linux-kernel - [PATCH 2/2] Convert PowerPC macro spin_event_timeout() to architecture independent macro

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Date:	Tue, 30 Jul 2013 18:08:20 +0530
From:	Arpit Goel <B44344@...escale.com>
To:	<linux@....linux.org.uk>, <takata@...ux-m32r.org>, <philb@....org>,
	<geert@...ux-m68k.org>, <schwidefsky@...ibm.com>,
	<heiko.carstens@...ibm.com>, <linux390@...ibm.com>,
	<davem@...emloft.net>, <rob.herring@...xeda.com>, <arnd@...db.de>,
	<sboyd@...eaurora.org>, <swarren@...dia.com>,
	<john.stultz@...aro.org>, <jesper.nilsson@...s.com>,
	<gregkh@...uxfoundation.org>, <sam@...nborg.org>
CC:	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <linux-m32r@...linux-m32r.org>,
	<linux-m32r-ja@...linux-m32r.org>, <linux-m68k@...r.kernel.org>,
	<linux-s390@...r.kernel.org>, <sparclinux@...r.kernel.org>,
	Arpit Goel <B44344@...escale.com>
Subject: [PATCH 2/2] Convert PowerPC macro spin_event_timeout() to architecture independent macro

This patch ports PowerPC implementation of spin_event_timeout() for generic
use. Architecture specific implementation can be added to asm/delay.h, which
will override the generic linux implementation.

Signed-off-by: Arpit Goel <B44344@...escale.com>
---
 include/linux/delay.h | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/include/linux/delay.h b/include/linux/delay.h
index a6ecb34..e975994 100644
--- a/include/linux/delay.h
+++ b/include/linux/delay.h
@@ -52,4 +52,44 @@ static inline void ssleep(unsigned int seconds)
 	msleep(seconds * 1000);
 }
 
+#ifndef spin_event_timeout
+/**
+ * spin_event_timeout - spin until a condition gets true or a timeout elapses
+ * @condition: a C expression to evalate
+ * @timeout: timeout, in microseconds
+ * @delay: the number of microseconds to delay between each evaluation of
+ *         @condition
+ *
+ * The process spins until the condition evaluates to true (non-zero) or the
+ * timeout elapses.  The return value of this macro is the value of
+ * @condition when the loop terminates. This allows you to determine the cause
+ * of the loop terminates.  If the return value is zero, then you know a
+ * timeout has occurred.
+ *
+ * This primary purpose of this macro is to poll on a hardware register
+ * until a status bit changes.  The timeout ensures that the loop still
+ * terminates even if the bit never changes.  The delay is for devices that
+ * need a delay in between successive reads.
+ *
+ * gcc will optimize out the if-statement if @delay is a constant.
+ *
+ * This is copied from PowerPC based spin_event_timeout() implementation
+ * and modified for generic usecase.
+ */
+#define spin_event_timeout(condition, timeout, delay)		\
+({								\
+	typeof(condition) __ret;				\
+	unsigned long __loops = timeout/USECS_PER_JIFFY;	\
+	unsigned long __start = jiffies;			\
+	while (!(__ret = (condition)) &&			\
+		time_before(jiffies, __start + __loops + 1))	\
+		if (delay)					\
+			udelay(delay);				\
+		else						\
+			schedule();				\
+	if (!__ret)						\
+		__ret = (condition);				\
+	__ret;							\
+})
+#endif
 #endif /* defined(_LINUX_DELAY_H) */
-- 
1.8.1.4


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