linux-kernel - [PATCH] ARM: Delete ARM's own cnt32_to

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Message-ID: <20080926152258.29055.94270.stgit@warthog.procyon.org.uk>
Date:	Fri, 26 Sep 2008 16:22:58 +0100
From:	David Howells <dhowells@...hat.com>
To:	torvalds@...l.org, akpm@...ux-foundation.org
Cc:	dhowells@...hat.com, a.p.zijlstra@...llo.nl, nico@....org,
	linux-am33-list@...hat.com, linux-kernel@...r.kernel.org
Subject: [PATCH] ARM: Delete ARM's own cnt32_to_63.h

Delete ARM's own cnt32_to_63.h as the copy in include/linux/ should now be
used instead.

Signed-off-by: David Howells <dhowells@...hat.com>
---

 arch/arm/include/asm/cnt32_to_63.h |   78 ------------------------------------
 1 files changed, 0 insertions(+), 78 deletions(-)
 delete mode 100644 arch/arm/include/asm/cnt32_to_63.h


diff --git a/arch/arm/include/asm/cnt32_to_63.h b/arch/arm/include/asm/cnt32_to_63.h
deleted file mode 100644
index 480c873..0000000
--- a/arch/arm/include/asm/cnt32_to_63.h
+++ /dev/null
@@ -1,78 +0,0 @@
-/*
- *  include/asm/cnt32_to_63.h -- extend a 32-bit counter to 63 bits
- *
- *  Author:	Nicolas Pitre
- *  Created:	December 3, 2006
- *  Copyright:	MontaVista Software, Inc.
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2
- * as published by the Free Software Foundation.
- */
-
-#ifndef __INCLUDE_CNT32_TO_63_H__
-#define __INCLUDE_CNT32_TO_63_H__
-
-#include <linux/compiler.h>
-#include <asm/types.h>
-#include <asm/byteorder.h>
-
-/*
- * Prototype: u64 cnt32_to_63(u32 cnt)
- * Many hardware clock counters are only 32 bits wide and therefore have
- * a relatively short period making wrap-arounds rather frequent.  This
- * is a problem when implementing sched_clock() for example, where a 64-bit
- * non-wrapping monotonic value is expected to be returned.
- *
- * To overcome that limitation, let's extend a 32-bit counter to 63 bits
- * in a completely lock free fashion. Bits 0 to 31 of the clock are provided
- * by the hardware while bits 32 to 62 are stored in memory.  The top bit in
- * memory is used to synchronize with the hardware clock half-period.  When
- * the top bit of both counters (hardware and in memory) differ then the
- * memory is updated with a new value, incrementing it when the hardware
- * counter wraps around.
- *
- * Because a word store in memory is atomic then the incremented value will
- * always be in synch with the top bit indicating to any potential concurrent
- * reader if the value in memory is up to date or not with regards to the
- * needed increment.  And any race in updating the value in memory is harmless
- * as the same value would simply be stored more than once.
- *
- * The only restriction for the algorithm to work properly is that this
- * code must be executed at least once per each half period of the 32-bit
- * counter to properly update the state bit in memory. This is usually not a
- * problem in practice, but if it is then a kernel timer could be scheduled
- * to manage for this code to be executed often enough.
- *
- * Note that the top bit (bit 63) in the returned value should be considered
- * as garbage.  It is not cleared here because callers are likely to use a
- * multiplier on the returned value which can get rid of the top bit
- * implicitly by making the multiplier even, therefore saving on a runtime
- * clear-bit instruction. Otherwise caller must remember to clear the top
- * bit explicitly.
- */
-
-/* this is used only to give gcc a clue about good code generation */
-typedef union {
-	struct {
-#if defined(__LITTLE_ENDIAN)
-		u32 lo, hi;
-#elif defined(__BIG_ENDIAN)
-		u32 hi, lo;
-#endif
-	};
-	u64 val;
-} cnt32_to_63_t;
-
-#define cnt32_to_63(cnt_lo) \
-({ \
-	static volatile u32 __m_cnt_hi = 0; \
-	cnt32_to_63_t __x; \
-	__x.hi = __m_cnt_hi; \
-	__x.lo = (cnt_lo); \
- 	if (unlikely((s32)(__x.hi ^ __x.lo) < 0)) \
-		__m_cnt_hi = __x.hi = (__x.hi ^ 0x80000000) + (__x.hi >> 31); \
-	__x.val; \
-})
-
-#endif

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