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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED, USER_AGENT_MUTT 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 117EEC43382 for ; Tue, 25 Sep 2018 11:39:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C2206208D9 for ; Tue, 25 Sep 2018 11:39:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C2206208D9 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=c-sky.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 S1728740AbeIYRqK (ORCPT ); Tue, 25 Sep 2018 13:46:10 -0400 Received: from smtp2200-217.mail.aliyun.com ([121.197.200.217]:45019 "EHLO smtp2200-217.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726435AbeIYRqK (ORCPT ); Tue, 25 Sep 2018 13:46:10 -0400 X-Alimail-AntiSpam: AC=CONTINUE;BC=0.07463478|-1;CH=blue;FP=0|0|0|0|0|-1|-1|-1;HT=e01e01542;MF=ren_guo@c-sky.com;NM=1;PH=DS;RN=14;RT=14;SR=0;TI=SMTPD_---.Cve4qQ8_1537875504; Received: from localhost(mailfrom:ren_guo@c-sky.com fp:SMTPD_---.Cve4qQ8_1537875504) by smtp.aliyun-inc.com(10.147.43.230); Tue, 25 Sep 2018 19:38:25 +0800 Date: Tue, 25 Sep 2018 19:38:24 +0800 From: Guo Ren To: Arnd Bergmann Cc: Thomas Gleixner , Jason Cooper , Marc Zyngier , Rob Herring , Mark Rutland , Rob Herring , Stephen Rothwell , Linux Kernel Mailing List , DTML , linux-arch , c-sky_gcc_upstream@c-sky.com, gnu-csky@mentor.com, Greentime Hu Subject: Re: [PATCH V7 1/2] csky/dma: bugfix dma_sync_for_cpu/device Message-ID: <20180925113824.GA7183@guoren> References: <1ccf1bed89758a5a9b57ac2ce6d11ca898a1b9ae.1537276837.git.ren_guo@c-sky.com> <20180925094601.GA2102@guoren> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 25, 2018 at 11:59:48AM +0200, Arnd Bergmann wrote: > On Tue, Sep 25, 2018 at 11:46 AM Guo Ren wrote: > > > > On Mon, Sep 24, 2018 at 10:38:04PM +0200, Arnd Bergmann wrote: > > > On Tue, Sep 18, 2018 at 3:48 PM Guo Ren wrote: > > > > > > > > ref: https://lkml.org/lkml/2018/5/18/1068 > > > > > > > > map for_cpu for_device unmap > > > > TO_DEV writeback none writeback none > > > > TO_CPU invalidate invalidate* invalidate invalidate* > > > > BIDIR writeback invalidate writeback invalidate > > > > > > > > Signed-off-by: Guo Ren > > > > > > Same comment as for the other patch: Explain why the original > > > version is wrong first. When giving a reference to some other > > > discussion, use the "Link" tag above your Signed-off-by line. > > > To point to a discussion on lkml, lore.kernel.org is the > > > recommended archive, so it would become > > > > > > Link: https://lore.kernel.org/lkml/20180518215548.GH17671@n2100.armlinux.org.uk/ > > Ok, I'll improve the comment: > > > > Fixup dma_mapping error in linux-4.19-rc3, and we must implement all > > DMA_TO_DEVICE/FROM_DEVICE/BIDIRECTIONAL for both sync_dma_for_device/cpu. > > The implementation of arch should follow the following rules: > > > > ... > > That seems ok, but it's better to start with a description of the problem > rather than the 'Fixup dma_mapping error in linux-4.19-rc3' part. > I would write this like: > > | The arch_sync_dma_for_cpu()/arch_sync_dma_for_device() > | implementation is broken for some combinations that end up > | in a BUG() instead of performing the necessary flushes. > | > | The implementation of arch should follow the following rules: > | ... > > The imperative 'Fix up dma_mapping error ...' is what belongs > into the subject line, and is ideally revisited at the end of the > changelog comment if you want to add more detail about what > you do. Nice tips, Thx. I'll continue to improve my comments. Best Regards Guo Ren