From patchwork Thu Jun 12 15:58:28 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Peter De Schrijver X-Patchwork-Id: 4343051 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 319DBBEEAA for ; Thu, 12 Jun 2014 16:01:33 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 49CC92035D for ; Thu, 12 Jun 2014 16:01:29 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 12F0A20373 for ; Thu, 12 Jun 2014 16:01:22 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1Wv7PX-0004qe-6k; Thu, 12 Jun 2014 15:59:31 +0000 Received: from hqemgate15.nvidia.com ([216.228.121.64]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1Wv7PI-0004g2-DM for linux-arm-kernel@lists.infradead.org; Thu, 12 Jun 2014 15:59:16 +0000 Received: from hqnvupgp08.nvidia.com (Not Verified[216.228.121.13]) by hqemgate15.nvidia.com id ; Thu, 12 Jun 2014 08:58:02 -0700 Received: from hqemhub02.nvidia.com ([172.20.12.94]) by hqnvupgp08.nvidia.com (PGP Universal service); Thu, 12 Jun 2014 08:53:39 -0700 X-PGP-Universal: processed; by hqnvupgp08.nvidia.com on Thu, 12 Jun 2014 08:53:39 -0700 Received: from hqnvemgw01.nvidia.com (172.20.150.20) by hqemhub02.nvidia.com (172.20.150.31) with Microsoft SMTP Server id 8.3.342.0; Thu, 12 Jun 2014 08:58:57 -0700 Received: from thelma.nvidia.com (Not Verified[172.16.212.77]) by hqnvemgw01.nvidia.com with MailMarshal (v7,1,2,5326) id ; Thu, 12 Jun 2014 08:58:57 -0700 Received: from tbergstrom-lnx.nvidia.com (tbergstrom-lnx.nvidia.com [10.21.24.170]) by thelma.nvidia.com (8.13.8+Sun/8.8.8) with ESMTP id s5CFwcpq000980; Thu, 12 Jun 2014 08:58:55 -0700 (PDT) From: Peter De Schrijver To: Peter De Schrijver Subject: [PATCH v2 2/3] ARM: choose highest resolution delay timer Date: Thu, 12 Jun 2014 18:58:28 +0300 Message-ID: <1402588713-18766-3-git-send-email-pdeschrijver@nvidia.com> X-Mailer: git-send-email 1.7.7.rc0.72.g4b5ea.dirty In-Reply-To: <1402588713-18766-1-git-send-email-pdeschrijver@nvidia.com> References: <1402588713-18766-1-git-send-email-pdeschrijver@nvidia.com> X-NVConfidentiality: public MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20140612_085916_456580_D6E8E1D3 X-CRM114-Status: GOOD ( 15.91 ) X-Spam-Score: -0.7 (/) Cc: Russell King , Stephen Warren , Daniel Lezcano , linux-kernel@vger.kernel.org, Paul Gortmaker , Thierry Reding , linux-tegra@vger.kernel.org, Thomas Gleixner , linux-arm-kernel@lists.infradead.org X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-2.5 required=5.0 tests=BAYES_00,RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP In case there are several possible delay timers, choose the one with the highest resolution. This code relies on the fact secondary CPUs have not yet been brought online when register_current_timer_delay() is called. This is ensured by implementing calibration_delay_done(), Signed-off-by: Peter De Schrijver --- arch/arm/lib/delay.c | 26 ++++++++++++++++++++++---- 1 files changed, 22 insertions(+), 4 deletions(-) diff --git a/arch/arm/lib/delay.c b/arch/arm/lib/delay.c index 5306de3..312d43e 100644 --- a/arch/arm/lib/delay.c +++ b/arch/arm/lib/delay.c @@ -19,6 +19,7 @@ * Author: Will Deacon */ +#include #include #include #include @@ -36,6 +37,7 @@ struct arm_delay_ops arm_delay_ops = { static const struct delay_timer *delay_timer; static bool delay_calibrated; +static u64 delay_res; int read_current_timer(unsigned long *timer_val) { @@ -47,6 +49,11 @@ int read_current_timer(unsigned long *timer_val) } EXPORT_SYMBOL_GPL(read_current_timer); +static inline u64 cyc_to_ns(u64 cyc, u32 mult, u32 shift) +{ + return (cyc * mult) >> shift; +} + static void __timer_delay(unsigned long cycles) { cycles_t start = get_cycles(); @@ -69,18 +76,24 @@ static void __timer_udelay(unsigned long usecs) void __init register_current_timer_delay(const struct delay_timer *timer) { - if (!delay_calibrated) { - pr_info("Switching to timer-based delay loop\n"); + u32 new_mult, new_shift; + u64 res; + + clocks_calc_mult_shift(&new_mult, &new_shift, timer->freq, + NSEC_PER_SEC, 3600); + res = cyc_to_ns(1ULL, new_mult, new_shift); + + if (!delay_calibrated && (!delay_res || (res < delay_res))) { + pr_info("Switching to timer-based delay loop, resolution %lluns\n", res); delay_timer = timer; lpj_fine = timer->freq / HZ; + delay_res = res; /* cpufreq may scale loops_per_jiffy, so keep a private copy */ arm_delay_ops.ticks_per_jiffy = lpj_fine; arm_delay_ops.delay = __timer_delay; arm_delay_ops.const_udelay = __timer_const_udelay; arm_delay_ops.udelay = __timer_udelay; - - delay_calibrated = true; } else { pr_info("Ignoring duplicate/late registration of read_current_timer delay\n"); } @@ -91,3 +104,8 @@ unsigned long calibrate_delay_is_known(void) delay_calibrated = true; return lpj_fine; } + +void calibration_delay_done(void) +{ + delay_calibrated = true; +}