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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
..
Kconfig ARM: Add Versatile Express support 2010-05-02 09:35:38 +01:00
Makefile i2c: Add support for Xilinx XPS IIC Bus Interface 2010-03-07 22:28:39 +00:00
i2c-acorn.c [ARM] acorn,ebsa110,footbridge,integrator,sa1100: Convert asm/io.h to linux/io.h 2009-03-25 10:21:35 +00:00
i2c-ali15x3.c i2c: Make PCI device ids constant 2010-03-02 12:23:37 +01:00
i2c-ali1535.c i2c: Make PCI device ids constant 2010-03-02 12:23:37 +01:00
i2c-ali1563.c i2c: Make PCI device ids constant 2010-03-02 12:23:37 +01:00
i2c-amd756-s4882.c i2c: Use snprintf to set adapter names 2009-01-07 14:29:18 +01:00
i2c-amd756.c i2c: Make PCI device ids constant 2010-03-02 12:23:37 +01:00
i2c-amd8111.c 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
i2c-at91.c i2c: Use resource_size macro 2009-06-16 22:42:16 +01:00
i2c-au1550.c i2c: Use resource_size macro 2009-06-16 22:42:16 +01:00
i2c-bfin-twi.c 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
i2c-cpm.c i2c: Fix stuck transaction on cpm-i2c driver 2009-06-22 01:43:32 +01:00
i2c-davinci.c 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
i2c-designware.c 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
i2c-elektor.c 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
i2c-gpio.c 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
i2c-highlander.c 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
i2c-hydra.c i2c: Make PCI device ids constant 2010-03-02 12:23:37 +01:00
i2c-i801.c i2c-i801: Don't use the block buffer for I2C block writes 2010-03-13 20:56:53 +01:00
i2c-ibm_iic.c Remove multiple KERN_ prefixes from printk formats 2009-07-08 10:30:03 -07:00
i2c-ibm_iic.h i2c-ibm_iic: Whitespace cleanup 2008-01-27 18:14:45 +01:00
i2c-imx.c i2c-imx: fix error handling 2010-04-20 01:16:57 +01:00
i2c-iop3xx.c i2c: Bus drivers don't have to support I2C_M_REV_DIR_ADDR 2009-12-06 17:06:22 +01:00
i2c-iop3xx.h [PATCH] i2c-iop3xx: Avoid addressing self 2006-07-12 15:43:06 -07:00
i2c-isch.c i2c: convert i2c-isch to platform_device 2010-03-07 22:17:36 +01:00
i2c-ixp2000.c 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
i2c-mpc.c 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
i2c-mv64xxx.c 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
i2c-nforce2-s4985.c i2c: Fix oops on bus multiplexer driver loading 2008-08-10 22:56:15 +02:00
i2c-nforce2.c 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
i2c-nomadik.c 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
i2c-ocores.c 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
i2c-octeon.c I2C: Fix section mismatch errors in i2c-octeon.c 2010-04-30 20:52:52 +01:00
i2c-omap.c i2c-omap: fix OOPS in omap_i2c_unidle() during probe 2010-04-20 01:16:57 +01:00
i2c-parport-light.c i2c-parport-light: Add SMBus alert support 2010-03-02 12:23:45 +01:00
i2c-parport.c 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
i2c-parport.h i2c-parport: Add SMBus alert support 2010-03-02 12:23:44 +01:00
i2c-pasemi.c 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
i2c-pca-isa.c i2c/pca: Don't use *_interruptible 2010-01-16 20:43:13 +01:00
i2c-pca-platform.c i2c/pca: Don't use *_interruptible 2010-01-16 20:43:13 +01:00
i2c-piix4.c i2c: Make PCI device ids constant 2010-03-02 12:23:37 +01:00
i2c-pmcmsp.c i2c: Use resource_size macro 2009-06-16 22:42:16 +01:00
i2c-pnx.c i2c-pnx: Add stop conditions for end of transfer 2010-04-20 01:16:57 +01:00
i2c-powermac.c i2c-powermac: Be less verbose in the absence of real errors. 2010-03-13 20:56:52 +01:00
i2c-pxa.c 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
i2c-s3c2410.c i2c-s3c2410: Remove unconditional 1ms delay on each transfer 2010-05-20 00:18:58 +01:00
i2c-s6000.c i2c: xtensa s6000 i2c driver 2009-04-07 10:23:34 +01:00
i2c-s6000.h i2c: xtensa s6000 i2c driver 2009-04-07 10:23:34 +01:00
i2c-scmi.c i2c-scmi: Provide module aliases for automatic loading 2010-03-24 14:38:39 +01:00
i2c-sh7760.c sh: clkfwk: module_clk -> peripheral_clk rename. 2009-05-13 16:59:40 +09:00
i2c-sh_mobile.c 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
i2c-sibyte.c i2c: Delete many unused adapter IDs 2009-01-26 21:19:52 +01:00
i2c-simtec.c 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
i2c-sis96x.c i2c: Make PCI device ids constant 2010-03-02 12:23:37 +01:00
i2c-sis630.c i2c: Make PCI device ids constant 2010-03-02 12:23:37 +01:00
i2c-sis5595.c i2c: Make PCI device ids constant 2010-03-02 12:23:37 +01:00
i2c-stu300.c i2c-stu300: off by one issue 2010-04-20 01:17:13 +01:00
i2c-stub.c i2c-stub: Allow user to disable some commands 2009-12-06 17:06:29 +01:00
i2c-taos-evm.c i2c-taos-evm: Switch echo off to improve performance 2009-09-18 22:45:43 +02:00
i2c-tiny-usb.c 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
i2c-versatile.c 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
i2c-via.c i2c: Make PCI device ids constant 2010-03-02 12:23:37 +01:00
i2c-viapro.c i2c: Make PCI device ids constant 2010-03-02 12:23:37 +01:00
i2c-xiic.c 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
scx200_acb.c 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
scx200_i2c.c i2c: Make sure i2c_algo_bit_data.timeout is HZ-independent 2009-02-24 19:19:49 +01:00