From patchwork Mon Apr 1 20:58:34 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Rob Herring X-Patchwork-Id: 2372761 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 2C1263FD40 for ; Mon, 1 Apr 2013 21:02:12 +0000 (UTC) Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1UMlow-0005ri-9V; Mon, 01 Apr 2013 20:59:14 +0000 Received: from mail-ve0-f175.google.com ([209.85.128.175]) by merlin.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1UMloZ-0005ob-8o for linux-arm-kernel@lists.infradead.org; Mon, 01 Apr 2013 20:58:51 +0000 Received: by mail-ve0-f175.google.com with SMTP id pb11so3019330veb.20 for ; Mon, 01 Apr 2013 13:58:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=x-received:from:to:cc:subject:date:message-id:x-mailer:in-reply-to :references; bh=drvFQQUJI83rJ2sFe84vMvcgG8bodIO03VXVIWblxS4=; b=Q+9xmO2SbJShD1g9otJ4THLsb17ir2EigzErNvnN0/fwTVJL/cc/6p8HqrEPO78Jpl dBl1xM25PnBpUm5BxP0Hnrrpty9eGOaryq5nJ8c/5dqwdgEk1/h+43o1SVme2x26nw6r F6yTU6+pF+hZcEQMI3/7vRg9gksxiiL86Br75nz8cJoOpVLQpXIOASvYD74WwPFJK4Ca wRzYEH9l80mFmp8rN2Ashzi0qqMsSDWtGfYK4D5m6yMO2tPkYkgZwqdB1VhKrp7T8GNh NoEW2Ycfa9bc+y+swgiu9koJT857CVLka2ywbpOM4fz1gzCavElw0j54j65BKWuNQT9V hnMQ== X-Received: by 10.52.23.38 with SMTP id j6mr8926549vdf.121.1364849929379; Mon, 01 Apr 2013 13:58:49 -0700 (PDT) Received: from rob-laptop.calxeda.com ([173.226.190.126]) by mx.google.com with ESMTPS id l18sm15810836vdh.10.2013.04.01.13.58.48 (version=TLSv1.1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Mon, 01 Apr 2013 13:58:48 -0700 (PDT) From: Rob Herring To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v2 3/3] ARM: arch_timer: use full 64-bit counter for sched_clock Date: Mon, 1 Apr 2013 15:58:34 -0500 Message-Id: <1364849914-26420-4-git-send-email-robherring2@gmail.com> X-Mailer: git-send-email 1.7.10.4 In-Reply-To: <1364849914-26420-1-git-send-email-robherring2@gmail.com> References: <1364849914-26420-1-git-send-email-robherring2@gmail.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20130401_165851_390323_776EB0FC X-CRM114-Status: GOOD ( 12.13 ) X-Spam-Score: -2.5 (--) X-Spam-Report: SpamAssassin version 3.3.2 on merlin.infradead.org summary: Content analysis details: (-2.5 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.7 RCVD_IN_DNSWL_LOW RBL: Sender listed at http://www.dnswl.org/, low trust [209.85.128.175 listed in list.dnswl.org] 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (robherring2[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record 0.2 FREEMAIL_ENVFROM_END_DIGIT Envelope-from freemail username ends in digit (robherring2[at]gmail.com) -1.9 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature Cc: Mark Rutland , Russell King , Rob Herring , arm@kernel.org, John Stultz , Thomas Gleixner X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org From: Rob Herring Only 32-bits of the arch timer were being used and wrapping was needlessly being done in s/w. By using the full counter (56-64 bits), we don't need to deal with wrapping and can simplify the implementation when using arch timer. Signed-off-by: Rob Herring --- arch/arm/kernel/arch_timer.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/arch/arm/kernel/arch_timer.c b/arch/arm/kernel/arch_timer.c index d957a51..a7536d4 100644 --- a/arch/arm/kernel/arch_timer.c +++ b/arch/arm/kernel/arch_timer.c @@ -22,9 +22,11 @@ static unsigned long arch_timer_read_counter_long(void) return arch_timer_read_counter(); } -static u32 arch_timer_read_counter_u32(void) +static u32 sched_clock_mult __read_mostly; + +static unsigned long long notrace arch_timer_sched_clock(void) { - return arch_timer_read_counter(); + return arch_timer_read_counter() * sched_clock_mult; } static struct delay_timer arch_delay_timer; @@ -52,10 +54,13 @@ int __init arch_timer_of_register(void) int __init arch_timer_sched_clock_init(void) { - if (arch_timer_get_rate() == 0) + u32 arch_timer_rate = arch_timer_get_rate(); + + if (arch_timer_rate == 0) return -ENXIO; - setup_sched_clock(arch_timer_read_counter_u32, - 32, arch_timer_get_rate()); + /* Cache the sched_clock multiplier to save a divide in the hot path. */ + sched_clock_mult = NSEC_PER_SEC / arch_timer_rate; + sched_clock_func = arch_timer_sched_clock; return 0; }