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=-3.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no 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 54CAFC433E0 for ; Thu, 11 Feb 2021 16:55:36 +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 76BD564DE1 for ; Thu, 11 Feb 2021 16:55:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 76BD564DE1 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=intel-gfx-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id F40866E453; Thu, 11 Feb 2021 16:55:32 +0000 (UTC) Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by gabe.freedesktop.org (Postfix) with ESMTPS id 06E496E453; Thu, 11 Feb 2021 16:55:31 +0000 (UTC) IronPort-SDR: 3Ywd9xXDHAIFcZLZP5kH7jzudLRdNxDNzWuX7vHMz3sA6N4f1C2u5Wb56AYTpY0fnkkQMYH/zT dcMQqGoUFThw== X-IronPort-AV: E=McAfee;i="6000,8403,9892"; a="182408771" X-IronPort-AV: E=Sophos;i="5.81,170,1610438400"; d="scan'208";a="182408771" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Feb 2021 08:55:31 -0800 IronPort-SDR: +Qt7brR7Gm5axvPagUwZb1vGE9NQw/aVMkXLj0md2jPMa20eJsg53y+DLrN+k5Zi/bIx8jAzWk /SS26zQATq1Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.81,170,1610438400"; d="scan'208";a="437215452" Received: from stinkbox.fi.intel.com (HELO stinkbox) ([10.237.72.171]) by orsmga001.jf.intel.com with SMTP; 11 Feb 2021 08:55:28 -0800 Received: by stinkbox (sSMTP sendmail emulation); Thu, 11 Feb 2021 18:55:27 +0200 Date: Thu, 11 Feb 2021 18:55:27 +0200 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Daniel Stone Message-ID: References: <20210210001401.463-1-manasi.d.navare@intel.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Patchwork-Hint: comment Subject: Re: [Intel-gfx] [PATCH] Revert "drm/atomic: document and enforce rules around "spurious" EBUSY" X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Simon Ser , intel-gfx , dri-devel , Daniel Vetter Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Thu, Feb 11, 2021 at 04:14:02PM +0000, Daniel Stone wrote: > On Wed, 10 Feb 2021 at 15:07, Ville Syrj=E4l=E4 > wrote: > > On Wed, Feb 10, 2021 at 01:38:45PM +0000, Simon Ser wrote: > > > The WARN_ON only happens if allow_modeset =3D=3D false. If allow_mode= set =3D=3D true, > > > then the driver is allowed to steal an unrelated pipe. > > > > > > Maybe i915 is stealing a pipe without allow_modeset? > > > > No. All page flips etc. will have to get split up internally > > between multiple crtcs. > = > I think this is the salient point. > = > > So I think there's basically three options: > > a) massive rewrite of i915 to bypass even more of drm_atomic stuff > > b) allow i915 to silence that warning, which opens up the question > > whether the warn is doing any good if it can just be bypassed > > c) nuke the warning entirely > > > > a) is not going to happen, and it would any way allow i915 to > > do things any which way it wants without tripping the warn, > > rendering the warn entirely toothless. > > > > Hmm. Maybe there is a d) which would be to ignore all crtcs > > that are not logically enabled in the warn? Not sure if that > > could allow something to slit through that people want it to > > catch? > = > So from what I understand, if I enable CRTC 44 and the driver > magically decides to split it up as a 'big-joiner' output, it will > also steal CRTC 50 to work as the other half of the output. Then if I > attach plane 47 to CRTC 44, posting a FB to plane 47 will result in me > getting atomic completion events for both CRTC 44 and CRTC 50? > = > That's not OK from a userspace perspective. If you want to do magic to > create the illusion of a single CRTC, then that magic needs to be > consistent. At the moment it's the worst kind of magic: it does > implicit things under the hood for you, but then leaks all of the > behind-the-scenes detail into userspace. > = > Continuing with that would force us all to just ignore whatever events > we see, because we can't reason about what they may be or why they're > generated. Which doesn't allow for any kind of best practice in > userspace. You should only get externally visibile events for stuff in your request. Or at least if that's not the case then the atomic code is already bork regardless of bigjoiner. -- = Ville Syrj=E4l=E4 Intel _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx