Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756040Ab2EJGTx (ORCPT ); Thu, 10 May 2012 02:19:53 -0400 Received: from na3sys009aog130.obsmtp.com ([74.125.149.143]:48851 "EHLO na3sys009aog130.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754560Ab2EJGTs convert rfc822-to-8bit (ORCPT ); Thu, 10 May 2012 02:19:48 -0400 MIME-Version: 1.0 In-Reply-To: <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> <331ABD5ECB02734CA317220B2BBEABC13E9B667C@DBDE01.ent.ti.com> Date: Thu, 10 May 2012 11:49:47 +0530 Message-ID: Subject: Re: [PATCH V3 05/10] ARM: OMAP2+: SmartReflex: introduce a busy loop condition test macro From: "J, KEERTHY" To: "AnilKumar, Chimata" 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" Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4890 Lines: 118 On Tue, May 8, 2012 at 3:47 PM, AnilKumar, Chimata wrote: > 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 Thanks. My bad. I meant yielding to another thread with in a space of 1uS. > > Regards > AnilKumar > -- Regards and Thanks, Keerthy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/