endif
28
+
};
29
+
u64 val;
30
+
};
31
+
32
+
33
+
/**
34
+
* cnt32_to_63 - Expand a 32-bit counter to a 63-bit counter
35
+
* @cnt_lo: The low part of the counter
36
+
*
37
+
* Many hardware clock counters are only 32 bits wide and therefore have
38
+
* a relatively short period making wrap-arounds rather frequent. This
39
+
* is a problem when implementing sched_clock() for example, where a 64-bit
40
+
* non-wrapping monotonic value is expected to be returned.
41
+
*
42
+
* To overcome that limitation, let's extend a 32-bit counter to 63 bits
43
+
* in a completely lock free fashion. Bits 0 to 31 of the clock are provided
44
+
* by the hardware while bits 32 to 62 are stored in memory. The top bit in
45
+
* memory is used to synchronize with the hardware clock half-period. When
46
+
* the top bit of both counters (hardware and in memory) differ then the
47
+
* memory is updated with a new value, incrementing it when the hardware
48
+
* counter wraps around.
49
+
*
50
+
* Because a word store in memory is atomic then the incremented value will
51
+
* always be in synch with the top bit indicating to any potential concurrent
52
+
* reader if the value in memory is up to date or not with regards to the
53
+
* needed increment. And any race in updating the value in memory is harmless
54
+
* as the same value would simply be stored more than once.
55
+
*
56
+
* The only restriction for the algorithm to work properly is that this
57
+
* code must be executed at least once per each half period of the 32-bit
58
+
* counter to properly update the state bit in memory. This is usually not a
59
+
* problem in practice, but if it is then a kernel timer could be scheduled
60
+
* to manage for this code to be executed often enough.
61
+
*
62
+
* Note that the top bit (bit 63) in the returned value should be considered
63
+
* as garbage. It is not cleared here because callers are likely to use a
64
+
* multiplier on the returned value which can get rid of the top bit
65
+
* implicitly by making the multiplier even, therefore saving on a runtime
66
+
* clear-bit instruction. Otherwise caller must remember to clear the top
67
+
* bit explicitly.
68
+
*/
69
+
#define cnt32_to_63(cnt_lo) \
70
+
({ \
71
+
static volatile u32 __m_cnt_hi; \
72
+
union cnt32_to_63 __x; \
73
+
__x.hi = __m_cnt_hi; \
74
+
__x.lo = (cnt_lo); \
75
+
if (unlikely((s32)(__x.hi ^ __x.lo) < 0)) \
76
+
__m_cnt_hi = __x.hi = (__x.hi ^ 0x80000000) + (__x.hi >> 31); \
77
+
__x.val; \
78
+
})
79
+
80
+
#endif