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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, UNPARSEABLE_RELAY,URIBL_BLOCKED autolearn=unavailable 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 C492BC43381 for ; Wed, 27 Feb 2019 14:34:21 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 91B33213A2 for ; Wed, 27 Feb 2019 14:34:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="kICW3Phn" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 91B33213A2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=mediatek.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Date:To:From:Subject:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=LtsrdwvbkKYaW5IjND4L0on0RaFOGZvBQoIuQQfdC68=; b=kICW3PhnfCl2lc UhAhXlPjykHYYnY4CMnHDeRviSjzo8mklym4t7Eqea6ukQHSvh2tfYTzC1WvVtt0SFpkySpc6D4Je WRbwbYxq+XQr9CsVGAeMwJP8UGC8lOmX+Z9vGU3QfJc/jKc70n0oA+Od6DZBWN1kvqzfR27Uj0nMu zzaRSGYiAOCyFFqAyJHOhY0k6ueX5dVXRwCWc0obNU6jZdL/sjmEs5xcs+LZc5NTVdfFj4Os343i0 wgw+in0cmTUgT1ECX2P18HOD91um4HdjgS9N6wnG/xDgIojoVJRB9+gU2V7rBoTpgBrBnigGJ7qlV 6sxwdyJXBDqepUhG9k2w==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1gz0Hp-0008Ez-82; Wed, 27 Feb 2019 14:34:17 +0000 Received: from mailgw01.mediatek.com ([216.200.240.184]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1gz0Hh-00086a-6K; Wed, 27 Feb 2019 14:34:11 +0000 X-UUID: 855a46618f984e6dabc8a00fb40cf0bb-20190227 X-UUID: 855a46618f984e6dabc8a00fb40cf0bb-20190227 Received: from mtkcas66.mediatek.inc [(172.29.193.44)] by mailgw01.mediatek.com (envelope-from ) (musrelay.mediatek.com ESMTP with TLS) with ESMTP id 1399887059; Wed, 27 Feb 2019 06:33:59 -0800 Received: from MTKMBS31N2.mediatek.inc (172.27.4.87) by MTKMBS62N1.mediatek.inc (172.29.193.41) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Wed, 27 Feb 2019 06:33:57 -0800 Received: from MTKCAS36.mediatek.inc (172.27.4.186) by MTKMBS31N2.mediatek.inc (172.27.4.87) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Wed, 27 Feb 2019 22:33:55 +0800 Received: from [10.17.3.153] (172.27.4.253) by MTKCAS36.mediatek.inc (172.27.4.170) with Microsoft SMTP Server id 15.0.1395.4 via Frontend Transport; Wed, 27 Feb 2019 22:33:54 +0800 Message-ID: <1551278034.17917.52.camel@mhfsdcap03> Subject: Re: [PATCH 03/13] iommu/mediatek: Add probe_defer for smi-larb From: Yong Wu To: Evan Green Date: Wed, 27 Feb 2019 22:33:54 +0800 In-Reply-To: References: <1546318276-18993-1-git-send-email-yong.wu@mediatek.com> <1546318276-18993-4-git-send-email-yong.wu@mediatek.com> X-Mailer: Evolution 3.2.3-0ubuntu6 MIME-Version: 1.0 X-MTK: N X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190227_063409_434447_2056AD9F X-CRM114-Status: GOOD ( 18.83 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: youlin.pei@mediatek.com, "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , Nicolas Boichat , Arnd Bergmann , srv_heupstream@mediatek.com, Greg Kroah-Hartman , Joerg Roedel , Will Deacon , LKML , Tomasz Figa , iommu@lists.linux-foundation.org, Rob Herring , linux-mediatek@lists.infradead.org, Matthias Brugger , yingjoe.chen@mediatek.com, Robin Murphy , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, 2019-02-25 at 15:54 -0800, Evan Green wrote: > On Mon, Dec 31, 2018 at 8:52 PM Yong Wu wrote: > > > > The iommu consumer should use device_link to connect with the > > smi-larb(supplier). then the smi-larb should run before the iommu > > consumer. Here we delay the iommu driver until the smi driver is > > ready, then all the iommu consumer always is after the smi driver. > > > > When there is no this patch, if some consumer drivers run before > > smi-larb, the supplier link_status is DL_DEV_NO_DRIVER(0) in the > > device_link_add, then device_links_driver_bound will use WARN_ON > > to complain that the link_status of supplier is not right. > > > > I don't quite have enough knowledge of device links to figure out if > this is a) the right fix, b) a deficiency in the device_links code, or > c) neither. I can not say more about the device link, But from the MTK iommu point of view, it looks a right fix. As the comment above, we should make sure the probe sequence, SMI-larb should be before MTK IOMMU which need be before iommu-consumer. this patch help SMI-larb always is before MTK_IOMMU. Then if there is no this patchset, what the MTK_IOMMU will happen?. The MTK_IOMMU is subsys_initcall, all the consume only need after the MTK_IOMMU and don't need wait for SMI-larb driver. If some consume run before SMI-larb driver, It also is OK while it don't call mtk_smi_larb_get in this probe.(Of course it will abort if it call this while smi-driver don't probe at that time). the consumer and smi-larb normally are module_init, we can not guarantee the the sequence. it is a potential issue. Some consume know it should wait for SMI-larb like [1], but It don't work. [1] https://elixir.bootlin.com/linux/v5.0-rc1/source/drivers/media/platform/mtk-mdp/mtk_mdp_comp.c#L145 > > Perhaps someone else could chime in on this one. > -Evan > > _______________________________________________ > Linux-mediatek mailing list > Linux-mediatek@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-mediatek _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel