From patchwork Sat Jul 1 02:09:17 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Andr=C3=A9_Almeida?= X-Patchwork-Id: 13298858 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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 83FAEEB64DA for ; Sat, 1 Jul 2023 02:10:11 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id D483B10E52E; Sat, 1 Jul 2023 02:10:02 +0000 (UTC) Received: from fanzine2.igalia.com (fanzine2.igalia.com [213.97.179.56]) by gabe.freedesktop.org (Postfix) with ESMTPS id B80DF10E530; Sat, 1 Jul 2023 02:09:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Transfer-Encoding:Content-Type:MIME-Version:References: In-Reply-To:Message-ID:Date:Subject:Cc:To:From:Sender:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=FpvV1NRn92NjSFc/aa9HU0kB1fj/LcwCHP8r7t79LKQ=; b=IQwSBaK4dtvffDRp6/HaKl/E7a HJgIluzVyRfp+1nipl9ZO4ikcNp8vPJyIiK/sZ+AWWQz+fEHLF82HpYZdnE/xq61NQ0xOcAkPXuhj pNuMDYbZBfQX4QF3DdXJRehvlT1FOK1ExMYnBSGJvkYGAeE+wqpoqi7VxqUovfVXj7uiUZRvZ7oj+ HIgVNImcyhMGUOTsesmF9Nc19mBFj+GqABzhb0pwSEHz3Udeit2RPm1/3ygDq4s42EMG4D4FvKMjA KYl6+k6jm1dmt0Z+IHtvyZSQP2YpdRPA/xy2zERwziURYskIVdOjutkBqjj87mWiK5IG4ArTQ9aVz oswa/ALg==; Received: from [187.74.70.209] (helo=steammachine.lan) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim) id 1qFQ3g-006abr-5T; Sat, 01 Jul 2023 04:09:56 +0200 From: =?utf-8?q?Andr=C3=A9_Almeida?= To: dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org, wayland-devel@lists.freedesktop.org Subject: [PATCH v4 6/6] drm/doc: Define KMS atomic state set Date: Fri, 30 Jun 2023 23:09:17 -0300 Message-ID: <20230701020917.143394-7-andrealmeid@igalia.com> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230701020917.143394-1-andrealmeid@igalia.com> References: <20230701020917.143394-1-andrealmeid@igalia.com> MIME-Version: 1.0 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: pierre-eric.pelloux-prayer@amd.com, =?utf-8?q?Andr=C3=A9_Almeida?= , =?utf-8?b?J01hcmVr?= =?utf-8?b?IE9sxaHDoWsn?= , =?utf-8?q?Michel_D=C3=A4nzer?= , Italo Nicola , Randy Dunlap , Pekka Paalanen , hwentlan@amd.com, kernel-dev@igalia.com, alexander.deucher@amd.com, christian.koenig@amd.com, joshua@froggi.es Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Specify how the atomic state is maintained between userspace and kernel, plus the special case for async flips. Signed-off-by: André Almeida Signed-off-by: Pekka Paalanen --- v4: new patch --- Documentation/gpu/drm-uapi.rst | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/Documentation/gpu/drm-uapi.rst b/Documentation/gpu/drm-uapi.rst index 65fb3036a580..5464376051cc 100644 --- a/Documentation/gpu/drm-uapi.rst +++ b/Documentation/gpu/drm-uapi.rst @@ -486,3 +486,22 @@ and the CRTC index is its position in this array. .. kernel-doc:: include/uapi/drm/drm_mode.h :internal: + +KMS atomic state +================ + +If a userspace using the DRM atomic API would like to change the modeset, it +needs to do in an atomic way, changing all desired properties in a single +commit. Following commits may contain the same properties again, as if they were +new. The kernel can then judge if those properties requires modesetting and real +changes, or it's just the same state as before. In summary, userspace commits do +not need to set the minimal state as possible and can commit redundant +information, and the kernel will ignore it. + +An observation must be made for atomic operations with DRM_MODE_PAGE_FLIP_ASYNC. +In such scenarios properties values can be sent, but the if they change +something, the kernel will reject the flip. This is done because property +changes can lead to modesetting, that would defeat the goal of flipping as fast +as possible. The only exceptions are the framebuffer ID to be flipped to and +mode IDs changes, which could be referring to an identical mode, thus not +requiring modeset.