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Tue, 15 Sep 2026 03:26:40 -0700 (PDT) From: Andrea della Porta X-Google-Original-From: Andrea della Porta Date: Tue, 15 Sep 2026 12:30:17 +0200 To: Angel J Cc: Andrea della Porta , "linux-pci@vger.kernel.org" , "regressions@lists.linux.dev" , "stable@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "devicetree@vger.kernel.org" , "linux-rpi-kernel@lists.infradead.org" , "helgaas@kernel.org" , "robh@kernel.org" , "florian.fainelli@broadcom.com" Subject: Re: [REGRESSION] PCI: Dynamic OF node creation hangs on invalid bridge configuration Message-ID: References: Precedence: bulk X-Mailing-List: devicetree@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: Hi Angel, On 23:28 Mon 14 Sep , Angel J wrote: > Ok, here it is... > > I tested this quirk on Linux 6.18.44 with CONFIG_PCI_DYNAMIC_OF_NODES=y, > and it boots without either OF fix. The diff below omits the test logging. > > PCI_FIXUP_HEADER runs after the resources have been parsed using the > original header type, and changing hdr_type also affects configuration > restore. I don't know enough about this part of PCI to judge whether > that's safe, so I'll wait for your advice before submitting it as a patch. Thanks you for your submission! LGTM. Maybe you can play, if you don't already, with pci=realloc,assign-busses kernel cmdline options and writing in remove/rescan under /sys/bus/pci/* (watch out: this could kill your system). But better to ask for opinions from PCI experts. Thanks, Andrea > > Thanks, > Angel J > > diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c > index de9bbccda..57df88a38 100644 > --- a/drivers/pci/quirks.c > +++ b/drivers/pci/quirks.c > @@ -291,6 +291,22 @@ static int __init pci_apply_final_quirks(void) > } > fs_initcall_sync(pci_apply_final_quirks); > > > +/* > + * On the Dell XPS 8940, 8086:4c43 reports a PCI-to-PCI bridge but has no > + * downstream bus. Use host-bridge class and a normal header so that > + * pci_is_bridge() does not send it through bridge scanning. > + */ > +static void quirk_intel_4c43_host_bridge(struct pci_dev *dev) > +{ > + if ((dev->class >> 8) != PCI_CLASS_BRIDGE_PCI || > + dev->hdr_type != PCI_HEADER_TYPE_BRIDGE) > + return; > + > + dev->class = (PCI_CLASS_BRIDGE_HOST << 8) | (dev->class & 0xff); > + dev->hdr_type = PCI_HEADER_TYPE_NORMAL; > +} > +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x4c43, quirk_intel_4c43_host_bridge); > + > /* > * Decoding should be disabled for a PCI device during BAR sizing to avoid > * conflict. But doing so may cause problems on host bridge and perhaps other