On Thu, Nov 29, 2018 at 06:57:37PM +0000, Alex_Gagniuc@xxxxxxxxxxxx wrote: > On 11/29/2018 11:36 AM, Bjorn Helgaas wrote: > > On Wed, Nov 28, 2018 at 06:08:24PM -0600, Alexandru Gagniuc wrote: > >> A warning is generated when a PCIe device is probed with a degraded > >> link, but there was no similar mechanism to warn when the link becomes > >> degraded after probing. The Link Bandwidth Notification provides this > >> mechanism. > >> > >> Use the link bandwidth notification interrupt to detect bandwidth > >> changes, and rescan the bandwidth, looking for the weakest point. This > >> is the same logic used in probe(). > > > > I like the concept of this. What I don't like is the fact that it's > > tied to pciehp, since I don't think the concept of Link Bandwidth > > Notification is related to hotplug. So I think we'll only notice this > > for ports that support hotplug. Maybe it's worth doing it this way > > anyway, even if it could be generalized in the future? > > That makes sense. At first, I thought that BW notification was tied to > hotplug, but our PCIe spec writer disagreed with that assertion. I'm > just not sure where to handle the interrupt otherwise. I guess the interrupt is shared with hotplug and PME? In that case write a separate pcie_port_service_driver and request the interrupt with IRQF_SHARED. Define a new service type in drivers/pci/pcie/portdrv.h. Amend get_port_device_capability() to check for PCI_EXP_LNKCAP_LBNC. Thanks, Lukas
