Hi Dirk, On 26.04.2016 09:27, Dirk Behme wrote: > From: Oleksij Rempel <linux@xxxxxxxxxxxxxxxx> > > 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@xxxxxxxxxxxxxxxx> missing your Signed-off-by. Reviewed-by: Vladimir Zapolskiy <vladimir_zapolskiy@xxxxxxxxxx> > --- > drivers/i2c/busses/i2c-imx.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > 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); > -- With best wishes, Vladimir -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
