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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AA16EC433EF for ; Mon, 15 Nov 2021 08:38:55 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 2CD6662F90 for ; Mon, 15 Nov 2021 08:38:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 2CD6662F90 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=daenzer.net Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 8F8F66EAC4; Mon, 15 Nov 2021 08:38:51 +0000 (UTC) Received: from netline-mail3.netline.ch (mail.netline.ch [148.251.143.180]) by gabe.freedesktop.org (Postfix) with ESMTP id 9AE976EAA7; Mon, 15 Nov 2021 08:38:49 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by netline-mail3.netline.ch (Postfix) with ESMTP id 6C3A8202022; Mon, 15 Nov 2021 09:38:48 +0100 (CET) X-Virus-Scanned: Debian amavisd-new at netline-mail3.netline.ch Received: from netline-mail3.netline.ch ([127.0.0.1]) by localhost (netline-mail3.netline.ch [127.0.0.1]) (amavisd-new, port 10024) with LMTP id 4T_6P52zjLa2; Mon, 15 Nov 2021 09:38:48 +0100 (CET) Received: from thor (24.99.2.85.dynamic.wline.res.cust.swisscom.ch [85.2.99.24]) by netline-mail3.netline.ch (Postfix) with ESMTPA id 18A73202021; Mon, 15 Nov 2021 09:38:48 +0100 (CET) Received: from [127.0.0.1] by thor with esmtp (Exim 4.95) (envelope-from ) id 1mmXVn-000S2V-Kh; Mon, 15 Nov 2021 09:38:47 +0100 Message-ID: Date: Mon, 15 Nov 2021 09:38:47 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.3.0 Content-Language: en-CA To: Lang Yu References: <64e70779-7c33-7849-aa29-aeaee4a89005@amd.com> <4ba7e3f8-7956-882a-6888-57e2448b907d@amd.com> <9a5b8470-d02d-71b4-4a89-6d6c32fdfa5d@daenzer.net> <88dfe9b4-e170-2d6b-604b-03af5d57152b@daenzer.net> <735f8781-982b-a09f-32fe-fded0024a587@gmail.com> <58097218-40dd-55fd-32d2-2a299d39230f@daenzer.net> From: =?UTF-8?Q?Michel_D=c3=a4nzer?= Subject: Re: Questions about KMS flip In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: amd-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Discussion list for AMD gfx List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: =?UTF-8?Q?Christian_K=c3=b6nig?= , dri-devel , "Kazlauskas, Nicholas" , amd-gfx list , =?UTF-8?Q?Christian_K=c3=b6nig?= Errors-To: amd-gfx-bounces@lists.freedesktop.org Sender: "amd-gfx" On 2021-11-15 07:41, Lang Yu wrote: > On Fri, Nov 12, 2021 at 05:10:27PM +0100, Michel DDDnzer wrote: >> On 2021-11-12 16:03, Christian König wrote: >>> Am 12.11.21 um 15:30 schrieb Michel Dänzer: >>>> On 2021-11-12 15:29, Michel Dänzer wrote: >>>>> On 2021-11-12 13:47, Christian König wrote: >>>>>> Anyway this unfortunately turned out to be work for Harray and Nicholas. In detail it's about this bug report here: https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugzilla.kernel.org%2Fshow_bug.cgi%3Fid%3D214621&data=04%7C01%7CLang.Yu%40amd.com%7Cca557eab16864ab544a108d9a5f6f288%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637723302338811983%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=9oG6k22BVp%2BkSvRX6uMlGXc6G%2BA5UL0Qy3W5iDTpvzs%3D&reserved=0 >>>>>> >>>>>> Lang was able to reproduce the issue and narrow it down to the pin in amdgpu_display_crtc_page_flip_target(). >>>>>> >>>>>> In other words we somehow have an unbalanced pinning of the scanout buffer in DC. >>>>> DC doesn't use amdgpu_display_crtc_page_flip_target AFAICT. The corresponding pin with DC would be in dm_plane_helper_prepare_fb, paired with the unpin in >>>>> dm_plane_helper_cleanup_fb. >>>>> >>>>> >>>>> With non-DC, the pin in amdgpu_display_crtc_page_flip_target is paired with the unpin in dm_plane_helper_cleanup_fb >>>> This should say amdgpu_display_unpin_work_func. >>> >>> Ah! So that is the classic (e.g. non atomic) path? >> >> Presumably. >> >> >>>>> & dce_v*_crtc_disable. One thing I notice is that the pin is guarded by if (!adev->enable_virtual_display), but the unpins seem unconditional. So could this be about virtual display, and the problem is actually trying to unpin a BO that was never pinned? >>> >>> Nope, my educated guess is rather that we free up the BO before amdgpu_display_unpin_work_func is called. >>> >>> E.g. not pin unbalance, but rather use after free. >> >> amdgpu_display_crtc_page_flip_target calls amdgpu_bo_ref(work->old_abo), and amdgpu_display_unpin_work_func calls amdgpu_bo_unref(&work->old_abo) only after amdgpu_bo_unpin. So what you describe could only happen if there's an imbalance elsewhere such that amdgpu_bo_unref is called more often than amdgpu_bo_ref, or maybe if amdgpu_bo_reserve fails in amdgpu_display_unpin_work_func (in which case the "failed to reserve buffer after flip" error message should appear in dmesg). > > > Actually, each call to amdgpu_display_crtc_page_flip_target() will > > 1, init a work(amdgpu_display_unpin_work_func) to unpin an old buffer > (crtc->primary->fb), the work will be queued in dce_vX_0_pageflip_irq(). > > 2, pin a new buffer, assign it to crtc->primary->fb. But how to unpin it? > Next call. > > The problem is the pinned buffer of last call to > amdgpu_display_crtc_page_flip_target() is not unpinned. It's unpinned in dce_v*_0_crtc_disable. I think I've found the problem though: dce_v*_0_crtc_do_set_base pin the BO from target_fb unconditionally, but unpin the BO from the fb parameter only if it's different from the former. So if they're the same, the BO's pin count is incremented by 1. -- Earthling Michel Dänzer | https://redhat.com Libre software enthusiast | Mesa and Xwayland developer