From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2583A606A33B for ; Sat, 14 Nov 2026 02:02:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=SawnGC/s Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id D211B10ECFE; Sat, 14 Nov 2026 02:02:52 +0000 (UTC) Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by gabe.freedesktop.org (Postfix) with ESMTPS id 2ED7C10ECFE; Sat, 14 Nov 2026 02:02:47 +0000 (UTC) Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id D641740AA4; Sat, 14 Nov 2026 02:02:46 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 870931F000C4; Sat, 14 Nov 2026 02:02:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794621766; bh=/DAXMH/Xlsgy1PzaYwQSHGmCTzCBvTt0IXXJ5Hk5Yec=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=SawnGC/szUbaGxjN6TnzEF9x444/N0/4LO2uGs7QkA4DQ0C5suI6C01vrVDLblXHF +VLakOKiU+8G29RrzPEoEvWw9chCwZHC6xF5xAjpbfGBJwHGN37m/jLmPhjVx384ZE vhIidoKKOPUEeLKyhXHJMc3+8eEJBSmWXiP1qC09TwOzkS9Yfmh3TWG1piNL/zNlWt uQQuqVHHlFPatH0Sfnopc77KTw51xO+P24KO7eMQWv/hcuV7S1jfZW59qsN4Pu+w9u NdBHJpy/dQAp8DpMyhhpkIiHTmIWvmAhL7SOt7dEwe+Wdv1baykMWTS3B+cXgRCaW6 CTOetkKmMbgXg== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH 5/7] drm/i915: Arm joined pipes within one vblank evasion for VRR To: ElXreno , intel-gfx@lists.freedesktop.org, intel-xe@lists.freedesktop.org Cc: dri-devel@lists.freedesktop.org In-Reply-To: <20261114014335.2132756-6-elxreno@gmail.com> References: <20261114014335.2132756-1-elxreno@gmail.com> <20261114014335.2132756-6-elxreno@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Sat, 14 Nov 2026 02:02:46 +0000 X-BeenThere: intel-xe@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel Xe graphics driver List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: sashiko-reviews@lists.linux.dev Sender: "Intel-xe" X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 X-Archived-By: Thank you for your contribution! Sashiko AI review found 1 potential issue to consider: - [High] drm/i915: Signed-off-by trailer uses handle ElXreno instead of real name -- commit fc87993e7c0d725b8ec9527a36ed996a89438f35 Author: ElXreno > drm/i915: Arm joined pipes within one vblank evasion for VRR > > All joined pipes run off the transcoder of the primary, so one vblank > latches every one of them. On the MMIO path each pipe nevertheless > goes through its own intel_pipe_update_start()/intel_pipe_update_end() > critical section, one pipe after another. When the vblank falls > between two of them the earlier pipe latches its new state a frame > ahead of the later one, and for that frame the halves of the screen > come from different frames. > > With VRR that gets worse, as the commit ends the frame itself: the > push at the end of the primary's section latches whatever has been > armed by then. Commit the joined pipes together when VRR is in use: > do the vblank evasion once, on the primary, arm all of them inside > that critical section and let the primary send the push at its end. > The evasion accounting, the trace events and the atomic update > failure check then run once as well, for the primary. > > Armed this way the critical section takes 15 us on average for two > pipes on Arrow Lake (71983 commits at 240 fps: 71918 under 30 us, 16 > between 30 and 60 us, 49 between 60 and 188 us), against the 100 us > the evasion allows for. The window is not scaled with the number of > pipes. The 49 are single MMIO writes that stall, not more work: the > instruction count is that of an ordinary section, the CPU stays in > C0, there is no SMI or NMI, and the register differs from case to > case. The per pipe sections of the same mode without VRR and with > the DSB turned off show the same stalls (15 of 72002 sections over > 60 us), so they do not come from arming two pipes in one section. > None of them ran into a vblank. > > The per pipe sequence is kept where the critical section has per > pipe work attached or the pipes need sequencing against others: > modesets, the atomic fallback of a legacy cursor update, async flips, > commits that need the vblank worker for the LUT load and commits that > change the DDB allocation of a joined pipe. The vblank worker is > needed on the platforms without double buffered LUTs, when a colour > update or a fastset has LUTs to load that can neither be preloaded > nor be left to a colour DSB. Commits that go through the DSB or the > flip queue are not affected, and neither is the commit sequence of a > joined configuration without VRR. The latter has the same race > against the fixed vblank, it is left alone only to keep this change > to the case that can be tested with it. > > On the platforms with double buffered LUTs there is no vblank worker. > Where no colour DSB is used the LUTs are loaded with MMIO inside the > critical section, which here is the joined one and then loads them > for all joined pipes. I have no such hardware and have not tested > that. > > No functional change yet, VRR is not allowed with the joiner. > > Signed-off-by: ElXreno [Severity: High] The Author field and Signed-off-by trailer use a single-word handle (ElXreno) instead of a real full name. Per Documentation/process/submitting-patches.rst, patches must be signed off using a known identity and real full name rather than a pseudonym or handle. --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261114014335.2132= 756-1-elxreno@gmail.com?part=3D5