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Mark Brown 1bc2962e53 i2c-s3c2410: Remove unconditional 1ms delay on each transfer 
The S3C I2C controller indicates completion of I2C transfers before
the bus has a stop condition on it. In order to ensure that we do not
attempt to start a new transfer before the bus is idle the driver
currently inserts a 1ms delay. This is vastly larger than is generally
required and has a visible effect on performance under load, such as
when bringing up audio CODECs or reading back status information with
non-bulk I2C reads.

Replace the sleep with a spin on the IIC status register for up to 1ms.
This will busy wait but testing on my SMDK6410 system indicates that
the overwhelming majority of transactions complete on the first spin,
with maximum latencies of less than 10 spins so the absolute overhead
of busy waiting should be at worst comprable to msleep(), and the
overall system performance is dramatically improved.

The main risk is poor interaction with multimaster systems where
we may miss the bus going idle before the next transaction. Defend
against this by falling back to the original 1ms delay after 20 spins.

The overall effect in my testing is an approximately 20% improvement
in kernel startup time.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
 		2010-05-20 00:18:58 +01:00
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accessibility
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acpi Merge branch 'x86-irq-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-05-18 09:15:57 -07:00
amba
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ata pata_pcmcia / ide-cs: Fix bad hashes for Transcend and kingston IDs 2010-05-05 14:48:48 -04:00
atm include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
auxdisplay include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
base Merge git://git.kernel.org/pub/scm/linux/kernel/git/lethal/sh-2.6 2010-05-19 11:36:03 -07:00
block Merge branch 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-05-18 08:17:35 -07:00
bluetooth include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
cdrom
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char Merge branch 'tracing-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-05-18 08:35:04 -07:00
clocksource Merge branch 'sh/stable-updates' 2010-04-26 16:08:27 +09:00
connector include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
cpufreq Merge branch 'x86-cpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-05-18 08:49:13 -07:00
cpuidle cpuidle: Fix incorrect optimization 2010-05-09 18:35:36 -07:00
crypto include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
dca include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
dio
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dma Merge git://git.kernel.org/pub/scm/linux/kernel/git/lethal/sh-2.6 2010-05-19 11:36:03 -07:00
edac edac, mce: Fix wrong mask and macro usage 2010-04-30 10:15:39 -07:00
eisa
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firewire Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux1394-2.6 2010-04-22 12:54:54 -07:00
firmware Merge branch 'x86-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/x86/linux-2.6-tip 2010-04-07 11:02:23 -07:00
gpio it8761e_gpio: fix bug in gpio numbering 2010-05-11 17:33:41 -07:00
gpu drivers/gpu/drm/i915/i915_irq.c:i915_error_object_create(): use correct kmap-atomic slot 2010-05-11 17:33:42 -07:00
hid HID: fix suspend crash by moving initializations earlier 2010-05-07 23:33:52 +02:00
hwmon Merge branch 'hwmon-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jdelvare/staging 2010-05-11 17:38:04 -07:00
i2c i2c-s3c2410: Remove unconditional 1ms delay on each transfer 2010-05-20 00:18:58 +01:00
ide pata_pcmcia / ide-cs: Fix bad hashes for Transcend and kingston IDs 2010-05-05 14:48:48 -04:00
idle include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
ieee1394 include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
ieee802154
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infiniband Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/roland/infiniband 2010-04-09 11:53:06 -07:00
input Merge branch 'for-linus/samsung4' of git://git.fluff.org/bjdooks/linux 2010-05-19 11:49:33 -07:00
isdn Fix ISDN/Gigaset build failure 2010-04-19 11:53:17 -07:00
leds include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
lguest lguest: stop using KVM hypercall mechanism 2010-04-14 21:43:56 +09:30
macintosh device_attributes: add sysfs_attr_init() for dynamic attributes 2010-04-07 08:38:03 -07:00
mca
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md md: restore ability of spare drives to spin down. 2010-05-07 21:10:57 +10:00
media V4L/DVB: pxa_camera: move fifo reset direct before dma start 2010-05-06 19:20:52 -03:00
memstick include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
message include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
mfd mfd: Clean up after WM83xx AUXADC interrupt if it arrives late 2010-05-13 12:58:55 +02:00
misc Modify the VMware balloon driver for the new x86_hyper API 2010-05-09 01:13:42 -07:00
mmc Merge branch 'devel' of master.kernel.org:/home/rmk/linux-2.6-arm 2010-05-19 11:37:22 -07:00
mtd [MTD] Remove zero-length files mtdbdi.c and internal.ho 2010-05-05 15:25:12 -04:00
net m68k: amiga - Zorro bus modalias support 2010-05-17 21:37:41 +02:00
nubus include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
of of: check for IS_ERR() 2010-04-28 01:07:29 -06:00
oprofile oprofile: protect from not being in an IRQ context 2010-05-03 23:02:39 +02:00
parisc include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
parport include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
pci Merge branch 'core-iommu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2010-05-18 07:22:37 -07:00
pcmcia [ARM] pxa: add support for Voipac PXA270 PCMCIA 2010-05-11 17:25:02 +02:00
platform eeepc-laptop: add missing sparse_keymap_free 2010-04-23 15:23:21 -04:00
pnp Merge branches 'bugzilla-14337', 'bugzilla-14998', 'bugzilla-15407', 'bugzilla-15903' and 'misc-2.6.34' into release 2010-05-06 22:04:31 -04:00
power include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
pps include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
ps3 include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
rapidio
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regulator regulator: fix enabling regulator issue on max8925 2010-04-28 15:24:34 +01:00
rtc Revert "rtc: omap: let device wakeup capability be configured from chip init logic" 2010-05-19 11:37:20 -07:00
s390 [S390] drivers/s390/char: Use kmemdup 2010-05-17 10:00:18 +02:00
sbus include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
scsi m68k: amiga - Zorro bus modalias support 2010-05-17 21:37:41 +02:00
serial Merge branch 'for-linus/samsung4' of git://git.fluff.org/bjdooks/linux 2010-05-19 11:49:33 -07:00
sfi
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sh sh: simplify WARN usage in SH clock driver 2010-05-13 17:43:11 +09:00
sn include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
spi [ARM] pxa: add namespace on ssp 2010-05-11 17:25:06 +02:00
ssb MIPS: Fix SSB PCIcore IO resource management 2010-04-12 17:26:14 +01:00
staging Merge branch 'upstream' of git://ftp.linux-mips.org/pub/scm/upstream-linus 2010-04-30 13:04:14 -07:00
tc include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
telephony
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thermal drivers/thermal/thermal_sys.c: fix 'key f70f4b50 not in .data' in thermal_sys 2010-04-07 08:38:03 -07:00
uio include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
usb Merge branch 'devel' of master.kernel.org:/home/rmk/linux-2.6-arm 2010-05-19 11:37:22 -07:00
uwb include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
vhost vhost: fix barrier pairing 2010-05-12 18:04:04 +03:00
video m68k: amiga - Frame buffer platform device conversion 2010-05-17 21:37:43 +02:00
virtio virtio: Fix GFP flags passed from the virtio balloon driver 2010-04-22 07:34:05 -07:00
vlynq include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
w1 w1: fix omap 1-wire driver compilation 2010-04-24 11:31:25 -07:00
watchdog ARM: 6126/1: ARM mpcore_wdt: fix build failure and other fixes 2010-05-12 11:18:14 +01:00
xen stop_machine: reimplement using cpu_stop 2010-05-06 18:49:20 +02:00
zorro m68k: amiga - Zorro host bridge platform device conversion 2010-05-17 21:37:42 +02:00
Kconfig
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Makefile virtio: initialize earlier 2010-05-07 14:01:17 -07:00