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authorOleksij Rempel <linux@rempel-privat.de>2016-04-26 08:27:46 +0200
committerWolfram Sang <wsa@the-dreams.de>2016-04-26 23:34:09 +0200
commit2b899f34e1db9adef8716d07e872a800dfa60790 (patch)
tree6de5190c4e2042cf1fc4522d25f0e8398bfb0f46 /drivers/i2c
parent1bb1ff3e7c74f4569dddf7bda8054a0bb6ed0073 (diff)
downloadlinux-2b899f34e1db9adef8716d07e872a800dfa60790.tar.bz2
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.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/i2c/busses/i2c-imx.c b/drivers/i2c/busses/i2c-imx.c
index 1ca7ef2314f7..1844bc9f7cd5 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);