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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 3A9B3CCFA18 for ; Tue, 11 Nov 2025 12:39:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=E10Z3L9fyYhUUJch0+xrz/espL7BMNrV8rNe7+PPsv0=; b=dx52OUm75NT+3sgEpm1r/S4pwL gZf4xN3jxvMIk8tmN2XLWwWrtwOGs8/kgBiqZsFB9KVTS5M35cJgybGscj9qo5X5lvU2KHLrv8eDT Pim5MtJVJ8A6eLGpb8N8L1cetc6AS92of3CVmOqhepgBcT/wgTLvZHMvoN8gdGlxStI+sPwDs0IB7 g7xSJLukD6XwqzunQn+irdCeNKk9QTIPLqkRweFFO9m1TjnJE67SLMsKIPjbzxdn1W95R8sU35mla 8x/IH7VCrZ4lw7HPoMYmJXF8Xw1WxcRWfY29kRTyUXcD3jJQfi6CvWMOwupObWnvY/ng5g68Bk155 m3l5w5Pg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vIneU-00000007BfU-44Eu; Tue, 11 Nov 2025 12:39:14 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vIneT-00000007Bf5-07ob; Tue, 11 Nov 2025 12:39:14 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 5F0BB437FD; Tue, 11 Nov 2025 12:39:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3352DC116B1; Tue, 11 Nov 2025 12:39:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762864752; bh=esQHRI8kjTrLvjtgO/6g3Cn+MJc1AfYjyYOhFVM+O/E=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=fk+Onx+GRKUPG65R/pu9BypCrp20PthfFhqBxaKyGgHDdx2K8PW/r5QQR9wW0c6+N SfuQiE1mjfhOSmfAOLXiz15L0Z5AcoINETlSEnh12THxHFehPq5qemda1a36CLUHOC tAWcDKZi/dz/WuevDyD9iJgh0ADaFRisAyFKnagXwNrFLPw+h7wu2DQvlFE05ZAbql A+HHIDliRyNgdg0EiN9Gd0Ao7GnO2X99d6qsxX2o9r1zdEu2T7TskOR8r/wFaXHhdN tJB8+ppTqEyLLk98RsPj8Acg2FyTi8rt4/bfm3+Crhc5aApsD36p0/2dLQ5FwCEdst L+BI2s47TbA6A== Date: Tue, 11 Nov 2025 13:39:06 +0100 From: Niklas Cassel To: Lukas Wunner Cc: Jingoo Han , Manivannan Sadhasivam , Lorenzo Pieralisi , Krzysztof =?utf-8?B?V2lsY3p577+9P3NraQ==?= , Rob Herring , Bjorn Helgaas , Heiko Stuebner , Shawn Lin , FUKAUMI Naoki , Krishna chaitanya chundru , linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org, linux-arm-msm@vger.kernel.org Subject: Re: [PATCH 0/6] PCI: dwc: Revert Link Up IRQ support Message-ID: References: <20251111105100.869997-8-cassel@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251111_043913_090660_A08698A3 X-CRM114-Status: GOOD ( 19.16 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hello Lukas, On Tue, Nov 11, 2025 at 12:08:59PM +0100, Lukas Wunner wrote: > On Tue, Nov 11, 2025 at 11:51:00AM +0100, Niklas Cassel wrote: > > Revert all patches related to pcie-designware Root Complex Link Up IRQ > > support. > > > > While this fake hotplugging was a nice idea, it has shown that this feature > > does not handle PCIe switches correctly: > [...] > > During the initial scan, PCI core doesn't see the switch and since the Root > > Port is not hot plug capable, the secondary bus number gets assigned as the > > subordinate bus number. This means, the PCI core assumes that only one bus > > will appear behind the Root Port since the Root Port is not hot plug > > capable. > > > > This works perfectly fine for PCIe endpoints connected to the Root Port, > > since they don't extend the bus. However, if a PCIe switch is connected, > > then there is a problem when the downstream busses starts showing up and > > the PCI core doesn't extend the subordinate bus number after initial scan > > during boot. > > In principle it is possible to set the is_hotplug_bridge flag on the > bridge to force allocation of more buses. We've already got a quirk > to set the flag on a Conventional PCI bridge whose hotplug capability > cannot be discovered otherwise (see quirk_hotplug_bridge() in > drivers/pci/quirks.c). While pdev->is_hotplug_bridge was also mentioned by Mani, he seems to prefer a revert + eventual migration to pwrctrl framework: https://lore.kernel.org/linux-pci/4f4wsgf56eublizg63fz6xmdjixesalb2q3rxetphd55jpqqju@zfyzsxfgiyim/ https://lore.kernel.org/linux-pci/2n3wamm3txxc6xbmvf3nnrvaqpgsck3w4a6omxnhex3mqeujib@2tb4svn5d3z6/ Kind regards, Niklas