From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753221Ab2EHKR5 (ORCPT ); Tue, 8 May 2012 06:17:57 -0400 Received: from bear.ext.ti.com ([192.94.94.41]:49402 "EHLO bear.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752851Ab2EHKRz convert rfc822-to-8bit (ORCPT ); Tue, 8 May 2012 06:17:55 -0400 From: "AnilKumar, Chimata" To: "J, KEERTHY" CC: "linux-omap@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "Hilman, Kevin" , "rjw@sisk.pl" , "linux-kernel@vger.kernel.org" , "linux-pm@lists.linux-foundation.org" , "Pihet-XID, Jean" Subject: RE: [PATCH V3 05/10] ARM: OMAP2+: SmartReflex: introduce a busy loop condition test macro Thread-Topic: [PATCH V3 05/10] ARM: OMAP2+: SmartReflex: introduce a busy loop condition test macro Thread-Index: AQHNI9QqacStCvxp2EqO7BVNbqIaSpa5YatQgAQdGYCAAkDsIA== Date: Tue, 8 May 2012 10:17:41 +0000 Message-ID: <331ABD5ECB02734CA317220B2BBEABC13E9B667C@DBDE01.ent.ti.com> References: <1335462041-4949-1-git-send-email-j-keerthy@ti.com> <1335462041-4949-6-git-send-email-j-keerthy@ti.com> <331ABD5ECB02734CA317220B2BBEABC13E9B1B40@DBDE01.ent.ti.com> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [172.24.133.24] Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 07, 2012 at 10:51:53, J, KEERTHY wrote: > On Fri, May 4, 2012 at 2:42 PM, AnilKumar, Chimata wrote: > > On Thu, Apr 26, 2012 at 23:10:36, J, KEERTHY wrote: > >> From: Jean Pihet > >> > >> Now that omap_test_timeout is only accessible from mach-omap2/, > >> introduce a similar function for SR. > >> > >> This change makes the SmartReflex implementation ready for the move > >> to drivers/. > >> > >> Signed-off-by: Jean Pihet > >> Signed-off-by: J Keerthy > >> --- > >>  arch/arm/mach-omap2/smartreflex.c |   12 ++++++------ > >>  include/linux/power/smartreflex.h |   23 ++++++++++++++++++++++- > >>  2 files changed, 28 insertions(+), 7 deletions(-) > >> > >> diff --git a/arch/arm/mach-omap2/smartreflex.c b/arch/arm/mach-omap2/smartreflex.c > >> index d859277..acef08d 100644 > >> --- a/arch/arm/mach-omap2/smartreflex.c > >> +++ b/arch/arm/mach-omap2/smartreflex.c > >> @@ -289,9 +289,9 @@ static void sr_v1_disable(struct omap_sr *sr) > >>        * Wait for SR to be disabled. > >>        * wait until ERRCONFIG.MCUDISACKINTST = 1. Typical latency is 1us. > >>        */ > >> -     omap_test_timeout((sr_read_reg(sr, ERRCONFIG_V1) & > >> -                     ERRCONFIG_MCUDISACKINTST), SR_DISABLE_TIMEOUT, > >> -                     timeout); > >> +     sr_test_cond_timeout((sr_read_reg(sr, ERRCONFIG_V1) & > >> +                          ERRCONFIG_MCUDISACKINTST), SR_DISABLE_TIMEOUT, > >> +                          timeout); > >> > >>       if (timeout >= SR_DISABLE_TIMEOUT) > >>               dev_warn(&sr->pdev->dev, "%s: Smartreflex disable timedout\n", > >> @@ -334,9 +334,9 @@ static void sr_v2_disable(struct omap_sr *sr) > >>        * Wait for SR to be disabled. > >>        * wait until IRQSTATUS.MCUDISACKINTST = 1. Typical latency is 1us. > >>        */ > >> -     omap_test_timeout((sr_read_reg(sr, IRQSTATUS) & > >> -                     IRQSTATUS_MCUDISABLEACKINT), SR_DISABLE_TIMEOUT, > >> -                     timeout); > >> +     sr_test_cond_timeout((sr_read_reg(sr, IRQSTATUS) & > >> +                          IRQSTATUS_MCUDISABLEACKINT), SR_DISABLE_TIMEOUT, > >> +                          timeout); > >> > >>       if (timeout >= SR_DISABLE_TIMEOUT) > >>               dev_warn(&sr->pdev->dev, "%s: Smartreflex disable timedout\n", > >> diff --git a/include/linux/power/smartreflex.h b/include/linux/power/smartreflex.h > >> index 884eaee..78b795e 100644 > >> --- a/include/linux/power/smartreflex.h > >> +++ b/include/linux/power/smartreflex.h > >> @@ -22,7 +22,7 @@ > >> > >>  #include > >>  #include > >> - > >> +#include > >>  #include > >> > >>  /* > >> @@ -168,6 +168,27 @@ struct omap_sr { > >>  }; > >> > >>  /** > >> + * test_cond_timeout - busy-loop, testing a condition > >> + * @cond: condition to test until it evaluates to true > >> + * @timeout: maximum number of microseconds in the timeout > >> + * @index: loop index (integer) > >> + * > >> + * Loop waiting for @cond to become true or until at least @timeout > >> + * microseconds have passed.  To use, define some integer @index in the > >> + * calling code.  After running, if @index == @timeout, then the loop has > >> + * timed out. > >> + * > >> + * Copied from omap_test_timeout */ > >> +#define sr_test_cond_timeout(cond, timeout, index)           \ > >> +({                                                           \ > >> +     for (index = 0; index < timeout; index++) {             \ > >> +             if (cond)                                       \ > >> +                     break;                                  \ > >> +             udelay(1);                                      \ > >> +     }                                                       \ > >> +}) > > > > I think we can use time_after()/time_before() APIs for timeout and cpu_relax() for > > tight loops instead of udelay(). > > cpu_relax() changes the priority everytime to low and will yield to > another thread. > Considering that we are checking the condition every microsecond does it make > some saving using cpu_relax(). > cpu_relax() does not involve any priority changes or scheduling AFAICS. Have a look at this thread: http://www.spinics.net/lists/netdev/msg151699.html Regards AnilKumar