linux/drivers/i2c
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
..
algos Linux 3.6-rc7 2012-10-08 12:46:32 +02:00
busses i2c: s3c2410: use exponential back off while polling for bus idle 2012-11-16 13:09:33 +01:00
muxes i2c: mux: Add dt support to i2c-mux-gpio driver 2012-11-16 09:28:27 +01:00
i2c-boardinfo.c i2c: Update the FSF address 2012-03-26 21:47:19 +02:00
i2c-core.c i2c: Convert struct i2c_msg initialization to C99 format 2012-10-05 22:23:52 +02:00
i2c-core.h i2c: Update the FSF address 2012-03-26 21:47:19 +02:00
i2c-dev.c i2c-dev: Add support for I2C_M_RECV_LEN 2012-05-30 10:55:34 +02:00
i2c-mux.c i2c-mux: Add support for device auto-detection 2012-10-05 22:23:51 +02:00
i2c-smbus.c i2c-smbus: Convert kzalloc to devm_kzalloc 2012-10-05 22:23:52 +02:00
i2c-stub.c i2c-stub: Move to drivers/i2c 2012-10-28 21:37:00 +01:00
Kconfig i2c: Make I2C available on UML 2012-10-05 22:23:52 +02:00
Makefile i2c-stub: Move to drivers/i2c 2012-10-28 21:37:00 +01:00