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Commit a1c19894 authored by Benjamin Herrenschmidt's avatar Benjamin Herrenschmidt Committed by Jesse Barnes
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PCI: Workaround invalid P2P bridge bus numbers 



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: default avatar"Ayman El-Khashab" <AymanE@tanisys.com>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: default avatarJesse Barnes <jbarnes@virtuousgeek.org>
parent 0b8b0dca

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