Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752212AbcDZG1x (ORCPT ); Tue, 26 Apr 2016 02:27:53 -0400 Received: from smtp6-v.fe.bosch.de ([139.15.237.11]:60293 "EHLO smtp6-v.fe.bosch.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750995AbcDZG1w (ORCPT ); Tue, 26 Apr 2016 02:27:52 -0400 From: Dirk Behme To: Wolfram Sang , CC: , Oleksij Rempel Subject: [PATCH] i2c: imx: use usleep_range(50,100) instead of udelay(50) Date: Tue, 26 Apr 2016 08:27:46 +0200 Message-ID: <1461652066-16456-1-git-send-email-dirk.behme@de.bosch.com> X-Mailer: git-send-email 2.8.0 MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-MML: disable X-TM-AS-Product-Ver: IMSS-7.1.0.1679-8.0.0.1202-22282.006 X-TMASE-MatchedRID: YYyDZv203eUbPfD7r6VrxTbbKRaLVs/8UAjrAJWsTe9h7WbOnt2TB71l PScvuQ2v8UwcoTZR9Q2z9iIN/2YQzSS9ZxL039YHGVyS87Wb4lxlMi611URCVfA0wiLIxfVXrc3 G1j5u/Gr9EXmd1GRSytsIe/TXUbL1kKjL2IOi2LDd+fuf9kcappPsKtZChJUlhYk/dd0YDC5jdq mz8n0u+uLzNWBegCW2Nfpe10T3IsMLbigRnpKlKZx+7GyJjhAU+qKa0iVHR8LWBxhybp8pVg/Dw rj/u8m1p7GrjqynsS3KFJbiv3N04HdkWjDAQ7wtpShLmXToajY+PR/6JcSqTpgaBT6IuxZdh/iX dbS1V7u7j2rWxYQLt0cGnllPWffhN10+4fC3tMDFhXMjdQIJpg== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2085 Lines: 58 From: Oleksij Rempel 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 --- 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