i2c: imx: reduce load by using usleep_range instead of udelay
Documentation/timers/timers-howto.txt recommends to use
usleep_range on delays > 10usec. According to my test results
with Neonode zForce touchscreen driver, usleep_range indeed
reduces CPU load.
Stats collected with "./perf record -a -g -F 1000 sleep 10"
i2c-imx with udelay(50):
34.19% 0.00% irq/220-Neonode [kernel.kallsyms] [k] irq_thread
---irq_thread
|--33.75%--irq_thread_fn
| |--19.27%--0x7f08a878
| | i2c_master_recv
| | i2c_transfer
| | __i2c_transfer
| | i2c_imx_xfer
| | |--11.71%--i2c_imx_trx_complete
| | |--5.70%--i2c_imx_start <<<<----------------
| | | |--5.38%--__timer_const_udelay
| | | | __timer_delay
| | | | --5.07%--read_current_timer
i2c-imx with usleep_range(50,100)
29.08% 0.00% irq/220-Neonode [kernel.kallsyms] [k] irq_thread
---irq_thread
|--28.89%--irq_thread_fn
| |--17.21%--0x7f08a878
| | i2c_master_recv
| | |--17.14%--i2c_transfer
| | | __i2c_transfer
| | | i2c_imx_xfer
| | | |--14.29%--i2c_imx_trx_complete
| | | |--1.42%--i2c_imx_start <<<<----------
| | | | |--0.71%--usleep_range
| | | | |--0.53%--i2c_imx_bus_busy
Signed-off-by: Oleksij Rempel <linux@rempel-privat.de>
Signed-off-by: Dirk Behme <dirk.behme@de.bosch.com>
Reviewed-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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