From: Dirk Behme <dirk.behme@de.bosch.com>
To: Wolfram Sang <wsa@the-dreams.de>, linux-i2c@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, Oleksij Rempel <linux@rempel-privat.de>
Subject: [PATCH] i2c: imx: use usleep_range(50,100) instead of udelay(50)
Date: Tue, 26 Apr 2016 08:27:46 +0200 [thread overview]
Message-ID: <1461652066-16456-1-git-send-email-dirk.behme@de.bosch.com> (raw)
From: Oleksij Rempel <linux@rempel-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@rempel-privat.de>
---
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);
--
2.8.0
next reply other threads:[~2016-04-26 6:27 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-26 6:27 Dirk Behme [this message]
2016-04-26 11:02 ` [PATCH] i2c: imx: use usleep_range(50,100) instead of udelay(50) Vladimir Zapolskiy
2016-04-26 12:22 ` Dirk Behme
2016-04-26 21:35 ` Wolfram Sang
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