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| author | Oleksij Rempel <linux@rempel-privat.de> | 2016-04-26 06:27:46 (GMT) |
|---|---|---|
| committer | Wolfram Sang <wsa@the-dreams.de> | 2016-04-26 21:34:09 (GMT) |
| commit | 2b899f34e1db9adef8716d07e872a800dfa60790 (patch) | |
| tree | 6de5190c4e2042cf1fc4522d25f0e8398bfb0f46 /drivers/i2c | |
| parent | 1bb1ff3e7c74f4569dddf7bda8054a0bb6ed0073 (diff) | |
| download | linux-2b899f34e1db9adef8716d07e872a800dfa60790.tar.xz | |
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>
Diffstat (limited to 'drivers/i2c')
| -rw-r--r-- | drivers/i2c/busses/i2c-imx.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c index 1ca7ef2..1844bc9 100644 --- a/drivers/i2c/busses/i2c-imx.c +++ b/drivers/i2c/busses/i2c-imx.c @@ -525,7 +525,7 @@ static int i2c_imx_start(struct imx_i2c_struct *i2c_imx) imx_i2c_write_reg(i2c_imx->hwdata->i2cr_ien_opcode, i2c_imx, IMX_I2C_I2CR); /* Wait controller to be stable */ - udelay(50); + usleep_range(50, 150); /* Start I2C transaction */ temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR); |