The following evaluation was done in early May ....
In summary, EDR is brand new in upstream kernels and to my
knowledge has not been exercised in-house at Canonical, and may be
difficult to test due to a lack of systems with EDR functionality in
their firmware. I am unsure as to what the state of regression testing
is with regards to this type of PCI functionality.
Some followup patches and discussion after the original EDR
submission are below.
To be clear, these are not part of the request from Nvidia.
These are upstream followups to the EDR patch set, and are indicative of
the final state of this functionality still being in flux.
https://lore.kernel.org/linux-pci/[email protected]/
The above is unapplied upstream; it is proposed to fix an issue
with the negotiation between the operating system and firmware for
control for DPC, and as of 1 May 2020 is pending waiting for
https://lore.kernel.org/linux-pci/67af2931705bed9a588b5a39d369cb70b9942190.1587925636.git.sathyanarayanan.kuppusw...@linux.intel.com/
to be sorted out.
This patch (which is applied upstream to pci git tree for
merging in 5.8) relates to how the operating system and firmware
negotiate control of AER and DPC via the "firmware first" bit in the
ACPI HEST vs. using the _OSC ACPI method. Prior to this patch, the ACPI
HEST takes priority; after this patch, _OSC is the only method
consulted.
This second patch could:
(a) affect Nvidia's use of DPC / EDR, depending upon how their
firmware is negotiating the control with the operating system, and
(b) affect our existing installed base platforms that currently
end up negotiating one way, but end up with a different result under
this patch. E.g., the platform advertises "firmware first" in the ACPI
HEST, but not via _OSC. I think it is more likely that server class
systems will already do this correctly, and that embedded / "IoT" type
devices are more likely to see an impact from this change.
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https://bugs.launchpad.net/bugs/1885030
Title:
[Intel] Add Error Disconnect Recover support
Status in intel:
New
Status in linux package in Ubuntu:
Incomplete
Status in linux source package in Focal:
Incomplete
Status in linux source package in Groovy:
Incomplete
Bug description:
As per the following PCIe spec ECNs, implement EDR support in Linux
kernel and upstream it.
https://members.pcisig.com/wg/PCI-SIG/document/14076
https://members.pcisig.com/wg/PCI-SIG/document/12888
Patchset (Merged 5.7 mainline):
894020fdd88c PCI/AER: Rationalize error status register clearing
ac1c8e35a326 PCI/DPC: Add Error Disconnect Recover (EDR) support
aea47413e7ce PCI/DPC: Expose dpc_process_error(), dpc_reset_link() for use by
EDR
20e15e673b05 PCI/AER: Add pci_aer_raw_clear_status() to unconditionally clear
Error Status
27005618178e PCI/DPC: Cache DPC capabilities in pci_init_capabilities()
e8e5ff2aeec1 PCI/ERR: Return status of pcie_do_recovery()
b6cf1a42f916 PCI/ERR: Remove service dependency in pcie_do_recovery()
be06c1b42eea PCI/DPC: Move DPC data into struct pci_dev
6d2c89441571 PCI/ERR: Update error status after reset_link()
b5dfbeacf748 PCI/ERR: Combine pci_channel_io_frozen cases
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