From patchwork Tue Jan 9 15:18:47 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Crt Mori X-Patchwork-Id: 10152525 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 56792601A1 for ; Tue, 9 Jan 2018 15:19:22 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2F514204BA for ; Tue, 9 Jan 2018 15:19:22 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 23FFA28477; Tue, 9 Jan 2018 15:19:22 +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=ham 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 BADF3204BA for ; Tue, 9 Jan 2018 15:19:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754656AbeAIPTF (ORCPT ); Tue, 9 Jan 2018 10:19:05 -0500 Received: from mail-wm0-f66.google.com ([74.125.82.66]:35940 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758673AbeAIPTD (ORCPT ); Tue, 9 Jan 2018 10:19:03 -0500 Received: by mail-wm0-f66.google.com with SMTP id b76so21498155wmg.1 for ; Tue, 09 Jan 2018 07:19:03 -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=tPghIzf82DovvyEbg66//p+dbuK5L8NUfEzux87L0LE=; b=O71Ci+iY+TzSVv3+biWXO08cgznjQXhSsO4WW8Uz/frBQUoYkE0R8CHi/odER85GBd /lr5VqCoyWv7sgqBpxl4R8CguvH2R9UNdfboxxoTz0fUCJo8LzeYXapwJWSIS9zxqtrs IAW8Ds0qgwindIdHI6x+fJwgCHgoG5i6yTrCQG//Ifv6Q3URAWR07sAtNFX3SlWaM2Iy Bj4Avbyc9XEDYydhNnRsBre37/AREzTvVWjNYd+YdZ+gTi8RihUZeNvUlVropui0mkDT GgBhwAAKwx4eXtcXBriJm9Q34OXzPAtKZgikFYRHVhGg0gVR6h259VgXrngHG3uWZo5Q pANA== 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=tPghIzf82DovvyEbg66//p+dbuK5L8NUfEzux87L0LE=; b=eCGLHnO7w2S2vaAqaRuTBo/fOWlIX8Un9Kitckoan1XRFR8+/SzhtcpLNDk4cZHft4 mBgLiMMXbLxBcKwRbODgo9QfIiG2+tAvmQhPA3i0gYXC0aOhe10Lq3epri02uZ1O0wZ1 XGqcXqBqDHYZ9vU63OM1NebBRnybsMwRyQ4ZGBYmv3A4iQOyEVaYsnKIYYT7/wy1QrfJ x0/T6laJuy6pddyoRVdmCNdiqHOVacmxcncubnTSLbv/BJ3MI3Pmr5IEGtldv82p5jz6 GdYblDwCtIfWsptnBjRlOd/0riDigTwpNMithUONRIOf5szf/h6l808Hb18g9/ldc2Sz FCag== X-Gm-Message-State: AKGB3mIX51+PpWl2FCeCizVrcJ9zPbpKmYFAEPLIaWdGgUZnWRcWRYdo MqhvBsOpFKdhR2wZgJx4zgSWIw== X-Google-Smtp-Source: ACJfBov9iE06djsHk3m9mvhs9L5LG/gvlvDzNj49x6OoTWTjepAdR/WNyiuiKDpRIHSVm/bBk2nE9A== X-Received: by 10.28.85.193 with SMTP id j184mr12928616wmb.56.1515511142691; Tue, 09 Jan 2018 07:19:02 -0800 (PST) Received: from pc3729.tess.elex.be ([194.150.35.21]) by smtp.gmail.com with ESMTPSA id v195sm13379534wmf.25.2018.01.09.07.19.00 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 09 Jan 2018 07:19:01 -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 v12 1/3] lib: Add strongly typed 64bit int_sqrt Date: Tue, 9 Jan 2018 16:18:47 +0100 Message-Id: <20180109151847.30258-1-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. Signed-off-by: Crt Mori Acked-by: Joe Perches --- include/linux/kernel.h | 9 +++++++++ lib/int_sqrt.c | 32 ++++++++++++++++++++++++++++++++ 2 files changed, 41 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..737fca54bb02 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 +37,34 @@ 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; + u32 y = 0; + + if (x <= 1) + return 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