From patchwork Wed Dec 20 15:48:41 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Crt Mori X-Patchwork-Id: 10125849 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 7030660388 for ; Wed, 20 Dec 2017 15:48:54 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 609DE297E0 for ; Wed, 20 Dec 2017 15:48:54 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 4EB67297FC; Wed, 20 Dec 2017 15:48:54 +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 A2DA92980C for ; Wed, 20 Dec 2017 15:48:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755563AbdLTPsv (ORCPT ); Wed, 20 Dec 2017 10:48:51 -0500 Received: from mail-wm0-f66.google.com ([74.125.82.66]:36248 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755559AbdLTPsu (ORCPT ); Wed, 20 Dec 2017 10:48:50 -0500 Received: by mail-wm0-f66.google.com with SMTP id b76so10670119wmg.1 for ; Wed, 20 Dec 2017 07:48:49 -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=u3ukZ8qp9NFALuWCqHlnroaTtMoWK7z/qCa4DPEsamE=; b=onVJq3r/cFkGlCN9kcC6SN2IAyDxOKB7Zvk+hKCFTRbjY3rk5Qmefc5YeGge5935aj wflWcYxnSG9CfKNxhfVQB6p7Wm4a403T8pQTDWwCjQ9ih7YpCcw7wDtnH+mfWTW+k0E8 ctelHai+sbPoA81DGU6VJAUijdRBPVNOJ3JrooEo5T0f70oQTM7kdktDeTU+B7CiRYD/ ZV2kKlGUdW7uognQnzBI6tW06JWrUIpfK1eZaduQiwSN9fSGZhRK5XnaOyblyDEreO1G xxPz0j6/4bx3aImN9HsOEzBuczlzsWka4aO512zTeDiFd1icFl5uOtZ9nAXiCuXG8tQ0 3r9A== 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=u3ukZ8qp9NFALuWCqHlnroaTtMoWK7z/qCa4DPEsamE=; b=GL/xuz0Tj1kd4Gx7up5LtVP3rH2Ron+NRQNTr54WQiqcxGGq+kwj/QkoCqnu1qi6QT HvL6DVHLdKQtenL+4og4dNQGHapVRjvzQ0Ed1vPNhWTAVqaARSM+ZSyAKPUcxlwKAtYI 8Haqad1Mj495QY7UN9aSBEOWnMjEFTTwllwv2z+95FlPeRQzkbc/jWeIvm95ezPNpCA1 B3PJn5ThBgiyFYeJSOGZF6K4ETQZs8FhVhtgfZt0eL7W60rUhCUyxkJEcamTFXSJOkIZ V8u/gPbAzG5lqN3D4Owqb1pQvz+s1Ki6afk++TyHq1Q0OVB4lusEOCal4Npy5ZYrGxMS 3Liw== X-Gm-Message-State: AKGB3mL9Q+WWpilYcTVKe3lL7NKa5Il3MoPjlhEUNlFAJ9xdq2u4gzzM ZBFBTtweUyOEysZANVvTsgblbQ== X-Google-Smtp-Source: ACJfBosMnpYOt4mGISiR6VSdG+0D4kbF1yDRyI3+IwhJ2b83WZy3XZcdVUS8WU2VZZaiXKEZj2Vf1Q== X-Received: by 10.80.201.196 with SMTP id c4mr5985515edi.56.1513784929051; Wed, 20 Dec 2017 07:48:49 -0800 (PST) Received: from localhost.localdomain (ptr-4xfub6rwgakpug564fr.18120a2.ip6.access.telenet.be. [2a02:1810:a444:c300:4527:fd81:32c2:e0f7]) by smtp.gmail.com with ESMTPSA id t19sm14405095edh.49.2017.12.20.07.48.47 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 20 Dec 2017 07:48:47 -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 , Crt Mori Subject: [PATCH v11 1/3] lib: Add strongly typed 64bit int_sqrt Date: Wed, 20 Dec 2017 16:48:41 +0100 Message-Id: <20171220154841.24089-1-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 --- 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..184da54677ec 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 <= 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