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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 2742EC3279B for ; Fri, 6 Jul 2018 13:59:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D263B23E56 for ; Fri, 6 Jul 2018 13:59:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D263B23E56 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=embeddedor.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932908AbeGFN7S (ORCPT ); Fri, 6 Jul 2018 09:59:18 -0400 Received: from gateway22.websitewelcome.com ([192.185.47.125]:21298 "EHLO gateway22.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932310AbeGFN7O (ORCPT ); Fri, 6 Jul 2018 09:59:14 -0400 Received: from cm15.websitewelcome.com (cm15.websitewelcome.com [100.42.49.9]) by gateway22.websitewelcome.com (Postfix) with ESMTP id 5397968C3 for ; Fri, 6 Jul 2018 08:59:13 -0500 (CDT) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id bRFpfhVjfbXuJbRGCfrRzR; Fri, 06 Jul 2018 08:59:12 -0500 X-Authority-Reason: nr=8 Received: from [189.250.65.56] (port=45576 helo=[192.168.1.71]) by gator4166.hostgator.com with esmtpsa (TLSv1.2:ECDHE-RSA-AES128-GCM-SHA256:128) (Exim 4.91) (envelope-from ) id 1fbRFo-000QY5-Sh; Fri, 06 Jul 2018 08:58:33 -0500 Subject: Re: [PATCH net-next] stmmac: fix signed 64-bit division To: Arnd Bergmann , Giuseppe Cavallaro , Alexandre Torgue , Jose Abreu , "David S. Miller" Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20180706133646.312427-1-arnd@arndb.de> From: "Gustavo A. R. Silva" Openpgp: preference=signencrypt Autocrypt: addr=gustavo@embeddedor.com; keydata= xsFNBFssHAwBEADIy3ZoPq3z5UpsUknd2v+IQud4TMJnJLTeXgTf4biSDSrXn73JQgsISBwG 2Pm4wnOyEgYUyJd5tRWcIbsURAgei918mck3tugT7AQiTUN3/5aAzqe/4ApDUC+uWNkpNnSV tjOx1hBpla0ifywy4bvFobwSh5/I3qohxDx+c1obd8Bp/B/iaOtnq0inli/8rlvKO9hp6Z4e DXL3PlD0QsLSc27AkwzLEc/D3ZaqBq7ItvT9Pyg0z3Q+2dtLF00f9+663HVC2EUgP25J3xDd 496SIeYDTkEgbJ7WYR0HYm9uirSET3lDqOVh1xPqoy+U9zTtuA9NQHVGk+hPcoazSqEtLGBk YE2mm2wzX5q2uoyptseSNceJ+HE9L+z1KlWW63HhddgtRGhbP8pj42bKaUSrrfDUsicfeJf6 m1iJRu0SXYVlMruGUB1PvZQ3O7TsVfAGCv85pFipdgk8KQnlRFkYhUjLft0u7CL1rDGZWDDr NaNj54q2CX9zuSxBn9XDXvGKyzKEZ4NY1Jfw+TAMPCp4buawuOsjONi2X0DfivFY+ZsjAIcx qQMglPtKk/wBs7q2lvJ+pHpgvLhLZyGqzAvKM1sVtRJ5j+ARKA0w4pYs5a5ufqcfT7dN6TBk LXZeD9xlVic93Ju08JSUx2ozlcfxq+BVNyA+dtv7elXUZ2DrYwARAQABzSxHdXN0YXZvIEEu IFIuIFNpbHZhIDxndXN0YXZvQGVtYmVkZGVkb3IuY29tPsLBfQQTAQgAJwUCWywcDAIbIwUJ CWYBgAULCQgHAgYVCAkKCwIEFgIDAQIeAQIXgAAKCRBHBbTLRwbbMZ6tEACk0hmmZ2FWL1Xi l/bPqDGFhzzexrdkXSfTTZjBV3a+4hIOe+jl6Rci/CvRicNW4H9yJHKBrqwwWm9fvKqOBAg9 obq753jydVmLwlXO7xjcfyfcMWyx9QdYLERTeQfDAfRqxir3xMeOiZwgQ6dzX3JjOXs6jHBP cgry90aWbaMpQRRhaAKeAS14EEe9TSIly5JepaHoVdASuxklvOC0VB0OwNblVSR2S5i5hSsh ewbOJtwSlonsYEj4EW1noQNSxnN/vKuvUNegMe+LTtnbbocFQ7dGMsT3kbYNIyIsp42B5eCu JXnyKLih7rSGBtPgJ540CjoPBkw2mCfhj2p5fElRJn1tcX2McsjzLFY5jK9RYFDavez5w3lx JFgFkla6sQHcrxH62gTkb9sUtNfXKucAfjjCMJ0iuQIHRbMYCa9v2YEymc0k0RvYr43GkA3N PJYd/vf9vU7VtZXaY4a/dz1d9dwIpyQARFQpSyvt++R74S78eY/+lX8wEznQdmRQ27kq7BJS R20KI/8knhUNUJR3epJu2YFT/JwHbRYC4BoIqWl+uNvDf+lUlI/D1wP+lCBSGr2LTkQRoU8U 64iK28BmjJh2K3WHmInC1hbUucWT7Swz/+6+FCuHzap/cjuzRN04Z3Fdj084oeUNpP6+b9yW e5YnLxF8ctRAp7K4yVlvA87BTQRbLBwMARAAsHCE31Ffrm6uig1BQplxMV8WnRBiZqbbsVJB H1AAh8tq2ULl7udfQo1bsPLGGQboJSVN9rckQQNahvHAIK8ZGfU4Qj8+CER+fYPp/MDZj+t0 DbnWSOrG7z9HIZo6PR9z4JZza3Hn/35jFggaqBtuydHwwBANZ7A6DVY+W0COEU4of7CAahQo 5NwYiwS0lGisLTqks5R0Vh+QpvDVfuaF6I8LUgQR/cSgLkR//V1uCEQYzhsoiJ3zc1HSRyOP otJTApqGBq80X0aCVj1LOiOF4rrdvQnj6iIlXQssdb+WhSYHeuJj1wD0ZlC7ds5zovXh+FfF l5qH5RFY/qVn3mNIVxeO987WSF0jh+T5ZlvUNdhedGndRmwFTxq2Li6GNMaolgnpO/CPcFpD jKxY/HBUSmaE9rNdAa1fCd4RsKLlhXda+IWpJZMHlmIKY8dlUybP+2qDzP2lY7kdFgPZRU+e zS/pzC/YTzAvCWM3tDgwoSl17vnZCr8wn2/1rKkcLvTDgiJLPCevqpTb6KFtZosQ02EGMuHQ I6Zk91jbx96nrdsSdBLGH3hbvLvjZm3C+fNlVb9uvWbdznObqcJxSH3SGOZ7kCHuVmXUcqoz ol6ioMHMb+InrHPP16aVDTBTPEGwgxXI38f7SUEn+NpbizWdLNz2hc907DvoPm6HEGCanpcA EQEAAcLBZQQYAQgADwUCWywcDAIbDAUJCWYBgAAKCRBHBbTLRwbbMdsZEACUjmsJx2CAY+QS UMebQRFjKavwXB/xE7fTt2ahuhHT8qQ/lWuRQedg4baInw9nhoPE+VenOzhGeGlsJ0Ys52sd XvUjUocKgUQq6ekOHbcw919nO5L9J2ejMf/VC/quN3r3xijgRtmuuwZjmmi8ct24TpGeoBK4 WrZGh/1hAYw4ieARvKvgjXRstcEqM5thUNkOOIheud/VpY+48QcccPKbngy//zNJWKbRbeVn imua0OpqRXhCrEVm/xomeOvl1WK1BVO7z8DjSdEBGzbV76sPDJb/fw+y+VWrkEiddD/9CSfg fBNOb1p1jVnT2mFgGneIWbU0zdDGhleI9UoQTr0e0b/7TU+Jo6TqwosP9nbk5hXw6uR5k5PF 8ieyHVq3qatJ9K1jPkBr8YWtI5uNwJJjTKIA1jHlj8McROroxMdI6qZ/wZ1ImuylpJuJwCDC ORYf5kW61fcrHEDlIvGc371OOvw6ejF8ksX5+L2zwh43l/pKkSVGFpxtMV6d6J3eqwTafL86 YJWH93PN+ZUh6i6Rd2U/i8jH5WvzR57UeWxE4P8bQc0hNGrUsHQH6bpHV2lbuhDdqo+cM9eh GZEO3+gCDFmKrjspZjkJbB5Gadzvts5fcWGOXEvuT8uQSvl+vEL0g6vczsyPBtqoBLa9SNrS VtSixD1uOgytAP7RWS474w== Message-ID: <1ec22f16-f10d-6e4c-e844-7c66ca47ec58@embeddedor.com> Date: Fri, 6 Jul 2018 08:58:21 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <20180706133646.312427-1-arnd@arndb.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - gator4166.hostgator.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - embeddedor.com X-BWhitelist: no X-Source-IP: 189.250.65.56 X-Source-L: No X-Exim-ID: 1fbRFo-000QY5-Sh X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: ([192.168.1.71]) [189.250.65.56]:45576 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 10 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Arnd, On 07/06/2018 08:36 AM, Arnd Bergmann wrote: > I link error on 32-bit ARM points to yet another arithmetic bug: > > drivers/net/ethernet/stmicro/stmmac/stmmac_tc.o: In function `tc_setup_cbs': > stmmac_tc.c:(.text+0x148): undefined reference to `__aeabi_uldivmod' > stmmac_tc.c:(.text+0x1fc): undefined reference to `__aeabi_uldivmod' > stmmac_tc.c:(.text+0x308): undefined reference to `__aeabi_uldivmod' > stmmac_tc.c:(.text+0x320): undefined reference to `__aeabi_uldivmod' > stmmac_tc.c:(.text+0x33c): undefined reference to `__aeabi_uldivmod' > drivers/net/ethernet/stmicro/stmmac/stmmac_tc.o:stmmac_tc.c:(.text+0x3a4): more undefined references to `__aeabi_uldivmod' follow > > I observe that the last change to add the 'ul' prefix was incorrect, > as it did not turn the result of the multiplication into a 64-bit > expression on 32-bit architectures. Further, it seems that the > do_div() macro gets confused by the fact that we pass a signed > variable rather than unsigned into it. > Thanks for this fix. > This changes the code to instead use the div_s64() helper that is > meant for signed division, along with changing the constant suffix > to 'll' to actually make it a 64-bit argument everywhere, fixing > both of the issues I pointed out. > > I'm not completely convinced that this makes the code correct, but > I'm fairly sure that we have two problems less than before. > > Fixes: 1f705bc61aee ("net: stmmac: Add support for CBS QDISC") > Fixes: c18a9c096683 ("net: stmmac_tc: use 64-bit arithmetic instead of 32-bit") > Signed-off-by: Arnd Bergmann Acked-by: Gustavo A. R. Silva > --- > drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c | 10 ++++------ > 1 file changed, 4 insertions(+), 6 deletions(-) > > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c > index 8fedc288d138..1a96dd9c1091 100644 > --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c > +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_tc.c > @@ -321,18 +321,16 @@ static int tc_setup_cbs(struct stmmac_priv *priv, > speed_div = (priv->speed == SPEED_100) ? 100000 : 1000000; > > /* Final adjustments for HW */ > - value = qopt->idleslope * 1024UL * ptr; > - do_div(value, speed_div); > + value = div_s64(qopt->idleslope * 1024ll * ptr, speed_div); > priv->plat->tx_queues_cfg[queue].idle_slope = value & GENMASK(31, 0); > > - value = -qopt->sendslope * 1024UL * ptr; > - do_div(value, speed_div); > + value = div_s64(-qopt->sendslope * 1024ll * ptr, speed_div); > priv->plat->tx_queues_cfg[queue].send_slope = value & GENMASK(31, 0); > > - value = qopt->hicredit * 1024UL * 8; > + value = qopt->hicredit * 1024ll * 8; > priv->plat->tx_queues_cfg[queue].high_credit = value & GENMASK(31, 0); > > - value = qopt->locredit * 1024UL * 8; > + value = qopt->locredit * 1024ll * 8; > priv->plat->tx_queues_cfg[queue].low_credit = value & GENMASK(31, 0); > > ret = stmmac_config_cbs(priv, priv->hw, >