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Date: Tue, 26 Apr 2016 14:22:08 +0200 From: Dirk Behme <dirk.behme@...bosch.com> To: Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>, Wolfram Sang <wsa@...-dreams.de>, <linux-i2c@...r.kernel.org> CC: <linux-kernel@...r.kernel.org>, Oleksij Rempel <linux@...pel-privat.de> Subject: Re: [PATCH] i2c: imx: use usleep_range(50,100) instead of udelay(50) On 26.04.2016 13:02, Vladimir Zapolskiy wrote: > Hi Dirk, > > On 26.04.2016 09:27, Dirk Behme wrote: >> From: Oleksij Rempel <linux@...pel-privat.de> >> >> 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@...pel-privat.de> Signed-off-by: Dirk Behme <dirk.behme@...bosch.com> > missing your Signed-off-by. > > Reviewed-by: Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com> > >> --- >> 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); >>
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