On Tue, Jan 30, 2018 at 09:41:21AM +0100, Stefan Roese wrote: > Hotplugging of some PCIe devices on our platform sometimes leads to a > bounce of link-up and link-down events, resulting in problems in the > corresponding PCI drivers. > > Here an example of such a hotplug event bounce for a AHCI PCIe card: > ... > pciehp 0000:00:1c.1:pcie004: Slot(1): Card present > pciehp 0000:00:1c.1:pcie004: Slot(1): Link Up > pciehp 0000:00:1c.1:pcie004: Slot(1): Link Up event ignored; already powering on > pciehp 0000:00:1c.1:pcie004: Slot(1): Link Down > pciehp 0000:00:1c.1:pcie004: Slot(1): Card present > pciehp 0000:00:1c.1:pcie004: Slot(1): Link Up It would be good to find out why this happens in the first place. Perhaps there is some environmental interference or something causing this? > pci 0000:02:00.0: [1b4b:9215] type 00 class 0x010601 > pci 0000:02:00.0: reg 0x10: [io 0x8000-0x8007] > ... > ata3: SATA max UDMA/133 abar m2048@0x80910000 port 0x80910100 irq 100 > ata4: SATA max UDMA/133 abar m2048@0x80910000 port 0x80910180 irq 100 > ata5: SATA max UDMA/133 abar m2048@0x80910000 port 0x80910200 irq 100 > ata6: SATA max UDMA/133 abar m2048@0x80910000 port 0x80910280 irq 100 > pciehp 0000:00:1c.1:pcie004: Slot(1): Link Up event ignored; already powering on > ahci 0000:02:00.0: PME# disabled > ata3: SATA link down (SStatus 0 SControl 300) > ata5: SATA link down (SStatus 0 SControl 300) > ata4: SATA link down (SStatus 0 SControl 300) > WARNING: CPU: 2 PID: 1162 at drivers/ata/libata-core.c:6620 ata_host_detach+0x125/0x130 I think the AHCI driver should be fixed to cope with this. > ata6: SATA link down (SStatus 0 SControl 300) > Modules linked in: > CPU: 2 PID: 1162 Comm: kworker/u8:5 Not tainted 4.15.0+ #26 > Hardware name: congatec conga-qeval20-qa3-e3845/conga-qeval20-qa3-e3845, BIOS 2018.01-00033-g0125f37185-dirty 01/18/2018 > Workqueue: pciehp-1 pciehp_power_thread > ... > > This patch now adds the 'pciehp_debounce_time' module parameter, which > can be used to drop all events for the specified time (in milliseconds) > after a link-up event occurred. A value of ~100ms works fine in my tests > to debounce all the link-up / link-down events in my tests. This sounds a bit "hackish". I would rather make sure we can handle situations like this properly without passing additional parameters.
