Messages in this thread | | | Subject | Re: [PATCH v17 09/12] PCI/AER: Allow clearing Error Status Register in FF mode | From | Kuppuswamy Sathyanarayanan <> | Date | Thu, 12 Mar 2020 15:02:07 -0700 |
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Hi,
On 3/12/20 2:52 PM, Bjorn Helgaas wrote: > On Thu, Mar 12, 2020 at 02:29:58PM -0700, Kuppuswamy Sathyanarayanan wrote: >> Hi, >> >> On 3/12/20 2:02 PM, Austin.Bolen@dell.com wrote: >>> On 3/12/2020 2:53 PM, Bjorn Helgaas wrote: >>>> On Wed, Mar 11, 2020 at 04:07:59PM -0700, Kuppuswamy Sathyanarayanan wrote: >>>>> On 3/11/20 3:23 PM, Bjorn Helgaas wrote: >>>>>> Is any synchronization needed here between the EDR path and the >>>>>> hotplug/enumeration path? >>>>> If we want to follow the implementation note step by step (in >>>>> sequence) then we need some synchronization between EDR path and >>>>> enumeration path. But if it's OK to achieve the same end result by >>>>> following steps out of sequence then we don't need to create any >>>>> dependency between EDR and enumeration paths. Currently we follow >>>>> the latter approach. >>>> What would the synchronization look like? >>>> >>>> Ideally I think it would be better to follow the order in the >>>> flowchart if it's not too onerous. That will make the code easier to >>>> understand. The current situation with this dependency on pciehp and >>>> what it will do leaves a lot of things implicit. >>>> >>>> What happens if CONFIG_PCIE_EDR=y but CONFIG_HOTPLUG_PCI_PCIE=n? >>>> >>>> IIUC, when DPC triggers, pciehp is what fields the DLLSC interrupt and >>>> unbinds the drivers and removes the devices. If that doesn't happen, >>>> and Linux clears the DPC trigger to bring the link back up, will those >>>> drivers try to operate uninitialized devices? >>>> >>>> Does EDR need a dependency on CONFIG_HOTPLUG_PCI_PCIE? >>> From one of Sathya's other responses: >>> >>> "If hotplug is not supported then there is support to enumerate >>> devices via polling or ACPI events. But a point to note >>> here is, enumeration path is independent of error handler path, and >>> hence there is no explicit trigger or event from error handler path >>> to enumeration path to kick start the enumeration." >>> >>> The EDR standard doesn't have any dependency on hot-plug. It sounds like >>> in the current implementation there's some manual intervention needed if >>> hot-plug is not supported? >> No, there is no need for manual intervention even in non hotplug >> cases. >> >> For ACPI events case, we would rely on ACPI event to kick start the >> enumeration. And for polling model, there is an independent polling >> thread which will kick start the enumeration. > I'm guessing the ACPI case works via hotplug_is_native(): if > CONFIG_HOTPLUG_PCI_PCIE=n, pciehp_is_native() returns false, and > acpiphp manages hotplug. > > What if CONFIG_HOTPLUG_PCI_ACPI=n also? If none of the auto scans are enabled then we might need some manual trigger ( rescan). But this would be needed in native DPC case as well. > > Where is the polling thread? drivers/pci/hotplug/pciehp_hpc.c > >> Above both enumeration models are totally independent and has >> no dependency on error handler thread. > I see they're currently independent from the EDR thread, but it's not > clear to me that there's no dependency. After all, both EDR and the > hotplug paths are operating on the same devices at roughly the same > time, so we should have some story about what keeps them from getting > in each other's way. > >> We will decide which model to use based on hardware capability and >> _OSC negotiation or kernel command line option.
-- Sathyanarayanan Kuppuswamy Linux kernel developer
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