From patchwork Wed Oct 17 20:12:22 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Hunter, Jon" X-Patchwork-Id: 1607741 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-process-083081@patchwork1.kernel.org Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) by patchwork1.kernel.org (Postfix) with ESMTP id CC43E3FE36 for ; Wed, 17 Oct 2012 20:14:31 +0000 (UTC) Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.76 #1 (Red Hat Linux)) id 1TOZyi-0007Tc-0T; Wed, 17 Oct 2012 20:12:32 +0000 Received: from bear.ext.ti.com ([192.94.94.41]) by merlin.infradead.org with esmtps (Exim 4.76 #1 (Red Hat Linux)) id 1TOZye-0007TP-7U for linux-arm-kernel@lists.infradead.org; Wed, 17 Oct 2012 20:12:29 +0000 Received: from dlelxv30.itg.ti.com ([172.17.2.17]) by bear.ext.ti.com (8.13.7/8.13.7) with ESMTP id q9HKCPSp001505; Wed, 17 Oct 2012 15:12:25 -0500 Received: from DFLE73.ent.ti.com (dfle73.ent.ti.com [128.247.5.110]) by dlelxv30.itg.ti.com (8.13.8/8.13.8) with ESMTP id q9HKCP9S015141; Wed, 17 Oct 2012 15:12:25 -0500 Received: from dlelxv23.itg.ti.com (172.17.1.198) by dfle73.ent.ti.com (128.247.5.110) with Microsoft SMTP Server id 14.1.323.3; Wed, 17 Oct 2012 15:12:25 -0500 Received: from legion.dal.design.ti.com (legion.dal.design.ti.com [128.247.22.53]) by dlelxv23.itg.ti.com (8.13.8/8.13.8) with ESMTP id q9HKCP5x012087; Wed, 17 Oct 2012 15:12:25 -0500 Received: from localhost (h112-54.vpn.ti.com [172.24.112.54]) by legion.dal.design.ti.com (8.11.7p1+Sun/8.11.7) with ESMTP id q9HKCPw20988; Wed, 17 Oct 2012 15:12:25 -0500 (CDT) From: Jon Hunter To: Paul Walmsley , Benoit Cousson , Kevin Hilman Subject: [PATCH] ARM: OMAP2+: Only write the sysconfig on idle when necessary Date: Wed, 17 Oct 2012 15:12:22 -0500 Message-ID: <1350504742-19995-1-git-send-email-jon-hunter@ti.com> X-Mailer: git-send-email 1.7.9.5 MIME-Version: 1.0 X-Spam-Note: CRM114 invocation failed X-Spam-Score: -7.3 (-------) X-Spam-Report: SpamAssassin version 3.3.2 on merlin.infradead.org summary: Content analysis details: (-7.3 points) pts rule name description ---- ---------------------- -------------------------------------------------- -5.0 RCVD_IN_DNSWL_HI RBL: Sender listed at http://www.dnswl.org/, high trust [192.94.94.41 listed in list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record -0.4 RP_MATCHES_RCVD Envelope sender domain matches handover relay domain -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] Cc: linux-omap , Jon Hunter , linux-arm X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-arm-kernel-bounces@lists.infradead.org Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org Currently, whenever we idle a device _idle_sysc() is called and writes to the devices SYSCONFIG register to set the idle mode. A lot devices are using the smart-idle mode and so the write to the SYSCONFIG register is programming the same value that is already stored in the register. Writes to the devices SYSCONFIG register can be slow, for example, writing to the DMTIMER SYSCONFIG register takes 3 interface clock cycles and 3 functional clock cycles. If the DMTIMER is using the slow 32kHz functional clock this can take ~100us. Furthermore, during boot on an OMAP4430 panda board, I see that there are 100 calls to _idle_sysc(), however, only 3 out of the 100 calls actually write the SYSCONFIG register with a new value. Therefore, to avoid unnecessary writes to device SYSCONFIG registers when idling the device, only write the value if the value has changed. It should be safe to do this on idle as the context of the register will never be lost while the device is active. Verified that suspend, CORE off and retention states are working with this change on OMAP3430 Beagle board. Signed-off-by: Jon Hunter --- arch/arm/mach-omap2/omap_hwmod.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/arm/mach-omap2/omap_hwmod.c b/arch/arm/mach-omap2/omap_hwmod.c index b969ab1..962773b 100644 --- a/arch/arm/mach-omap2/omap_hwmod.c +++ b/arch/arm/mach-omap2/omap_hwmod.c @@ -1389,6 +1389,10 @@ static void _idle_sysc(struct omap_hwmod *oh) if ((sf & SYSC_HAS_SIDLEMODE) && !(oh->flags & HWMOD_SWSUP_SIDLE)) _enable_wakeup(oh, &v); + /* If the cached value is the same as the new value, skip the write */ + if (oh->_sysc_cache == v) + return; + _write_sysconfig(v, oh); }