[PATCH v2] PCI/portdrv: Use link bandwidth notification capability bit

[Stuart Hayes <stuart.w.hayes@gmail.com>]

The pcieport driver can fail to attach to a downstream port that doesn't
support bandwidth notification.  This can happen when, in
pcie_port_device_register(), pci_init_service_irqs() tries (and fails) to
set up a bandwidth notification IRQ for a device that doesn't support it.

This patch changes get_port_device_capability() to look at the link
bandwidth notification capability bit in the link capabilities register of
the port, instead of assuming that all downstream ports have that
capability.

Signed-off-by: Stuart Hayes <stuart.w.hayes@gmail.com>
Reviewed-by: Lukas Wunner <lukas@wunner.de>
---

changes from v1:
	- corrected spelling errors in commit message
	- added Lukas' reviewed-by:

---
 drivers/pci/pcie/portdrv_core.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/pcie/portdrv_core.c b/drivers/pci/pcie/portdrv_core.c
index e1fed6649c41..3ee63968deaa 100644
--- a/drivers/pci/pcie/portdrv_core.c
+++ b/drivers/pci/pcie/portdrv_core.c
@@ -257,8 +257,13 @@ static int get_port_device_capability(struct pci_dev *dev)
 		services |= PCIE_PORT_SERVICE_DPC;
 
 	if (pci_pcie_type(dev) == PCI_EXP_TYPE_DOWNSTREAM ||
-	    pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT)
-		services |= PCIE_PORT_SERVICE_BWNOTIF;
+	    pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT) {
+		u32 linkcap;
+
+		pcie_capability_read_dword(dev, PCI_EXP_LNKCAP, &linkcap);
+		if (linkcap & PCI_EXP_LNKCAP_LBNC)
+			services |= PCIE_PORT_SERVICE_BWNOTIF;
+	}
 
 	return services;
 }
-- 
2.27.0