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=-4.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 8AB11C43381 for ; Wed, 27 Feb 2019 14:34:33 +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 59EAE213A2 for ; Wed, 27 Feb 2019 14:34:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="B52QhC9K" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 59EAE213A2 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=kjTTfVUdDd48gT6RHB7JrHvzfiHOuDfNZWjqqxtn16M=; b=B52QhC9K0lpbHg J5J/s2TiHVZVOgQYlPJUvQ3ZeVGfB/6RCvxBoyQw54Xh8GpX+nlD5ZdV6GL40I8ZRHo/Afu3pD8nU niP4/LloxBOqQ+PLNnKrtOVwz9drn5RrGLQpeu1J58cZuanbqd9UjOkNy3XNR4m0KIskqCDHmfR37 53PwuFUU3KF3IRjzGJiVNEHcd2L6OdskMgF3aNe9kP46pNA3sZVD0VAjzP+APyf4DIWePgvlrVtgZ wjTWw+8weI4Y1DW5goChCQdwbKMMkUGOimByKDk9EnjmvShkEH65MKMm8to9+JTzE61mzgCdiZuYC X1fCE3Cc+to1HtPPrA/Q==; 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 1gz0I1-0008Uw-Ti; Wed, 27 Feb 2019 14:34:29 +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-00087y-6D; Wed, 27 Feb 2019 14:34:13 +0000 X-UUID: 1456cfdddb034b519e92eb9dee2f20cb-20190227 X-UUID: 1456cfdddb034b519e92eb9dee2f20cb-20190227 Received: from mtkcas67.mediatek.inc [(172.29.193.45)] by mailgw01.mediatek.com (envelope-from ) (musrelay.mediatek.com ESMTP with TLS) with ESMTP id 466098291; Wed, 27 Feb 2019 06:33:24 -0800 Received: from MTKMBS31N1.mediatek.inc (172.27.4.69) by MTKMBS62DR.mediatek.inc (172.29.94.18) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Wed, 27 Feb 2019 06:33:22 -0800 Received: from MTKCAS36.mediatek.inc (172.27.4.186) by MTKMBS31N1.mediatek.inc (172.27.4.69) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Wed, 27 Feb 2019 22:33:20 +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 22:33:20 +0800 Message-ID: <1551278000.17917.50.camel@mhfsdcap03> Subject: Re: [PATCH 02/13] driver core: Remove the link if there is no driver with AUTO flag From: Yong Wu To: Evan Green Date: Wed, 27 Feb 2019 22:33:20 +0800 In-Reply-To: References: <1546318276-18993-1-git-send-email-yong.wu@mediatek.com> <1546318276-18993-3-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_551402_89941FC3 X-CRM114-Status: GOOD ( 24.24 ) 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 15:53 -0800, Evan Green wrote: > On Mon, Dec 31, 2018 at 8:52 PM Yong Wu wrote: > > > > DL_FLAG_AUTOREMOVE_CONSUMER/SUPPLIER means "Remove the link > > automatically on consumer/supplier driver unbind", that means we should > > remove whole the device_link when there is no this driver no matter what > > the ref_count of the link is. > > > > CC: Greg Kroah-Hartman > > Signed-off-by: Yong Wu > > --- > > The ref_count of our device_link normally is over 1. When the consumer > > device driver is removed, whole the device_link should be removed. > > Thus, I add this patch. > > --- > > I will admit to reading about device links for the first time while > reviewing this patch, but I don't really get this. Why use a kref at > all if we're just going to ignore its value? For instance, I see that > if you call device_link_add() with the same supplier and consumer, it > uses the kref to return the same link. That machinery is broken with > your change. Although I don't see any uses of it, you might also > expect a supplier or consumer could do a kref_get() on the link it got > back from device_link_add(), and have a reasonable expectation that > the link wouldn't be freed out from under it. This would also be > broken. > > Can you explain why your device_links normally have a reference count > >1, I use device link between the smi-larb device and the iommu-consumer device. Take a example, smi-larb1 have 4 VDEC ports. From 4/13 in this patchset, we use device_link to link the VDEC device and the smi-larb1 device in the function(mtk_iommu_config). since there are 4 ports, it will call device_link_add 4 times. > > and why those additional references can't be cleaned up in an > orderly fashion? If the iommu-consume device(like VDEC above) is removed, It should enter device_links_driver_cleanup which only ref_put one time. I guess whole the link should be removed at that time. > > (To be honest, I don't really understand the case for the AUTOREMOVE > flags at all. Is there some case where the party that set up the link > can't tear it down? Or is this a way to devm_ify the link, where devm > itself doesn't work because the links themselves stall out that > mechanism?) _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel