On 6/19/2018 5:43 PM, Bjorn Helgaas wrote: >> Hotplug driver removes the device from system when a link down interrupt >> is observed and performs re-enumeration when link up interrupt is observed. >> >> This conflicts with what this code is trying to do. Try secondary bus reset >> only if pci_reset_slot() fails/unsupported. > Hi Sinan, > > We had a bunch of discussion here but not sure we ever reached a > consensus. It did seem like we'd like to avoid putting hotplug > knowledge in drivers, though. What do you think the path forward is? > There are multiple issues. We discussed the need for a retrain API on this thread. However, retrain API may not be enough for this particular usage as the device might need a full link training sequence following firmware load including a hot reset message. I don't think we can remove the bus reset usage in this code. I'd like to start with a small one to address your comment here. "I think my concern is that knowledge about this reset/link down/hotplug issue is leaking out and we'll end up with different reset interfaces that may or may not result in hotplug events. This seems like a confusing API because it's hard to explain which interface a driver should use." I'm thinking of removing pci_reset_slot() and pci_try_reset_slot() functions as an exported API and fold them into pci_reset_bus() and pci_try_reset_bus() API respectively. This is what happens when you insert a fatal error to a hotplug slot. See multiple link up/down messages. /_#_[__333.699731]_pcieport_0001:00:00.0:_AER:_Uncorrected_(Fatal)_error_received:_id=0000 [ 333.748116] pcieport 0001:00:00.0: PCIe Bus Error: severity=Uncorrected (Fatal), type=Transaction Layer, id [ 333.816044] pcieport 0001:00:00.0: device [17cb:0404] error status/mask=00040000/00400000 [ 333.871581] pcieport 0001:00:00.0: [18] Malformed TLP (First) [ 333.914675] pcieport 0001:00:00.0: TLP Header: 40000001 000000ff 00000000 00000000 [ 333.968397] pciehp 0001:00:00.0:pcie004: Slot(2): Link Down [ 334.043234] iommu: Removing device 0001:01:00.4 from group 0 [ 334.095952] iommu: Removing device 0001:01:00.3 from group 0 [ 334.144644] iommu: Removing device 0001:01:00.2 from group 0 [ 334.194653] iommu: Removing device 0001:01:00.1 from group 0 [ 334.243564] pciehp 0001:00:00.0:pcie004: Slot(2): Link Up [ 334.282556] iommu: Removing device 0001:01:00.0 from group 0 [ 334.330994] pciehp 0001:00:00.0:pcie004: Slot(2): Link Up event queued; currently getting powered off [ 334.890587] pciehp 0001:00:00.0:pcie004: Timeout on hotplug command 0x13f1 (issued 282900 msec ago) [ 335.070190] pciehp 0001:00:00.0:pcie004: Slot(2): Link Down [ 335.106960] pciehp 0001:00:00.0:pcie004: Slot(2): Link Down event queued; currently getting powered on [ 335.191119] pcieport 0001:00:00.0: AER: Device recovery failed [ 346.590153] pciehp 0001:00:00.0:pcie004: Timeout on hotplug command 0x17f1 (issued 10250 msec ago) As a suggestion: 1. If the device belongs to a slot, do slot reset. 2. Otherwise, do bus reset. Since Oza's DPC/AER patch to refactor fatal error handling, both hotplug driver and AER/DPC driver will try removing devices and perform enumeration on link events/AER events. Perfect environment for race condition without a change. -- Sinan Kaya Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.
