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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY 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 441D0C28CC6 for ; Mon, 3 Jun 2019 16:53:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 24AF027012 for ; Mon, 3 Jun 2019 16:53:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729190AbfFCQxa (ORCPT ); Mon, 3 Jun 2019 12:53:30 -0400 Received: from bhuna.collabora.co.uk ([46.235.227.227]:35274 "EHLO bhuna.collabora.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727376AbfFCQxa (ORCPT ); Mon, 3 Jun 2019 12:53:30 -0400 Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: koike) with ESMTPSA id 48AD327FDB2 Subject: Re: [PATCH v3 5/5] drm: don't block fb changes for async plane updates To: Sean Paul Cc: dri-devel@lists.freedesktop.org, nicholas.kazlauskas@amd.com, andrey.grodzovsky@amd.com, daniel.vetter@ffwll.ch, linux-kernel@vger.kernel.org, Tomasz Figa , boris.brezillon@collabora.com, David Airlie , Sean Paul , kernel@collabora.com, harry.wentland@amd.com, =?UTF-8?Q?St=c3=a9phane_Marchesin?= , stable@vger.kernel.org, Sandy Huang , linux-rockchip@lists.infradead.org, linux-arm-msm@vger.kernel.org, eric@anholt.net, robdclark@gmail.com, amd-gfx@lists.freedesktop.org, =?UTF-8?Q?Heiko_St=c3=bcbner?= , Maarten Lankhorst , Daniel Vetter , freedreno@lists.freedesktop.org, linux-arm-kernel@lists.infradead.org, Maxime Ripard References: <20190314002027.7833-1-helen.koike@collabora.com> <20190314002027.7833-6-helen.koike@collabora.com> <20190507201819.GI17077@art_vandelay> 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 hyRB+/s7b1zkOofUGW5LxUg+wqJXZcOAvjocqSq3VVHcgyxdm+Nv0g9Hdqo8bQHC2KBK86VK vB+R7tfv7NxVhG1sTW3CQ4gZb0ZugIWS32Mnr+V+0pxci7QpV3jrtVp5W2GA5HlXkOyC6C7H Ao7YhogtvFehnlUdG8NrkC3HhCTF8+nb08yGMVI4mMZ9v/KoIXKC6vT0Ykz434ed9Oc9pDow VUqaKi3ey96QczfE4NI029bmtCY4b5fucaB/aVqWYRH98Jh8oIQVwbt+pY7cL5PxS7dQ/Zuz 6yheqDsUGLev1O3E4R8RZ8jPcfCermL0txvoXXIA56t4ZjuHVcWEe2ERhLHFGq5Zw7KC6u12 kJoiZ6WDBYo4Dp+Gd7a81/WsA33Po0j3tk/8BWoiJCrjXzhtRwARAQABtCdIZWxlbiBLb2lr ZSA8aGVsZW4ua29pa2VAY29sbGFib3JhLmNvbT6JAlQEEwEKAD4CGwEFCwkIBwMFFQoJCAsF 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Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/7/19 5:18 PM, Sean Paul wrote: > On Wed, Mar 13, 2019 at 09:20:26PM -0300, Helen Koike wrote: >> In the case of a normal sync update, the preparation of framebuffers (be >> it calling drm_atomic_helper_prepare_planes() or doing setups with >> drm_framebuffer_get()) are performed in the new_state and the respective >> cleanups are performed in the old_state. >> >> In the case of async updates, the preparation is also done in the >> new_state but the cleanups are done in the new_state (because updates >> are performed in place, i.e. in the current state). >> >> The current code blocks async udpates when the fb is changed, turning >> async updates into sync updates, slowing down cursor updates and >> introducing regressions in igt tests with errors of type: >> >> "CRITICAL: completed 97 cursor updated in a period of 30 flips, we >> expect to complete approximately 15360 updates, with the threshold set >> at 7680" >> >> Fb changes in async updates were prevented to avoid the following scenario: >> >> - Async update, oldfb = NULL, newfb = fb1, prepare fb1, cleanup fb1 >> - Async update, oldfb = fb1, newfb = fb2, prepare fb2, cleanup fb2 >> - Non-async commit, oldfb = fb2, newfb = fb1, prepare fb1, cleanup fb2 (wrong) >> Where we have a single call to prepare fb2 but double cleanup call to fb2. >> >> To solve the above problems, instead of blocking async fb changes, we >> place the old framebuffer in the new_state object, so when the code >> performs cleanups in the new_state it will cleanup the old_fb and we >> will have the following scenario instead: >> >> - Async update, oldfb = NULL, newfb = fb1, prepare fb1, no cleanup >> - Async update, oldfb = fb1, newfb = fb2, prepare fb2, cleanup fb1 >> - Non-async commit, oldfb = fb2, newfb = fb1, prepare fb1, cleanup fb2 >> >> Where calls to prepare/cleanup are balanced. >> >> Cc: # v4.14+ > > I'm not convinced this should be cc: stable, seems more in the improvement > category than a bug fix. I'm cc'ing to stable because the commit mentioned below inserted a regression regarding the speed that cursors can be updated. > >> Fixes: 25dc194b34dd ("drm: Block fb changes for async plane updates") >> Suggested-by: Boris Brezillon >> Signed-off-by: Helen Koike >> Reviewed-by: Boris Brezillon >> Reviewed-by: Nicholas Kazlauskas >> >> --- >> Hello, >> >> I added a TODO in drm_atomic_helper_async_commit() regarding doing a >> full state swap(), Boris and Nicholas, let me know if this is ok and if >> I can keep your Reviewed-by tags) >> >> As mentioned in the cover letter, I tested in almost all platforms with >> igt plane_cursor_legacy and kms_cursor_legacy and I didn't see any >> regressions. But I couldn't test on MSM and AMD because I don't have >> the hardware I would appreciate if anyone could help me testing those. >> >> Thanks! >> Helen >> >> Changes in v3: >> - Add Reviewed-by tags >> - Add TODO in drm_atomic_helper_async_commit() >> >> Changes in v2: >> - Change the order of the patch in the series, add this as the last one. >> - Add documentation >> - s/ballanced/balanced >> >> drivers/gpu/drm/drm_atomic_helper.c | 22 ++++++++++++---------- >> include/drm/drm_modeset_helper_vtables.h | 5 +++++ >> 2 files changed, 17 insertions(+), 10 deletions(-) >> >> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c >> index 2453678d1186..de5812c362b5 100644 >> --- a/drivers/gpu/drm/drm_atomic_helper.c >> +++ b/drivers/gpu/drm/drm_atomic_helper.c >> @@ -1608,15 +1608,6 @@ int drm_atomic_helper_async_check(struct drm_device *dev, >> old_plane_state->crtc != new_plane_state->crtc) >> return -EINVAL; >> >> - /* >> - * FIXME: Since prepare_fb and cleanup_fb are always called on >> - * the new_plane_state for async updates we need to block framebuffer >> - * changes. This prevents use of a fb that's been cleaned up and >> - * double cleanups from occuring. >> - */ >> - if (old_plane_state->fb != new_plane_state->fb) >> - return -EINVAL; >> - >> funcs = plane->helper_private; >> if (!funcs->atomic_async_update) >> return -EINVAL; >> @@ -1647,6 +1638,8 @@ EXPORT_SYMBOL(drm_atomic_helper_async_check); >> * drm_atomic_async_check() succeeds. Async commits are not supposed to swap >> * the states like normal sync commits, but just do in-place changes on the >> * current state. >> + * >> + * TODO: Implement full swap instead of doing in-place changes. >> */ >> void drm_atomic_helper_async_commit(struct drm_device *dev, >> struct drm_atomic_state *state) >> @@ -1657,6 +1650,9 @@ void drm_atomic_helper_async_commit(struct drm_device *dev, >> int i; >> >> for_each_new_plane_in_state(state, plane, plane_state, i) { >> + struct drm_framebuffer *new_fb = plane_state->fb; >> + struct drm_framebuffer *old_fb = plane->state->fb; >> + >> funcs = plane->helper_private; >> funcs->atomic_async_update(plane, plane_state); >> >> @@ -1665,11 +1661,17 @@ void drm_atomic_helper_async_commit(struct drm_device *dev, >> * plane->state in-place, make sure at least common >> * properties have been properly updated. >> */ >> - WARN_ON_ONCE(plane->state->fb != plane_state->fb); >> + WARN_ON_ONCE(plane->state->fb != new_fb); >> WARN_ON_ONCE(plane->state->crtc_x != plane_state->crtc_x); >> WARN_ON_ONCE(plane->state->crtc_y != plane_state->crtc_y); >> WARN_ON_ONCE(plane->state->src_x != plane_state->src_x); >> WARN_ON_ONCE(plane->state->src_y != plane_state->src_y); >> + >> + /* >> + * Make sure the FBs have been swapped so that cleanups in the >> + * new_state performs a cleanup in the old FB. >> + */ >> + WARN_ON_ONCE(plane_state->fb != old_fb); >> } >> } >> EXPORT_SYMBOL(drm_atomic_helper_async_commit); >> diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h >> index cfb7be40bed7..ce582e8e8f2f 100644 >> --- a/include/drm/drm_modeset_helper_vtables.h >> +++ b/include/drm/drm_modeset_helper_vtables.h >> @@ -1174,6 +1174,11 @@ struct drm_plane_helper_funcs { >> * current one with the new plane configurations in the new >> * plane_state. >> * >> + * Drivers should also swap the framebuffers between plane state > > Perhaps add "current" before plane state and then after add "(&drm_plane.state)" > so it's more clear what you're referring to here? > >> + * and new_state. This is required because prepare and cleanup calls >> + * are performed on the new_state object, then to cleanup the old >> + * framebuffer, it needs to be placed inside the new_state object. > > I'd change this bit to: > > * This is required since cleanup for async commits is performed on > * the new state, rather than old state like for traditional commits. > * Since we want to give up the reference on the current (old) fb instead > * of our brand new one, swap them in the driver during the async commit. > >> + * >> * FIXME: >> * - It only works for single plane updates >> * - Async Pageflips are not supported yet >> -- >> 2.20.1 >> > Thanks, I'm sending this update in v4. Helen