PCI: Workaround invalid P2P bridge bus numbers (a1c19894) · Commits · 戴 / test

Some firmware fail to properly configure P2P bridges, leaving them with invalid bus numbers. In some cases, this happens on some embedded 4xx boards as the result of the kernel allocating different bus space than the firmware does to host bridges while not setting pcibios_assign_all_busses() for various reasons. In other cases, it can just be bogus firmware. This adds some sanity checking to the PCI probing code. If a bridge is found whose primary bus number doesn't match the bus it's sitting on, or whose secondary bus number not strictly above it's primary bus number, then the bridge bus numbers are deconfigured in the first pass of pci_scan_bridge() to be re-assigned in the second pass. Tested-by:

"Ayman El-Khashab" <AymanE@tanisys.com> Signed-off-by:

Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by:

Jesse Barnes <jbarnes@virtuousgeek.org>

drivers/pci/probe.c

+10 −2

Original line number	Diff line number	Diff line
		@@ -480,19 +480,27 @@ int __devinit pci_scan_bridge(struct pci_bus bus, struct pci_dev dev, int max,
		int is_cardbus = (dev->hdr_type == PCI_HEADER_TYPE_CARDBUS);
		u32 buses, i, j = 0;
		u16 bctl;
		int broken = 0;

		pci_read_config_dword(dev, PCI_PRIMARY_BUS, &buses);

		dev_dbg(&dev->dev, "scanning behind bridge, config %06x, pass %d\n",
		buses & 0xffffff, pass);

		/* Check if setup is sensible at all */
		if (!pass &&
		((buses & 0xff) != bus->number \|\| ((buses >> 8) & 0xff) <= bus->number)) {
		dev_dbg(&dev->dev, "bus configuration invalid, reconfiguring\n");
		broken = 1;
		}

		/* Disable MasterAbortMode during probing to avoid reporting
		of bus errors (in some architectures) */
		pci_read_config_word(dev, PCI_BRIDGE_CONTROL, &bctl);
		pci_write_config_word(dev, PCI_BRIDGE_CONTROL,
		bctl & ~PCI_BRIDGE_CTL_MASTER_ABORT);

		if ((buses & 0xffff00) && !pcibios_assign_all_busses() && !is_cardbus) {
		if ((buses & 0xffff00) && !pcibios_assign_all_busses() && !is_cardbus && !broken) {
		unsigned int cmax, busnr;
		/*
		* Bus already configured by firmware, process it in the first
		@@ -530,7 +538,7 @@ int __devinit pci_scan_bridge(struct pci_bus bus, struct pci_dev dev, int max,
		* do in the second pass.
		*/
		if (!pass) {
		if (pcibios_assign_all_busses())
		if (pcibios_assign_all_busses() \|\| broken)
		/* Temporarily disable forwarding of the
		configuration cycles on all bridges in
		this bus segment to avoid possible

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