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fe724bf9f0
linux/drivers/i2c/busses
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Daniel Kurtz fe724bf9f0 i2c: s3c2410: use exponential back off while polling for bus idle 
Usually, the i2c controller has finished emitting the i2c STOP before the
driver reaches the bus idle polling loop.  Optimize for this most common
case by reading IICSTAT first and potentially skipping the loop.

If the cpu is faster than the hardware, we wait for bus idle in a polling
loop.  However, since the duration of one iteration of the loop is
dependent on cpu freq, and this i2c IP is used on many different systems,
use a time based loop timeout (5 ms).

We would like very low latencies to detect bus idle for the normal
'fast' case.  However, if a device is slow to release the bus for some
reason, it could hold off the STOP generation for up to several
milliseconds.  Rapidly polling for bus idle would seriously load the CPU
while waiting for it to release the bus.  So, use a partial exponential
backoff as a compromise between idle detection latency and cpu load.

Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
Signed-off-by: Naveen Krishna Chatradhi <ch.naveen@samsung.com>
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
2012-11-16 13:09:33 +01:00
..
i2c-acorn.c Remove all #inclusions of asm/system.h 2012-03-28 18:30:03 +01:00
i2c-ali15x3.c i2c/busses: Use module_pci_driver 2012-07-24 14:13:56 +02:00
i2c-ali1535.c i2c/busses: Use module_pci_driver 2012-07-24 14:13:56 +02:00
i2c-ali1563.c i2c/busses: Use module_pci_driver 2012-07-24 14:13:56 +02:00
i2c-amd756-s4882.c
i2c-amd756.c i2c/busses: Use module_pci_driver 2012-07-24 14:13:56 +02:00
i2c-amd8111.c i2c/busses: Use module_pci_driver 2012-07-24 14:13:56 +02:00
i2c-at91.c i2c: at91: fix SMBus quick command 2012-11-14 10:28:28 +01:00
i2c-au1550.c i2c/busses: Use module_platform_driver() 2012-01-12 20:32:04 +01:00
i2c-bfin-twi.c i2c: i2c-bfin-twi: Move blackfin TWI register access Macro to head file. 2012-07-13 08:37:31 +02:00
i2c-cpm.c i2c/busses: Use module_platform_driver() 2012-01-12 20:32:04 +01:00
i2c-davinci.c Merge branch 'i2c-embedded/for-next' of git://git.pengutronix.de/git/wsa/linux 2012-10-11 10:27:51 +09:00
i2c-designware-core.c i2c-designware: i2c_dw_xfer_msg can be static 2012-10-05 22:23:53 +02:00
i2c-designware-core.h i2c: designware: Add support for 16bit register access 2012-05-12 14:28:11 +02:00
i2c-designware-pcidrv.c i2c/busses: Use module_pci_driver 2012-07-24 14:13:56 +02:00
i2c-designware-platdrv.c i2c: designware: Add clk_{un}prepare() support 2012-05-12 14:28:15 +02:00
i2c-diolan-u2c.c i2c: diolan-u2c: Fix master_xfer return code 2012-08-18 12:27:27 +02:00
i2c-eg20t.c i2c/busses: Use module_pci_driver 2012-07-24 14:13:56 +02:00
i2c-elektor.c
i2c-gpio.c i2c: i2c-gpio: fix name issue with multiple i2c gpio nodes 2012-11-14 09:56:43 +01:00
i2c-highlander.c Autogenerated GPG tag for Rusty D1ADB8F1: 15EE 8D6C AB0E 7F0C F999 BFCB D920 0E6C D1AD B8F1 2012-01-14 12:32:16 -08:00
i2c-hydra.c i2c/busses: Use module_pci_driver 2012-07-24 14:13:56 +02:00
i2c-i801.c i2c-i801: Fix comment 2012-10-28 21:37:01 +01:00
i2c-ibm_iic.c Autogenerated GPG tag for Rusty D1ADB8F1: 15EE 8D6C AB0E 7F0C F999 BFCB D920 0E6C D1AD B8F1 2012-01-14 12:32:16 -08:00
i2c-ibm_iic.h
i2c-imx.c Merge branch 'i2c-embedded/for-next' of git://git.pengutronix.de/git/wsa/linux 2012-10-11 10:27:51 +09:00
i2c-intel-mid.c i2c/busses: Use module_pci_driver 2012-07-24 14:13:56 +02:00
i2c-iop3xx.c i2c: iop3xx: use standard gpiolib functions 2012-07-25 09:26:41 -05:00
i2c-iop3xx.h
i2c-isch.c i2c-isch: Decrease delay in command completion check loop 2012-03-26 21:47:18 +02:00
i2c-mpc.c Merge branch 'i2c-embedded/for-next' of git://git.pengutronix.de/git/wsa/linux 2012-10-11 10:27:51 +09:00
i2c-mv64xxx.c I2C: MV64XYZ: Add Device Tree support 2012-07-23 22:04:11 +02:00
i2c-mxs.c i2c: mxs: remove broken PIOQUEUE support 2012-11-02 10:52:32 +01:00
i2c-nforce2-s4985.c
i2c-nforce2.c i2c/busses: Use module_pci_driver 2012-07-24 14:13:56 +02:00
i2c-nomadik.c i2c: nomadik: Fix the usage of wait_for_completion_timeout 2012-11-12 18:21:55 +01:00
i2c-nuc900.c ARM: w90x900: move platform_data definitions 2012-09-14 11:18:59 +02:00
i2c-ocores.c i2c: ocores: Use devm_request_and_ioremap() 2012-11-13 12:16:24 +01:00
i2c-octeon.c i2c: Convert i2c-octeon.c to use device tree. 2012-07-23 13:54:53 +01:00
i2c-omap.c i2c: omap: don't save a value only needed for read-clearing 2012-11-14 19:52:12 +01:00
i2c-parport-light.c
i2c-parport.c i2c-parport: i2c_parport_irq can be static 2012-10-05 22:23:53 +02:00
i2c-parport.h
i2c-pasemi.c i2c/busses: Use module_pci_driver 2012-07-24 14:13:56 +02:00
i2c-pca-isa.c
i2c-pca-platform.c i2c: Dynamically assign adapter id if it wasn't explictly specified 2012-05-12 14:28:11 +02:00
i2c-piix4.c i2c-piix4: Fix build failure 2012-10-05 22:23:55 +02:00
i2c-pmcmsp.c i2c-pmcmsp: remove IRQF_SAMPLE_RANDOM which is now a no-op 2012-07-19 10:38:47 -04:00
i2c-pnx.c i2c: pnx: Fix read transactions of >= 2 bytes 2012-09-12 17:52:44 +02:00
i2c-powermac.c i2c/powermac: Improve detection of devices from device-tree 2012-07-11 18:22:46 +10:00
i2c-puv3.c i2c-puv3: Use struct dev_pm_ops for power management 2012-07-12 12:04:54 +02:00
i2c-pxa-pci.c i2c/busses: Use module_pci_driver 2012-07-24 14:13:56 +02:00
i2c-pxa.c i2c/i2c-pxa: remove conditional compilation of clk code 2012-07-30 17:25:12 -07:00
i2c-rcar.c i2c: rcar: fix section mismatch 2012-11-13 11:24:15 +01:00
i2c-s3c2410.c i2c: s3c2410: use exponential back off while polling for bus idle 2012-11-16 13:09:33 +01:00
i2c-s6000.c i2c: Change mail address of Oskar Schirmer 2012-05-17 15:15:56 +02:00
i2c-s6000.h i2c: Change mail address of Oskar Schirmer 2012-05-17 15:15:56 +02:00
i2c-scmi.c i2c-scmi: convert to module_acpi_driver() 2012-09-21 13:39:56 -04:00
i2c-sh7760.c i2c/busses: Use module_platform_driver() 2012-01-12 20:32:04 +01:00
i2c-sh_mobile.c i2c: i2c-sh_mobile: fix spurious transfer request timed out 2012-11-16 09:09:13 +01:00
i2c-sibyte.c
i2c-simtec.c i2c/busses: Use module_platform_driver() 2012-01-12 20:32:04 +01:00
i2c-sirf.c i2c: add CSR SiRFprimaII on-chip I2C controllers driver 2012-03-07 19:05:04 +01:00
i2c-sis96x.c i2c/busses: Use module_pci_driver 2012-07-24 14:13:56 +02:00
i2c-sis630.c i2c/busses: Use module_pci_driver 2012-07-24 14:13:56 +02:00
i2c-sis5595.c i2c: Convert to DEFINE_PCI_DEVICE_TABLE 2012-01-12 20:32:04 +01:00
i2c-stu300.c i2c: stu300: use devm managed resources 2012-07-16 13:48:51 +02:00
i2c-taos-evm.c
i2c-tegra.c i2c: tegra: set irq name as device name 2012-11-02 10:52:52 +01:00
i2c-tiny-usb.c i2c-tiny-usb: Add support for the Robofuzz OSIF USB/I2C converter 2012-07-24 14:13:59 +02:00
i2c-versatile.c i2c: Dynamically assign adapter id if it wasn't explictly specified 2012-05-12 14:28:11 +02:00
i2c-via.c i2c/busses: Use module_pci_driver 2012-07-24 14:13:56 +02:00
i2c-viapro.c i2c-viapro: Add VIA VX900 device ID 2012-10-05 22:23:53 +02:00
i2c-xiic.c I2C: xiic: Add OF binding support 2012-05-12 14:28:18 +02:00
i2c-xlr.c i2c: Support for Netlogic XLR/XLS I2C controller. 2012-02-24 22:25:57 +01:00
Kconfig i2c-i801: Simplify dependency towards GPIOLIB 2012-10-28 21:37:01 +01:00
Makefile i2c-stub: Move to drivers/i2c 2012-10-28 21:37:00 +01:00
scx200_acb.c i2c/scx200_*: Replace printks with pr_<level>s 2012-10-05 22:23:52 +02:00
scx200_i2c.c i2c/scx200_*: Replace printks with pr_<level>s 2012-10-05 22:23:52 +02:00