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=-5.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 EE3E5C433E1 for ; Wed, 19 Aug 2020 02:09:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C43E02067C for ; Wed, 19 Aug 2020 02:09:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=samsung.com header.i=@samsung.com header.b="ff8ctMz7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726786AbgHSCJI (ORCPT ); Tue, 18 Aug 2020 22:09:08 -0400 Received: from mailout3.samsung.com ([203.254.224.33]:37395 "EHLO mailout3.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726539AbgHSCJH (ORCPT ); Tue, 18 Aug 2020 22:09:07 -0400 Received: from epcas2p1.samsung.com (unknown [182.195.41.53]) by mailout3.samsung.com (KnoxPortal) with ESMTP id 20200819020903epoutp03a905826be8557252bbe67146cf5e3c50~siU-Do3Cm1253412534epoutp03b for ; Wed, 19 Aug 2020 02:09:03 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 mailout3.samsung.com 20200819020903epoutp03a905826be8557252bbe67146cf5e3c50~siU-Do3Cm1253412534epoutp03b DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=samsung.com; s=mail20170921; t=1597802943; bh=kxbo7eMgrK3SBvMvlw7cM5qlajMPHGPiUFNSCKIGvZU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=ff8ctMz7mHT6Hov/3OsBzOUh0n5phfoDsae+pmZ42N3YIXZaZDZbNsHgj2b+WGr3W jThvtfDyRAbb28THWE+tM2xSm8zt7XpffWXomWzgbRXl4kWoV75ZLJISwxpa/fQA8S fns5Htsk2DEpwXOV7PAWo9znB9JuF2rp716yV53I= Received: from epsnrtp4.localdomain (unknown [182.195.42.165]) by epcas2p4.samsung.com (KnoxPortal) with ESMTP id 20200819020901epcas2p456f4f40ee45dcf83af820f0cc78a918b~siU9N99ZT1684716847epcas2p4G; Wed, 19 Aug 2020 02:09:01 +0000 (GMT) Received: from epsmges2p4.samsung.com (unknown [182.195.40.187]) by epsnrtp4.localdomain (Postfix) with ESMTP id 4BWWRb44FszMqYkr; Wed, 19 Aug 2020 02:08:59 +0000 (GMT) Received: from epcas2p2.samsung.com ( [182.195.41.54]) by epsmges2p4.samsung.com (Symantec Messaging Gateway) with SMTP id 68.9B.27013.BB98C3F5; Wed, 19 Aug 2020 11:08:59 +0900 (KST) Received: from epsmtrp1.samsung.com (unknown [182.195.40.13]) by epcas2p1.samsung.com (KnoxPortal) with ESMTPA id 20200819020857epcas2p1681b773d1393c7c29a8bc61606061922~siU54uxFS0037000370epcas2p1A; Wed, 19 Aug 2020 02:08:57 +0000 (GMT) Received: from epsmgms1p1new.samsung.com (unknown [182.195.42.41]) by epsmtrp1.samsung.com (KnoxPortal) with ESMTP id 20200819020857epsmtrp1991dcb6deeb4dc6574e8836dc5a6d310~siU5zoEM11046710467epsmtrp1D; Wed, 19 Aug 2020 02:08:57 +0000 (GMT) X-AuditID: b6c32a48-d35ff70000006985-29-5f3c89bbeff8 Received: from epsmtip1.samsung.com ( [182.195.34.30]) by epsmgms1p1new.samsung.com (Symantec Messaging Gateway) with SMTP id 5E.FE.08382.9B98C3F5; Wed, 19 Aug 2020 11:08:57 +0900 (KST) Received: from KEI (unknown [12.36.155.227]) by epsmtip1.samsung.com (KnoxPortal) with ESMTPA id 20200819020857epsmtip181371babb51b8fd6987480a92a18d0a4~siU5qibAQ0856508565epsmtip1g; Wed, 19 Aug 2020 02:08:57 +0000 (GMT) Date: Wed, 19 Aug 2020 11:01:26 +0900 From: Cho KyongHo To: Christoph Hellwig Cc: Will Deacon , janghyuck.kim@samsung.com, catalin.marinas@arm.com, linux-kernel@vger.kernel.org, hyesoo.yu@samsung.com, iommu@lists.linux-foundation.org, robin.murphy@arm.com, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 1/2] dma-mapping: introduce relaxed version of dma sync Message-ID: <20200819020121.GA70898@KEI> MIME-Version: 1.0 In-Reply-To: <20200818161006.GA25124@infradead.org> User-Agent: Mutt/1.5.24 (2015-08-30) X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFlrKJsWRmVeSWpSXmKPExsWy7bCmme7uTpt4g10tshbvl/UwWpyesIjJ 4m/nBVaLBfutLTbPKbbY9Pgaq8XlXXPYLA5+eMJq0XLH1IHTY828NYwem1doeWxa1cnmsXlJ vcfkG8sZPfq2rGL0+LxJLoA9KscmIzUxJbVIITUvOT8lMy/dVsk7ON453tTMwFDX0NLCXEkh LzE31VbJxSdA1y0zB+gqJYWyxJxSoFBAYnGxkr6dTVF+aUmqQkZ+cYmtUmpBSk6BoWGBXnFi bnFpXrpecn6ulaGBgZEpUGVCTsajF50sBd38FZcnd7A0MC7j6WLk5JAQMJF4e24KaxcjF4eQ wA5GiUWLjzNBOJ8YJR73zGGBcL4xSnz/c5oVpuXRjcVQLXsZJbafWsAMkhASeMgo8fVeKIjN IqAqcWjNXTYQm01AS2L13OOMILaIgKbEreXtzCDNzALvGCVa+i6zgCSEBbwl1qxoZgKxeQU0 JHqnHWOEsAUlTs58AlbDKWAssWreJ6DNHByiAioSrw7Wg8yREOjlkHi4eB4jSFxCwEVi7jZ1 iEOFJV4d38IOYUtJvOxvY4eon84o8W7+ITaIxGZGiW+7BSFsY4lZz9rB9jILZEi0HXvDDjFT WeLILRaIMJ9Ex+G/UGFeiY42IYhOFYmdU6+xwKzq23uDBaLEQ+LvRCFI6Oxkkvj2XnMCo/ws JH/NQrILwtaRWLD7E9ssoG5mAWmJ5f84IExNifW79Bcwsq5iFEstKM5NTy02KjBBjupNjOD0 quWxg3H22w96hxiZOBgPMUpwMCuJ8PbutY4X4k1JrKxKLcqPLyrNSS0+xGgKjKWJzFKiyfnA BJ9XEm9oamRmZmBpamFqZmShJM77zupCnJBAemJJanZqakFqEUwfEwenVANTuP/JY5McNov3 aLXPzuHvPLBDsaX76gPnLVwSgp8tHGckFMlKNLVZRiw+8snK20C7XMXt4D6uLbkaS0KP2Mhz Tvm7cIIHj/Yjk+3nurj+7U6VXMvFcGPJtqqesl0xLO9PSEpK6H5seB33bLp8VhB3Vc3pv9ty c3/bzFwhtEKs5s7lVMXUzk2ZbkvDstMDHq6wylxy9snPWPH7Zm8q5t5QjtXbOql32bJlIdlP /u5aZrlSqCZ534uvm5jXPmzgjp+S94GbIf9e+XkzH7HNmlu+yUfGmXVear1tZRe2mFFMv1At ufsht/brmzu7ObxD/Pb+2Lxh0czm1i+6Ph8/dBwp+LT4kOqnowErPzpNLHdSYinOSDTUYi4q TgQAeJorQzgEAAA= X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFnrDLMWRmVeSWpSXmKPExsWy7bCSnO7OTpt4gxlrDSzeL+thtDg9YRGT xd/OC6wWC/ZbW2yeU2yx6fE1VovLu+awWRz88ITVouWOqQOnx5p5axg9Nq/Q8ti0qpPNY/OS eo/JN5YzevRtWcXo8XmTXAB7FJdNSmpOZllqkb5dAlfG3vaCgtM8FQtnvmFpYPzP2cXIySEh YCLx6MZi1i5GLg4hgd2MEj1N21kgElIS87rXMkHYwhL3W45AFd1nlPhy9zxYgkVAVeLQmrts IDabgJbE6rnHGUFsEQFNiVvL25lBGpgF3jFKtPRdBpsqLOAtsWZFM1gzr4CGRO+0Y4xQq5kk GtqmskAkBCVOznwCZjMDTb3x7yVQAweQLS2x/B8HSJhTwFhi1bxPrCBhUQEViVcH6ycwCs5C 0jwLSfMshOYFjMyrGCVTC4pz03OLDQsM81LL9YoTc4tL89L1kvNzNzGCI0RLcwfj9lUf9A4x MnEwHmKU4GBWEuHt3WsdL8SbklhZlVqUH19UmpNafIhRmoNFSZz3RuHCOCGB9MSS1OzU1ILU IpgsEwenVANTxXSme748B6a+9GfN+Pr4amq1ccLFeqb69pvncl9bl5xjaM/qKjCOdemrkajz f2pT5KoZxnf1YXV1wMwjmxLZb722XfPm0f34rQ8bf1vfbXI8NoNz0Xx9w0nRfO4mh1gyvQzO 73pzfnJS1UXt8Mj3rxQOXo8LERdSDpssmFW/RT0h6+ycOeIRb9etqxZm/Xg69sY9m4a/oR4e DKl8vh/5iwOvJBh1P+HqetMruuLfJquk63OnLP1mvpZtksaEe99u71n7co8Yn9ZET3bNzp9L p7l+vhRX+Tqj7LPxP3FP7fb50VvOXd6sxfs/Yc7Kn9YTMp7tnpRwrP/T21mbfvG06Z6oZZke f9JHtyhO4SKvEktxRqKhFnNRcSIADimrgP8CAAA= X-CMS-MailID: 20200819020857epcas2p1681b773d1393c7c29a8bc61606061922 X-Msg-Generator: CA Content-Type: multipart/mixed; boundary="----wn.C777VfLFf0j4dI6teQ5O7yZ9hP4.it_WB71vmM7CNsG.7=_30f47_" X-Sendblock-Type: AUTO_CONFIDENTIAL CMS-TYPE: 102P DLP-Filter: Pass X-CFilter-Loop: Reflected X-CMS-RootMailID: 20200818075050epcas2p15c780650f5f6b4a54ce731c273d24c98 References: <1597736591-20457-1-git-send-email-pullip.cho@samsung.com> <20200818082852.GA15145@willie-the-truck> <20200818093739.GB191752@KEI> <20200818100756.GA15543@willie-the-truck> <20200818161006.GA25124@infradead.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ------wn.C777VfLFf0j4dI6teQ5O7yZ9hP4.it_WB71vmM7CNsG.7=_30f47_ Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline On Tue, Aug 18, 2020 at 05:10:06PM +0100, Christoph Hellwig wrote: > On Tue, Aug 18, 2020 at 11:07:57AM +0100, Will Deacon wrote: > > > > so I'm not sure > > > > that we should be complicating the implementation like this to try to > > > > make it "fast". > > > > > > > I agree that this patch makes the implementation of dma API a bit more > > > but I don't think this does not impact its complication seriously. > > > > It's death by a thousand cuts; this patch further fragments the architecture > > backends and leads to arm64-specific behaviour which consequently won't get > > well tested by anybody else. Now, it might be worth it, but there's not > > enough information here to make that call. > > So it turns out I misread the series (*cough*, crazy long lines, > *cough*), and it does not actually expose a new API as I thought, but > it still makes a total mess of the internal interface. It turns out > that on the for cpu side we already have arch_sync_dma_for_cpu_all, > which should do all that is needed. We could do the equivalent for > the to device side, but only IFF there really is a major benefit for > something that actually is mainstream and matters. > Indeed, arch_sync_dma_for_cpu_all() is used where the new internal API arch_sync_barrier_for_cpu() should be called. I just thought it is a special hook for MIPS. In the next version of the patch series, I should consider using arch_sync_dma_for_cpu_all() and introducting its 'for_dev' version with some performance data to show the benefit of the change. Thank you for the proposal. KyongHo ------wn.C777VfLFf0j4dI6teQ5O7yZ9hP4.it_WB71vmM7CNsG.7=_30f47_ Content-Type: text/plain; charset="utf-8" ------wn.C777VfLFf0j4dI6teQ5O7yZ9hP4.it_WB71vmM7CNsG.7=_30f47_--