From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753797AbcHPOAA (ORCPT ); Tue, 16 Aug 2016 10:00:00 -0400 Received: from mga09.intel.com ([134.134.136.24]:55753 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752434AbcHPN77 (ORCPT ); Tue, 16 Aug 2016 09:59:59 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.28,529,1464678000"; d="scan'208";a="156561423" Subject: Re: [PATCH v3 1/3] i2c: designware: wait for disable/enable only if necessary To: Lucas De Marchi , linux-i2c@vger.kernel.org References: <1469743424-2480-1-git-send-email-lucas.demarchi@intel.com> <1469743424-2480-2-git-send-email-lucas.demarchi@intel.com> Cc: christian.ruppert@alitech.com, linux-kernel@vger.kernel.org, mika.westerberg@linux.intel.com, =?UTF-8?Q?Jos=c3=a9_Roberto_de_Souza?= , Wolfram Sang From: Jarkko Nikula Message-ID: Date: Tue, 16 Aug 2016 16:59:55 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Icedove/45.2.0 MIME-Version: 1.0 In-Reply-To: <1469743424-2480-2-git-send-email-lucas.demarchi@intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, + Wolfram On 07/29/2016 01:03 AM, Lucas De Marchi wrote: > From: José Roberto de Souza > > If we aren't going to continue using the controller we can just disable > it instead of waiting for it to complete. The biggest improvement here > is when a I2C transaction is completed and it doesn't block until > the adapter is disabled. When a new transfer is needed we will disable > and wait for its completion. > > This way the adapter will continue changing its state in parallel to the > execution of the thread that requested the I2C transaction saving most > of the time 25~250 usec per I2C transaction. > > A simple program doing a register read (1 byte write, 1 byte read) > alternating on 2 different slaves repeated 25k times for each and > measurements taken 4 times we get: > > perf stat -r4 chrt -f 10 ./i2c-test /dev/i2c-1 25000 0x40 0x6 0x1e 0x00 > > Before: > 30.879317977 seconds time elapsed ( +- 14.83% ) > After: > 8.638705161 seconds time elapsed ( +- 5.90% ) > > Signed-off-by: José Roberto de Souza > Signed-off-by: Lucas De Marchi > --- > drivers/i2c/busses/i2c-designware-core.c | 13 +++++++++---- > 1 file changed, 9 insertions(+), 4 deletions(-) > Acked-by: Jarkko Nikula