linux-kernel - AMD Ryzen: pci 0000:00:00.2: can't derive routing for PCI INT A

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Date:   Thu, 28 May 2020 17:45:10 +0200
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     Bjorn Helgaas <bhelgaas@...gle.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>
Cc:     linux-pci@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Thomas Lendacky <Thomas.Lendacky@....com>,
        Mario Limonciello <mario.limonciello@...l.com>
Subject: AMD Ryzen: pci 0000:00:00.2: can't derive routing for PCI INT A

Dear Linux folks,


On most (if not all) AMD Ryzen systems, including the Dell OptiPlex 
5055, [1][2], Linux prints the warning below:

     $ dmesg --level=warn
     [    0.871377] pci 0000:00:00.2: can't derive routing for PCI INT A
     [    0.871732] pci 0000:00:00.2: PCI INT A: not connected
     [    0.884890]  PPR NX GT IA GA PC GA_vAPIC
     $ more /proc/version
     Linux version 5.4.39.mx64.334 (root@....molgen.mpg.de) (gcc version 
7.5.0 (GCC)) #1 SMP Thu May 7 14:27:50 CEST 2020
     pmenzel@...ut:~$ dmesg | grep 'DMI:'
     [    0.000000] DMI: Dell Inc. OptiPlex 5055 Ryzen CPU/0P03DX, BIOS 
1.1.20 05/31/2019

The system seems to work fine. What effect might be caused by the 
missing routing information?

I assume this is a firmware issue? Can I patch the ACPI tables to 
provide the correct information?

Should this indeed be an AMD AGESA issue, it be great, if somebody with 
contacts at AMD could be forward this to the appropriate folks.


Kind regards,

Paul


[1]: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1804589
[2]: https://bugs.launchpad.net/dell-sputnik/+bug/1881121