Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751890AbcDZMWN (ORCPT ); Tue, 26 Apr 2016 08:22:13 -0400 Received: from smtp6-v.fe.bosch.de ([139.15.237.11]:17742 "EHLO smtp6-v.fe.bosch.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751082AbcDZMWM (ORCPT ); Tue, 26 Apr 2016 08:22:12 -0400 Subject: Re: [PATCH] i2c: imx: use usleep_range(50,100) instead of udelay(50) To: Vladimir Zapolskiy , Wolfram Sang , References: <1461652066-16456-1-git-send-email-dirk.behme@de.bosch.com> <571F4AE1.7020207@mentor.com> CC: , Oleksij Rempel From: Dirk Behme Organization: Robert Bosch Car Multimedia GmbH Message-ID: <571F5D70.9010808@de.bosch.com> Date: Tue, 26 Apr 2016 14:22:08 +0200 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.7.2 MIME-Version: 1.0 In-Reply-To: <571F4AE1.7020207@mentor.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.34.217.168] X-TM-AS-MML: disable X-TM-AS-Product-Ver: IMSS-7.1.0.1679-8.0.0.1202-22284.006 X-TMASE-MatchedRID: L8tZF6zWW2oOwH4pD14DsPHkpkyUphL9suIso71Vk6KHqBkARTtlhrmi mgp+2uYCTgZkBDKEqPbTdkGRiKizr7k1SJXLdUmabc297PAGtWYFwIQBmQewZ2AMM0WKD4asKC6 fJOvu7EPIBTcJ3pjjnLvi0rANMGKQL8QeiTuGu5zpYmA4RZ8U39ZKsq3DGpalOGCgDN6EbfZTuA Q+5yzMZ04W7yyyPEbzQijPFC+6OAtQRuqW3Cd91Kt9n66zJ4RI3O6W47fn0O6bKItl61J/ycnjL TA/UDoAoTCA5Efyn8CNo+PRbWqfRK6NVEWSRWybXvYUXUJJwRUZPNmGuNWtJW8xB0EQ3YcuYPxz JtS8vCgm7aqeHKY20Zgr2094f9AGX+Yt/WWmg5gbU1VBN+1t6mB+eX8VE990hXICXPkDTMLvGya LyWJvBWLqcdF40kDywzhVZiqhieGz597RaJ+lCg== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2522 Lines: 70 On 26.04.2016 13:02, Vladimir Zapolskiy wrote: > Hi Dirk, > > On 26.04.2016 09:27, Dirk Behme wrote: >> 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 Signed-off-by: Dirk Behme > missing your Signed-off-by. > > Reviewed-by: Vladimir Zapolskiy > >> --- >> 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); >>