From patchwork Thu Jan 11 10:19:57 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Crt Mori X-Patchwork-Id: 10157783 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 974FD60170 for ; Thu, 11 Jan 2018 10:20:28 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9521E28733 for ; Thu, 11 Jan 2018 10:20:26 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 9189B28770; Thu, 11 Jan 2018 10:20:26 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=2.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_HI,T_DKIM_INVALID autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 72300286F5 for ; Thu, 11 Jan 2018 10:20:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933142AbeAKKUH (ORCPT ); Thu, 11 Jan 2018 05:20:07 -0500 Received: from mail-wr0-f195.google.com ([209.85.128.195]:42724 "EHLO mail-wr0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933125AbeAKKUF (ORCPT ); Thu, 11 Jan 2018 05:20:05 -0500 Received: by mail-wr0-f195.google.com with SMTP id e41so1329885wre.9 for ; Thu, 11 Jan 2018 02:20:05 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=melexis.com; s=google; h=from:to:cc:subject:date:message-id; bh=BIcr/nRqRXzDS6iSP4oQ8lrDFL0KlDYnJDhvy8TBgD0=; b=q8sRlwSTWmIT028OkyNvYsjgCSThhAFgOwOsSSzB71xjx9rJDD8gi+Y4BT7vGvMd17 ZJf1Ms3zb+6L7KRucJG20BmQiNrUeBOv7xryk6beGM3ED8+ow0iAk2UtKUyuR5g+WxYy iqbXviHJS7lx03SDdTu6Pn9y0cFA9bGsWdxLVTEGd0FpYksW+QSyTFmVU2/9yWEtGyRg FIRreBu85ZZpaTWKY7TKdrVlrvZKJjzZrvw3MtfWfWxmsGvlAbnkU5+2M4A6yE73I1UB evnnZm2VT125ePiuL2dbmlIFTXQNGNVqheDOnSb9ckyYr1s78EGFkVeju1fD6r2sTIq5 v0sA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=BIcr/nRqRXzDS6iSP4oQ8lrDFL0KlDYnJDhvy8TBgD0=; b=ohwEq3zrZv/nh43JM2w+M2/BQGEvUqU9bu+N+zZLqIk/n5sLyDaYwZdwQGZSOapRK4 TSZAwvJxFZ0VNuT5uI5V9iqY9+t8JA6HLWK/RH51FP39yA1yrI5JrAuTQKmQI2HEC1ZH l9rcmf2UzDzJDZUGQ1eJnaEGwWpF4Q8T53XSFmT3JTeec90w/qGWPFoJ3HYKIobm5Nur f2FFuE1zRn6KGuiV8+jgoJ0zj1osD89HJ53AMhSYXOp8ZD31dMW7I+9pUWeRMhWzaYZP +FbHqeXTipSFN4dzgh9ta+KFfzf7C2+jjxEBFlazs/HKzadLsnUCJY6X04AQfUB32fSj 2ztA== X-Gm-Message-State: AKGB3mJeALqZ+hurlcfBo0Bxk311N2ZUznJNQuMoWtNpV1T/RlW62bhG MbgJV6VyOFoU7CJCA+z7dKd3rA== X-Google-Smtp-Source: ACJfBos/LbUJA68FkpYzlrLRSPU8vdHRh92XvXvj5hnqKrsKP7MqhHodnqE0dv8EFBHWXFuQfaXGgg== X-Received: by 10.223.156.196 with SMTP id h4mr18624826wre.17.1515666004425; Thu, 11 Jan 2018 02:20:04 -0800 (PST) Received: from pc3729.tess.elex.be ([194.150.35.21]) by smtp.gmail.com with ESMTPSA id m127sm187527wmm.48.2018.01.11.02.20.02 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 11 Jan 2018 02:20:03 -0800 (PST) From: Crt Mori To: Jonathan Cameron Cc: Ingo Molnar , Andrew Morton , Kees Cook , Rusty Russell , Ian Abbott , Larry Finger , Niklas Soderlund , Thomas Gleixner , Krzysztof Kozlowski , Masahiro Yamada , linux-kernel@vger.kernel.org, linux-iio@vger.kernel.org, Peter Zijlstra , Joe Perches , David Laight , Crt Mori Subject: [PATCH v13 1/3] lib: Add strongly typed 64bit int_sqrt Date: Thu, 11 Jan 2018 11:19:57 +0100 Message-Id: <20180111101957.27290-1-cmo@melexis.com> X-Mailer: git-send-email 2.15.0 Sender: linux-iio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-iio@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP There is no option to perform 64bit integer sqrt on 32bit platform. Added stronger typed int_sqrt64 enables the 64bit calculations to be performed on 32bit platforms. Using same algorithm as int_sqrt() with strong typing provides enough precision also on 32bit platforms, but it sacrifices some performance. In case values are smaller than ULONG_MAX the standard int_sqrt is used for calculation to maximize the performance due to more native calculations. Signed-off-by: Crt Mori --- include/linux/kernel.h | 9 +++++++++ lib/int_sqrt.c | 31 +++++++++++++++++++++++++++++++ 2 files changed, 40 insertions(+) diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 0ad4c3044cf9..e4a3dc64e650 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -460,6 +460,15 @@ extern int func_ptr_is_kernel_text(void *ptr); unsigned long int_sqrt(unsigned long); +#if BITS_PER_LONG < 64 +u32 int_sqrt64(u64 x); +#else +static inline u32 int_sqrt64(u64 x) +{ + return (u32)int_sqrt(x); +} +#endif + extern void bust_spinlocks(int yes); extern int oops_in_progress; /* If set, an oops, panic(), BUG() or die() is in progress */ extern int panic_timeout; diff --git a/lib/int_sqrt.c b/lib/int_sqrt.c index 1ef4cc344977..77386bc611d0 100644 --- a/lib/int_sqrt.c +++ b/lib/int_sqrt.c @@ -7,6 +7,7 @@ #include #include +#include /** * int_sqrt - rough approximation to sqrt @@ -36,3 +37,33 @@ unsigned long int_sqrt(unsigned long x) return y; } EXPORT_SYMBOL(int_sqrt); + +#if BITS_PER_LONG < 64 +/** + * int_sqrt64 - strongly typed int_sqrt function when minimum 64 bit input + * is expected. + * @x: 64bit integer of which to calculate the sqrt + */ +u32 int_sqrt64(u64 x) +{ + u64 b, m, y = 0; + + if (x <= ULONG_MAX) + return int_sqrt((unsigned long) x); + + m = 1ULL << (fls64(x) & ~1ULL); + while (m != 0) { + b = y + m; + y >>= 1; + + if (x >= b) { + x -= b; + y += m; + } + m >>= 2; + } + + return y; +} +EXPORT_SYMBOL(int_sqrt64); +#endif