From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bmailout1.hostsharing.net (bmailout1.hostsharing.net [83.223.95.100]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 935722EAB61; Tue, 11 Nov 2025 11:09:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=83.223.95.100 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762859349; cv=none; b=QZMtkq+/cJCBKI5pnOc2HUGOclhW66JCEeOUdX6bAax/NsXxLFl1YER8whqg7z2DfqIh0qGG0qmXpxy+agjwwHSM2D8+YSbwKmIAwB9kaHeFzRxZRrtpXvR/ZkMUHKG04DyiP3aoDrxibxSyZ6wb4vIw3G9C54dDxUP23QcVXrE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762859349; c=relaxed/simple; bh=g4qtekS6FGx9+vIKpYeXhIHSaObQ4kXOK4LCHAtTqfA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Fz/KeR3URrw4vRD1/3OJhlYGasQFBeJHybPcJYY3RfOt6+6zXg3PbVxNLgzOs4uIT388qhK5MLGsgzUSM+4ajdA34EEgs1Lqp36V4Wg/1uLB+2vRi0ZNbLZPhcKBtGoplPKRQY3MODYtA3k5tkzhGqAZAUtFaJVpAByZx5+lFPM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=wunner.de; spf=none smtp.mailfrom=h08.hostsharing.net; arc=none smtp.client-ip=83.223.95.100 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=wunner.de Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=h08.hostsharing.net Received: from h08.hostsharing.net (h08.hostsharing.net [IPv6:2a01:37:1000::53df:5f1c:0]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (secp384r1) server-digest SHA384 client-signature ECDSA (secp384r1) client-digest SHA384) (Client CN "*.hostsharing.net", Issuer "GlobalSign GCC R6 AlphaSSL CA 2025" (verified OK)) by bmailout1.hostsharing.net (Postfix) with ESMTPS id 393332C075A7; Tue, 11 Nov 2025 12:08:59 +0100 (CET) Received: by h08.hostsharing.net (Postfix, from userid 100393) id 240131983; Tue, 11 Nov 2025 12:08:59 +0100 (CET) Date: Tue, 11 Nov 2025 12:08:59 +0100 From: Lukas Wunner To: Niklas Cassel Cc: Jingoo Han , Manivannan Sadhasivam , Lorenzo Pieralisi , Krzysztof =?utf-8?Q?Wilczy=C5=3Fski?= , 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> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251111105100.869997-8-cassel@kernel.org> 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). Thanks, Lukas