From 2b899f34e1db9adef8716d07e872a800dfa60790 Mon Sep 17 00:00:00 2001 From: Oleksij Rempel Date: Tue, 26 Apr 2016 08:27:46 +0200 Subject: 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 Signed-off-by: Dirk Behme Reviewed-by: Vladimir Zapolskiy Signed-off-by: Wolfram Sang --- drivers/i2c/busses/i2c-imx.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/i2c') 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); -- cgit v1.2.3-55-g7522