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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 34439C169C4 for ; Wed, 6 Feb 2019 23:51:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0123A218AF for ; Wed, 6 Feb 2019 23:51:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726549AbfBFXv3 (ORCPT ); Wed, 6 Feb 2019 18:51:29 -0500 Received: from anholt.net ([50.246.234.109]:52416 "EHLO anholt.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726161AbfBFXv2 (ORCPT ); Wed, 6 Feb 2019 18:51:28 -0500 Received: from localhost (localhost [127.0.0.1]) by anholt.net (Postfix) with ESMTP id 41EBF10A2BF3; Wed, 6 Feb 2019 15:51:28 -0800 (PST) X-Virus-Scanned: Debian amavisd-new at anholt.net Received: from anholt.net ([127.0.0.1]) by localhost (kingsolver.anholt.net [127.0.0.1]) (amavisd-new, port 10024) with LMTP id YpGqCJs-K-s6; Wed, 6 Feb 2019 15:51:27 -0800 (PST) Received: from eliezer.anholt.net (localhost [127.0.0.1]) by anholt.net (Postfix) with ESMTP id 10AB410A282F; Wed, 6 Feb 2019 15:51:27 -0800 (PST) Received: by eliezer.anholt.net (Postfix, from userid 1000) id 9E5772FE464C; Wed, 6 Feb 2019 15:51:26 -0800 (PST) From: Eric Anholt To: Paul Kocialkowski , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Cc: David Airlie , Daniel Vetter , Maxime Ripard , Thomas Petazzoni , Eben Upton , Paul Kocialkowski Subject: Re: [PATCH v4 3/4] drm/vc4: Detect and ignore underruns caused by out-of-sync dlists In-Reply-To: <20190206144906.24304-4-paul.kocialkowski@bootlin.com> References: <20190206144906.24304-1-paul.kocialkowski@bootlin.com> <20190206144906.24304-4-paul.kocialkowski@bootlin.com> User-Agent: Notmuch/0.22.2+1~gb0bcfaa (http://notmuchmail.org) Emacs/25.2.2 (x86_64-pc-linux-gnu) Date: Wed, 06 Feb 2019 15:51:26 -0800 Message-ID: <875ztwlblt.fsf@anholt.net> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="=-=-="; micalg=pgp-sha512; protocol="application/pgp-signature" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --=-=-= Content-Type: text/plain Paul Kocialkowski writes: > When the pipeline is reconfigured with a different mode, changes take > effect immediately for the CRTC and encoder while the HVS takes some > time to switch the active display list. This results in a period of > time where the pipeline is out of sync, that is very likely to cause > an underrun to be reported. Because the underrun is not related to the > new configuration, reporting it to userspace is a false positive. This seems like a serious issue. How are we enabling a CRTC with the corresponding HVS still scanning out old contents? Did we need to wait for HVS to finish its old frame when we turned off the CRTC, so it's ready to receive the START when it's been set up with the new dlist and the CRTC is turned back on? Or maybe do some sort of reset of that dlist when a crtc is being enabled? If we can't sort that out, it feels to me like we should be enabling the interrupts from the flip_done path (when we know that the HVS is scanning out the new frame) instead of trying to mitigate enabling them too early. --=-=-= Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEE/JuuFDWp9/ZkuCBXtdYpNtH8nugFAlxbcv4ACgkQtdYpNtH8 nuiTkhAAoKL/4v+X/hB+t3PxDjzBWduI0qDjJKwgKHROEBW2HTrWNd/J71r9+6P4 SSVRoqvFE05GbxX0UxibpcjKpTScfBwhC24Ofkl3FYfNJM+R0HV0VQw7DuUCIQjR KoZ96MgAfeCy72lq0RmDLlXOZLh/DgUauWeN8VUVmT2G+TSpvB00ImU0sv4ZuIZB sFJ59q1JFIPyJs/E3M6K/gtcpHiOvFwakjPDEOPlyFht3+G9PDatXepakHmtA1FK ybx1oid23GMx6Dtd/EAvHPdSPIb7jNlEWvs5nJhlDnWgHnO7Oi+wrb7EdWh/eCyP 0i5dl+7uTdo/MfjIrIGBbViwkgrS5uO8WMHYr9DojqhGIriQ76mEGDxeecrwK8Sm USXtMvClXmMxqskAZCo74zVGC8vg76LAqMffRZT06k54jzTr4XpErmjBe+r/uJ84 SRdWK5z0EXkxREEPXPkFdAVdAxAApqVVbS9o1zfNiYu09CxZwJ5DIOjulXCcJBvX VXvSnyTY6XZs28ScUFIymVH/tlKmqCPgqoiNnz/mP7Km/dgBJr1d5PrnoX82eB3+ Ylp41b44xSuRR8uK/b0UNjneFiFU70gI14G9+G4NYAeF3l67luoNpyvzJ7XTf7Ak TJiDv885cez3w88ShN1klKVx7KjoM9OAHD7SySyh0aGhkdbPVzc= =uaei -----END PGP SIGNATURE----- --=-=-=--