From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3A2F8C43381 for ; Wed, 20 Feb 2019 10:51:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 158BC2147C for ; Wed, 20 Feb 2019 10:51:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727611AbfBTKvw (ORCPT ); Wed, 20 Feb 2019 05:51:52 -0500 Received: from mail-qk1-f196.google.com ([209.85.222.196]:45281 "EHLO mail-qk1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726317AbfBTKvw (ORCPT ); Wed, 20 Feb 2019 05:51:52 -0500 Received: by mail-qk1-f196.google.com with SMTP id v139so1647117qkb.12; Wed, 20 Feb 2019 02:51:51 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=HbDijqYd6VcGTjPEbGlnYQ5VNZqSZ9FTKXSy74dKt3Y=; b=E826gvrpL4E/w6ZwMXtTLeEpRMr6Xp/6fZwN1QD24OM9t4Mi6UE/CUgiBsQrp7cvPv lEILB03T03kUD/VmwDKQz5TbVbsl0i7K52zY+Pg/JRm1UX25MP6xJgmuiRGRR2ygYaTU OtrmB89b3WcgEYiamDIfffUbC4Gv9xTlaGhzLm0SoGIJAqdP9nn4vFcvGR/fTRRw5Nry xYQkposszndh8kkI+fvtYeO7kDqDDNoTpyZ1hx6Hi2Y1eZWAm+VIfEuM5nVq+kfpvdJD 1s1Z+STMXeBEGt5y/kfbMWSNuDidqBtVJoJGD+OgipmTKUBWdPvwC4NLvUGBLbqaWZdp dOGQ== X-Gm-Message-State: AHQUAua3KdSzpHYEs2i/qcSinG+O2reARebbj2B8iLC9DlzPDWAyrUMA 8xsJumB4+8RGkJkvzszqwILKipP1B2/cr/pvuvY= X-Google-Smtp-Source: AHgI3IbG25UwycjW5eDbZn7BhId3DVZSHrLpQvTau5C8rR6BfYWypsTdmtn4n3G7181xutvguKWUXkkA4wr/ClOsT1c= X-Received: by 2002:ae9:d8c2:: with SMTP id u185mr23165623qkf.107.1550659911265; Wed, 20 Feb 2019 02:51:51 -0800 (PST) MIME-Version: 1.0 References: <20190219182105.19933-1-natechancellor@gmail.com> In-Reply-To: <20190219182105.19933-1-natechancellor@gmail.com> From: Arnd Bergmann Date: Wed, 20 Feb 2019 11:51:34 +0100 Message-ID: Subject: Re: [PATCH] iwlwifi: mvm: Use div64_s64 instead of do_div in iwl_mvm_debug_range_resp To: Nathan Chancellor Cc: Johannes Berg , Emmanuel Grumbach , Luca Coelho , Intel Linux Wireless , Kalle Valo , linux-wireless , Networking , Linux Kernel Mailing List , Nick Desaulniers Content-Type: text/plain; charset="UTF-8" Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, Feb 19, 2019 at 7:22 PM Nathan Chancellor wrote: > > diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/ftm-initiator.c b/drivers/net/wireless/intel/iwlwifi/mvm/ftm-initiator.c > index e9822a3ec373..92b22250eb7d 100644 > --- a/drivers/net/wireless/intel/iwlwifi/mvm/ftm-initiator.c > +++ b/drivers/net/wireless/intel/iwlwifi/mvm/ftm-initiator.c > @@ -462,7 +462,7 @@ static void iwl_mvm_debug_range_resp(struct iwl_mvm *mvm, u8 index, > { > s64 rtt_avg = res->ftm.rtt_avg * 100; > > - do_div(rtt_avg, 6666); > + div64_s64(rtt_avg, 6666); This is wrong: div64_s64 does not modify its argument like do_div(), but it returns the result instead. You also don't want to divide by a 64-bit value when the second argument is a small constant. I think the correct way should be s64 rtt_avg = div_s64(res->ftm.rtt_avg * 100, 6666); If you know that the value is positive, using unsigned types and div_u64() would be slightly faster. Arnd