1bc2962e53
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> |
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| .. | ||
| algos | ||
| busses | ||
| Kconfig | ||
| Makefile | ||
| i2c-boardinfo.c | ||
| i2c-core.c | ||
| i2c-core.h | ||
| i2c-dev.c | ||
| i2c-smbus.c | ||