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, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS 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 AAA13C10F0E for ; Fri, 12 Apr 2019 14:06:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6B50F21872 for ; Fri, 12 Apr 2019 14:06:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727069AbfDLOGa (ORCPT ); Fri, 12 Apr 2019 10:06:30 -0400 Received: from bhuna.collabora.co.uk ([46.235.227.227]:35080 "EHLO bhuna.collabora.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726327AbfDLOG3 (ORCPT ); Fri, 12 Apr 2019 10:06:29 -0400 Received: from [IPv6:2804:431:9718:a5e8:c168:522a:50d5:d06d] (unknown [IPv6:2804:431:9718:a5e8:c168:522a:50d5:d06d]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: koike) by bhuna.collabora.co.uk (Postfix) with ESMTPSA id 1FCE3281156; Fri, 12 Apr 2019 15:06:16 +0100 (BST) Subject: Re: [PATCH v3 2/4] drm/atomic: rename async_{update,check} to amend_{update,check} To: Boris Brezillon Cc: dri-devel@lists.freedesktop.org, David Airlie , dnicoara@chromium.org, daniels@collabora.com, alexandros.frantzis@collabora.com, daniel.vetter@ffwll.ch, linux-kernel@vger.kernel.org, tomasz Figa , tina.zhang@intel.com, Sean Paul , kernel@collabora.com, nicholas.kazlauskas@amd.com, =?UTF-8?Q?St=c3=a9phane_Marchesin?= , Gustavo Padovan , Sean Paul , Sandy Huang , linux-doc@vger.kernel.org, Thomas Zimmermann , Jonathan Corbet , Harry Wentland , Alex Deucher , Bhawanpreet Lakha , "David (ChunMing) Zhou" , Anthony Koo , Russell King , linux-rockchip@lists.infradead.org, =?UTF-8?B?VmlsbGUgU3lyasOkbMOk?= , Rob Clark , =?UTF-8?Q?Heiko_St=c3=bcbner?= , Eric Anholt , Leo Li , linux-arm-msm@vger.kernel.org, =?UTF-8?Q?Christian_K=c3=b6nig?= , linux-arm-kernel@lists.infradead.org, David Francis , Mikita Lipski , amd-gfx@lists.freedesktop.org, Maarten Lankhorst , Maxime Ripard , freedreno@lists.freedesktop.org, Mamta Shukla , Daniel Vetter References: <20190412125827.5877-1-helen.koike@collabora.com> <20190412125827.5877-3-helen.koike@collabora.com> <20190412154957.558e49f8@collabora.com> From: Helen Koike Openpgp: preference=signencrypt Autocrypt: addr=helen.koike@collabora.com; keydata= mQINBFmOMD4BEADb2nC8Oeyvklh+ataw2u/3mrl+hIHL4WSWtii4VxCapl9+zILuxFDrxw1p XgF3cfx7g9taWBrmLE9VEPwJA6MxaVnQuDL3GXxTxO/gqnOFgT3jT+skAt6qMvoWnhgurMGH wRaA3dO4cFrDlLsZIdDywTYcy7V2bou81ItR5Ed6c5UVX7uTTzeiD/tUi8oIf0XN4takyFuV Rf09nOhi24bn9fFN5xWHJooFaFf/k2Y+5UTkofANUp8nn4jhBUrIr6glOtmE0VT4pZMMLT63 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JkgmmesIAw8mpI6EeLmReUJLasz8QkzhZIC7t5rGlQI94GQG3Jg2dC+kpaGWOaT5G4FVMcBj iR1nXfMxENVYnM5ag7mBZyD/kru5W1Uj34L6AFaDMXFPwedSCpzzqUiHb0f+nYkfOodf5xy0 46+3THy/NUS/ZZp/rI4F7Y77+MQPVg7vARfHHX1AxYUKfRVW5j88QUB70txn8Vgi1tDrOr4J eD+xr0CvIGa5lKqgQacQtGkpOpJ8zY4ObSvpNubey/qYUE3DCXD0n2Xxk4muTvqlkFpOYA== Message-ID: Date: Fri, 12 Apr 2019 11:06:13 -0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <20190412154957.558e49f8@collabora.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Boris, On 4/12/19 10:49 AM, Boris Brezillon wrote: > Hi Helen, > > On Fri, 12 Apr 2019 09:58:25 -0300 > Helen Koike wrote: > >> Asynchronous update is the ability change the hw state at any time, not >> only during vblank. >> >> Amend mode is the ability to perform 1000 commits to be applied as soon >> as possible without waiting for 1000 vblanks. >> >> async updates can be seen as amend, but the opposite is not true. >> >> &drm_plane_helper_funcs.atomic_async_{update,check}() was being used by >> drivers to implement amend and not async. So rename them to amend. >> >> Also improve docs explaining the difference. >> >> If asynchronous is required, normal page flip can be performed using >> DRM_MODE_PAGE_FLIP_ASYNC flag. >> >> Signed-off-by: Helen Koike >> >> --- >> Hello, >> >> I would like to officially clarify what async update means by adding it >> in the docs. >> Please correct me if I am wrong, but the current async_{update,check} >> callbacks are being used to do amend (the legacy cursor behavior), i.e. >> to allow 1000 updates without waiting for 1000 vblanks. > > Right now, the semantic of async update is driver dependent. Some > drivers will amend the last commit touching that plane (amend semantic), > others will update the plane buffer immediately which might cause > tearing (async semantic). In my pov, async updates holds the properties of an amend update, so all async updates we have are amend, but the opposite is not true. > >> >> So I would like to clarify this in the docs and rename the current >> callbacks to reflect this behaviour. > > I'm all for this clarification, but I don't think renaming the async > hooks is a good idea, since some drivers will not do real 'amend'. So, > you're changing the name, but it's still confusing :-). > > How about adding new hooks (and/or flags) for the AMEND case, and > keeping the async path untouched. We can then let drivers that > currently implement async as amend implement the amend hooks instead. > Once you've done that, you can hook that up to the legacy cursor update > path so that it first tries one then the other and finally falls back > to a sync update if none of ASYNC/AMEND is possible. I kinda did this (I re-introduced async in the last patch in the series). I know this order is confusing, but as rockchip doesn't implement true async, I would have to do a bunch of modifs at once to keep the commits consistent, but I can re-work on that if it makes things clearer. > >> >> I also see that for real async updates, the flag >> DRM_MODE_PAGE_FLIP_ASYNC can be used in a normal sync update (it is >> already being used by some drivers actually, in the atomic path, not only >> in the legacy page flip, at least is what I understood from >> amdgpu_dm_atomic_commit_tail() implementation). > > Yes, right now, async does not necessarily imply non-block, but > Daniel seemed to think that most users want non-block when they do an > async page flip, so maybe it should be clarified too. users could combine NONBLOCK flag with PAGE_FLIP_ASYNC, no? (we need to add code for it of course). Thanks Helen > > Regards, > > Boris >