PCI/ASPM: Handle PCI-to-PCIe bridges as roots of PCIe hierarchies

In a struct pcie_link_state, link->root points to the pcie_link_state of
the root of the PCIe hierarchy.  For the topmost link, this points to
itself (link->root = link).  For others, we copy the pointer from the
parent (link->root = link->parent->root).

Previously we recognized that Root Ports originated PCIe hierarchies, but
we treated PCI/PCI-X to PCIe Bridges as being in the middle of the
hierarchy, and when we tried to copy the pointer from link->parent->root,
there was no parent, and we dereferenced a NULL pointer:

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000090
  IP: [<ffffffff9e424350>] pcie_aspm_init_link_state+0x170/0x820

Recognize that PCI/PCI-X to PCIe Bridges originate PCIe hierarchies just
like Root Ports do, so link->root for these devices should also point to
itself.

Fixes: 51ebfc92b72b ("PCI: Enumerate switches below PCI-to-PCIe bridges")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=193411
Link: https://bugzilla.opensuse.org/show_bug.cgi?id=1022181
Tested-by: lists@ssl-mail.com
Tested-by: Jayachandran C. <jnair@caviumnetworks.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: stable@vger.kernel.org	# v4.2+

path: root/drivers/usb/host/pci-quirks.h

#ifndef __LINUX_USB_PCI_QUIRKS_H
#define __LINUX_USB_PCI_QUIRKS_H

#ifdef CONFIG_PCI
void uhci_reset_hc(struct pci_dev *pdev, unsigned long base);
int uhci_check_and_reset_hc(struct pci_dev *pdev, unsigned long base);
int usb_amd_find_chipset_info(void);
int usb_hcd_amd_remote_wakeup_quirk(struct pci_dev *pdev);
bool usb_amd_hang_symptom_quirk(void);
bool usb_amd_prefetch_quirk(void);
void usb_amd_dev_put(void);
void usb_amd_quirk_pll_disable(void);
void usb_amd_quirk_pll_enable(void);
void usb_enable_intel_xhci_ports(struct pci_dev *xhci_pdev);
void usb_disable_xhci_ports(struct pci_dev *xhci_pdev);
void sb800_prefetch(struct device *dev, int on);
#else
struct pci_dev;
static inline void usb_amd_quirk_pll_disable(void) {}
static inline void usb_amd_quirk_pll_enable(void) {}
static inline void usb_amd_dev_put(void) {}
static inline void usb_disable_xhci_ports(struct pci_dev *xhci_pdev) {}
static inline void sb800_prefetch(struct device *dev, int on) {}
#endif  /* CONFIG_PCI */

#endif  /*  __LINUX_USB_PCI_QUIRKS_H  */