linux-kernel - [PATCH 1/2] time: refactor usecs_to

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Date:	Thu, 28 May 2015 19:09:55 +0200
From:	Nicholas Mc Guire <hofrat@...dl.org>
To:	Michal Marek <mmarek@...e.cz>
Cc:	Masahiro Yamada <yamada.m@...panasonic.com>,
	Sam Ravnborg <sam@...nborg.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Alvin" <hpa@...or.com>, Joe Perches <joe@...ches.com>,
	John Stultz <john.stultz@...aro.org>,
	Andrew Hunter <ahh@...gle.com>, Paul Turner <pjt@...gle.com>,
	linux-kernel@...r.kernel.org, Nicholas Mc Guire <hofrat@...dl.org>
Subject: [PATCH 1/2] time: refactor usecs_to_jiffies

Refactor the usecs_to_jiffies conditional code part in time.c and
jiffies.h putting it into conditional functions rather than #ifdefs
to improve readability. This is analogous to the msecs_to_jiffies()
cleanup commit ca42aaf0c861 ("time: Refactor msecs_to_jiffies")

Patch was build tested for:
  arm - imx_v6_v7_defconfig, vexpress_defconfig
  cris - etrax-100lx_v2_defconfig
  ia64 - generic_defconfig
  (though with lots of build warnings both with and without patch)
  m68k - multi_defconfig
  mips32 - ar7_defconfig, 
  mips64 - loongson3_defconfig 
  powerpc - 44x/virtex5_defconfig 
  powerpc64 - ppc64_defconfig
  s390 - failed to build for all defconfigs with toolchain from kernel.org
  (cc1: error: unrecognized command line option '-mtune=zEC12')
  sh - se7780_defconfig,
  sparc32 - sparc32_defconfig
  sparc64 - sparc64_defconfig
  x86 64 - x86_64_defconfig,

patch is against 4.1-rc5 (localversion-next is -next-20150527)

Link: http://lkml.org/lkml/2015/5/18/273
Signed-off-by: Nicholas Mc Guire <hofrat@...dl.org>
---

Verification of const folding
config: x86_64_defconfig + CONFIG_DRM_GMA500=m, CONFIG_DRM_GMA3600=y
drivers/gpu/drm/gma500/intel_gmbus.c
204         gpio->algo.timeout = usecs_to_jiffies(2200);                        
-> reduced to load instruction

config: x86_64_defconfig + CONFIG_INFINIBAND=m,  CONFIG_INFINIBAND_QIB=m
drivers/infiniband/hw/qib/qib_qp.c
809	qp->timeout = attr->timeout;
810	qp->timeout_jiffies =
811		usecs_to_jiffies((4096UL * (1UL << qp->timeout)) /
812			1000UL);
-> call __usecs_to_jiffies

 include/linux/jiffies.h |   27 ++++++++++++++++++++++++++-
 kernel/time/time.c      |   13 +++----------
 :2 files changed, 29 insertions(+), 11 deletions(-)

diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h
index 3bde5eb..cf6eaaf 100644
--- a/include/linux/jiffies.h
+++ b/include/linux/jiffies.h
@@ -362,7 +362,32 @@ static inline unsigned long msecs_to_jiffies(const unsigned int m)
 	}
 }
 
-extern unsigned long usecs_to_jiffies(const unsigned int u);
+extern unsigned long __usecs_to_jiffies(const unsigned int u);
+#if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
+static inline unsigned long _usecs_to_jiffies(const unsigned int u)
+{
+	return (u + (USEC_PER_SEC / HZ) - 1) / (USEC_PER_SEC / HZ);
+}
+#elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
+static inline unsigned long _usecs_to_jiffies(const unsigned int u)
+{
+	return u * (HZ / USEC_PER_SEC);
+}
+static inline unsigned long _usecs_to_jiffies(const unsigned int u)
+{
+#else
+static inline unsigned long _usecs_to_jiffies(const unsigned int u)
+{
+	return (USEC_TO_HZ_MUL32 * u + USEC_TO_HZ_ADJ32)
+		>> USEC_TO_HZ_SHR32;
+}
+#endif
+
+static inline unsigned long usecs_to_jiffies(const unsigned int u)
+{
+	return __usecs_to_jiffies(u);
+}
+
 extern unsigned long timespec_to_jiffies(const struct timespec *value);
 extern void jiffies_to_timespec(const unsigned long jiffies,
 				struct timespec *value);
diff --git a/kernel/time/time.c b/kernel/time/time.c
index 972e3bb..85d5bb1 100644
--- a/kernel/time/time.c
+++ b/kernel/time/time.c
@@ -522,20 +522,13 @@ unsigned long __msecs_to_jiffies(const unsigned int m)
 }
 EXPORT_SYMBOL(__msecs_to_jiffies);
 
-unsigned long usecs_to_jiffies(const unsigned int u)
+unsigned long __usecs_to_jiffies(const unsigned int u)
 {
 	if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET))
 		return MAX_JIFFY_OFFSET;
-#if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ)
-	return (u + (USEC_PER_SEC / HZ) - 1) / (USEC_PER_SEC / HZ);
-#elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
-	return u * (HZ / USEC_PER_SEC);
-#else
-	return (USEC_TO_HZ_MUL32 * u + USEC_TO_HZ_ADJ32)
-		>> USEC_TO_HZ_SHR32;
-#endif
+	return _usecs_to_jiffies(u);
 }
-EXPORT_SYMBOL(usecs_to_jiffies);
+EXPORT_SYMBOL(__usecs_to_jiffies);
 
 /*
  * The TICK_NSEC - 1 rounds up the value to the next resolution.  Note
-- 
1.7.10.4

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