From patchwork Thu Nov 30 20:07:40 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: 172092 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:a59:bcd1:0:b0:403:3b70:6f57 with SMTP id r17csp653590vqy; Thu, 30 Nov 2023 12:08:24 -0800 (PST) X-Google-Smtp-Source: AGHT+IENw7T3ZkS3vjAF0wZ78iDeWNCJmK38el12rOre5TPvIpOQqeU31nQ9WklSUmPbaM3Zn8L7 X-Received: by 2002:a17:902:ab94:b0:1cf:b6a7:67a3 with SMTP id f20-20020a170902ab9400b001cfb6a767a3mr18863601plr.56.1701374903954; Thu, 30 Nov 2023 12:08:23 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1701374903; cv=none; d=google.com; s=arc-20160816; b=hfqyS0khhs0N9mRbfaiz9KlUbPkSB8cu7OEagJKjL0IMtkHkHiEPPiR23q4Wh1vz5p xGIHiw0NpTUR2HO43Icjf9DqPc4El1jSKtQcUm5XLq50I+cZvS1J3EioQ7WuCC04aBzV VcePF+H5Nfb7Mh4MOeT86R3N4U9usNlfMHIC8zX/GyuRuaFVnLRuw2sHF+xpOu4Y7Jra y5weSqAOi0Scrh83s2BS6VDXuCSZrhWO+9x2I2s/l5EFTjqZMnlLMNaZEWgi37vVhIF0 UkKTWCURBV/XcvF9BbW8S3TW8f63Ru9boh/IIklrcILDNVhyTmWKB17rF0U4b/F5MnWS qpeg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :message-id:date:subject:cc:to:from:dkim-signature; bh=pyLKFFJL0+QHAkvFUr9epX+zDms0kHGRY+0nNCweE+4=; fh=18fWb0uenUjqkqPHN8BzGUlYdHyPB+vjLzkxaDKnpO0=; b=hotpTXhL6ml1AcUM0L+EgQJqnc2G8IU3hVZNzh3JrJPt8SG96NVPneLZ0u30ELf5uF 42krKGe0O91McTwZHJzPzZuipSJwyZOo6xxk2edLxDNPXbYNANYrzF7WMLnIeEhBUPoI t6IPg80495oG1f3xyeDvSjPp4jZKhdabI14Numc/IgtToI0TZO2bQ1LX2YzfXrRH3E45 fmeBf422hQoe1YCRo+su8Spz+xvlX5Gk5GZJvoSlhInyjr3aL7KZrWwhPrAdWKugMcJZ 5bFZ1jWW2YHDCoANbDJkY3NhX8OTCNO1V/UcZObDyV5VIv4PiTIFGeboD250vVSYG97o g1mw== ARC-Authentication-Results: i=1; mx.google.com; dkim=fail header.i=@igalia.com header.s=20170329 header.b=VRCEDbxy; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:5 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: from groat.vger.email (groat.vger.email. [2620:137:e000::3:5]) by mx.google.com with ESMTPS id f4-20020a170902ce8400b001cfb52d9bf3si1901751plg.438.2023.11.30.12.08.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Nov 2023 12:08:23 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:5 as permitted sender) client-ip=2620:137:e000::3:5; Authentication-Results: mx.google.com; dkim=fail header.i=@igalia.com header.s=20170329 header.b=VRCEDbxy; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:5 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: from out1.vger.email (depot.vger.email [IPv6:2620:137:e000::3:0]) by groat.vger.email (Postfix) with ESMTP id 0D39980DB73C; Thu, 30 Nov 2023 12:08:21 -0800 (PST) X-Virus-Status: Clean X-Virus-Scanned: clamav-milter 0.103.11 at groat.vger.email Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1376596AbjK3UIA (ORCPT + 99 others); Thu, 30 Nov 2023 15:08:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42918 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1376594AbjK3UH7 (ORCPT ); Thu, 30 Nov 2023 15:07:59 -0500 Received: from fanzine2.igalia.com (fanzine.igalia.com [178.60.130.6]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8D93910FC; Thu, 30 Nov 2023 12:08:03 -0800 (PST) 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: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: In-Reply-To:References:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=pyLKFFJL0+QHAkvFUr9epX+zDms0kHGRY+0nNCweE+4=; b=VRCEDbxyM4FF5Dt9ADAKKchvzy K5FxoPzCUxIch4XBRnoCKBVF4kaTMkl00Pi7kuUWTciw8vZwbQr7NOF5IHA9qYSbrkCIANQ/OrjyK pfzIhvTkDb8r72PrdWrTG20n7y9aLnVpk+Zcjf9NT2joLBNPRsg6RrlDomc4WbtGy8Ou1nfIi3LB2 h7rIziMyU2ojrcQ5SCnLKZx9dCLZZDTviZK0GIb9h66ltoLbuhBZdDGzsa6h9Qs4B0bf8PX2lFbRj wDoAQgQaBlB4SsYGXAb25JNXN1c8HjPRH6MKkx78LDf6qTbSvx725N6gmUGtzFUext3qMALJTcxsI LFt/SvWg==; Received: from [191.193.131.178] (helo=steammachine.lan) by fanzine2.igalia.com with esmtpsa (Cipher TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim) id 1r8nKC-008wQ8-W1; Thu, 30 Nov 2023 21:07:53 +0100 From: =?utf-8?q?Andr=C3=A9_Almeida?= To: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Cc: kernel-dev@igalia.com, alexander.deucher@amd.com, christian.koenig@amd.com, Simon Ser , Rob Clark , Pekka Paalanen , daniel@ffwll.ch, Daniel Stone , =?utf-8?b?J01hcmVr?= =?utf-8?b?IE9sxaHDoWsn?= , Dave Airlie , =?utf-8?q?Michel_D=C3=A4nzer?= , Randy Dunlap , Jonathan Corbet , linux-doc@vger.kernel.org, Thomas Zimmermann , Maxime Ripard , Maarten Lankhorst , Pekka Paalanen , =?utf-8?q?Andr=C3=A9_Almeida?= Subject: [PATCH] drm/doc: Define KMS atomic state set Date: Thu, 30 Nov 2023 17:07:40 -0300 Message-ID: <20231130200740.53454-1-andrealmeid@igalia.com> X-Mailer: git-send-email 2.43.0 MIME-Version: 1.0 X-Spam-Status: No, score=-0.6 required=5.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on groat.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (groat.vger.email [0.0.0.0]); Thu, 30 Nov 2023 12:08:21 -0800 (PST) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1784020891184045470 X-GMAIL-MSGID: 1784020891184045470 From: Pekka Paalanen Specify how the atomic state is maintained between userspace and kernel, plus the special case for async flips. Signed-off-by: Pekka Paalanen Signed-off-by: André Almeida Reviewed-by: Bagas Sanjaya --- This is a standalone patch from the following serie, the other patches are already merged: https://lore.kernel.org/lkml/20231122161941.320564-1-andrealmeid@igalia.com/ Documentation/gpu/drm-uapi.rst | 47 ++++++++++++++++++++++++++++++++++ 1 file changed, 47 insertions(+) diff --git a/Documentation/gpu/drm-uapi.rst b/Documentation/gpu/drm-uapi.rst index 370d820be248..d0693f902a5c 100644 --- a/Documentation/gpu/drm-uapi.rst +++ b/Documentation/gpu/drm-uapi.rst @@ -570,3 +570,50 @@ dma-buf interoperability Please see Documentation/userspace-api/dma-buf-alloc-exchange.rst for information on how dma-buf is integrated and exposed within DRM. + +KMS atomic state +================ + +An atomic commit can change multiple KMS properties in an atomic fashion, +without ever applying intermediate or partial state changes. Either the whole +commit succeeds or fails, and it will never be applied partially. This is the +fundamental improvement of the atomic API over the older non-atomic API which is +referred to as the "legacy API". Applying intermediate state could unexpectedly +fail, cause visible glitches, or delay reaching the final state. + +An atomic commit can be flagged with DRM_MODE_ATOMIC_TEST_ONLY, which means the +complete state change is validated but not applied. Userspace should use this +flag to validate any state change before asking to apply it. If validation fails +for any reason, userspace should attempt to fall back to another, perhaps +simpler, final state. This allows userspace to probe for various configurations +without causing visible glitches on screen and without the need to undo a +probing change. + +The changes recorded in an atomic commit apply on top the current KMS state in +the kernel. Hence, the complete new KMS state is the complete old KMS state with +the committed property settings done on top. The kernel will try to avoid +no-operation changes, so it is safe for userspace to send redundant property +settings. However, not every situation allows for no-op changes, due to the +need to acquire locks for some attributes. Userspace needs to be aware that some +redundant information might result in oversynchronization issues. No-operation +changes do not count towards actually needed changes, e.g. setting MODE_ID to a +different blob with identical contents as the current KMS state shall not be a +modeset on its own. As a special exception for VRR needs, explicitly setting +FB_ID to its current value is not a no-op. + +A "modeset" is a change in KMS state that might enable, disable, or temporarily +disrupt the emitted video signal, possibly causing visible glitches on screen. A +modeset may also take considerably more time to complete than other kinds of +changes, and the video sink might also need time to adapt to the new signal +properties. Therefore a modeset must be explicitly allowed with the flag +DRM_MODE_ATOMIC_ALLOW_MODESET. This in combination with +DRM_MODE_ATOMIC_TEST_ONLY allows userspace to determine if a state change is +likely to cause visible disruption on screen and avoid such changes when end +users do not expect them. + +An atomic commit with the flag DRM_MODE_PAGE_FLIP_ASYNC is allowed to +effectively change only the FB_ID property on any planes. No-operation changes +are ignored as always. Changing any other property will cause the commit to be +rejected. Each driver may relax this restriction if they have guarantees that +such property change doesn't cause modesets. Userspace can use TEST_ONLY commits +to query the driver about this.