PCI: Do not use bus number zero from EA capability (73884a70) · Commits · 戴 / test

As per PCIe r5.0, sec 7.8.5.2, fixed bus numbers of a bridge must be zero when no function that uses EA is located behind it. Hence, if EA supplies bus numbers of zero, assign bus numbers normally. A secondary bus can never have a bus number of zero, so setting a bridge's Secondary Bus Number to zero makes downstream devices unreachable. [bhelgaas: retain bool return value so "zero is invalid" logic is local] Fixes: ("PCI: Assign bus numbers present in EA capability for bridges") Link: https://lore.kernel.org/r/1572850664-9861-1-git-send-email-sundeep.lkml@gmail.com Signed-off-by:

Subbaraya Sundeep <sbhatta@marvell.com> Signed-off-by:

Bjorn Helgaas <bhelgaas@google.com> Cc: stable@vger.kernel.org # v5.2+

drivers/pci/probe.c

+11 −5

Original line number	Diff line number	Diff line
		@@ -1090,14 +1090,15 @@ static unsigned int pci_scan_child_bus_extend(struct pci_bus *bus,
		* @sec: updated with secondary bus number from EA
		* @sub: updated with subordinate bus number from EA
		*
		* If @dev is a bridge with EA capability, update @sec and @sub with
		* fixed bus numbers from the capability and return true. Otherwise,
		* return false.
		* If @dev is a bridge with EA capability that specifies valid secondary
		* and subordinate bus numbers, return true with the bus numbers in @sec
		* and @sub. Otherwise return false.
		*/
		static bool pci_ea_fixed_busnrs(struct pci_dev dev, u8 sec, u8 *sub)
		{
		int ea, offset;
		u32 dw;
		u8 ea_sec, ea_sub;

		if (dev->hdr_type != PCI_HEADER_TYPE_BRIDGE)
		return false;
		@@ -1109,8 +1110,13 @@ static bool pci_ea_fixed_busnrs(struct pci_dev dev, u8 sec, u8 *sub)

		offset = ea + PCI_EA_FIRST_ENT;
		pci_read_config_dword(dev, offset, &dw);
		*sec = dw & PCI_EA_SEC_BUS_MASK;
		*sub = (dw & PCI_EA_SUB_BUS_MASK) >> PCI_EA_SUB_BUS_SHIFT;
		ea_sec = dw & PCI_EA_SEC_BUS_MASK;
		ea_sub = (dw & PCI_EA_SUB_BUS_MASK) >> PCI_EA_SUB_BUS_SHIFT;
		if (ea_sec == 0 \|\| ea_sub < ea_sec)
		return false;

		*sec = ea_sec;
		*sub = ea_sub;
		return true;
		}

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