Buss Reset Problem

Michal Kazior michal.kazior at tieto.com
Thu Jul 9 22:48:26 PDT 2015

On 9 July 2015 at 16:11,  <CACook at quantum-sci.com> wrote:
> On Thursday 09 July 2015 15:46:55 Michal Kazior wrote:
>> > So that's it for the Doodle Labs ACE-DB-3.  It went back yesterday -- doesn't work with Linux.
>> I think someone complained they couldn't get an XB design to work on
>> some of their PCI-E hosts (some Atom laptop even refused to POST with
>> the card if I recall correctly). Apparently there's an electrical
>> quirk - or at least that was to conclusion back then.
>> > It's not the buss reset problem as I patched quirks.c.
>> I wonder how much related this could be to Data Bus Error ath10k sees
>> when doing cold resets sometimes. Maybe it's good to have the quirk
>> fixup nonetheless? But I'm no PCI expert so what do I know.
> Yes the problem is very early in boot.  In KVM guest almost right after Grub it says that PCIe address does not exist (or is not accessible), and sure enough I check it on the host and it's flipped to "Invalid header".  I have to reboot the _host_ to get the card back then.

I wonder how much this is fault of the card and the IOMMU and/or vfio itself.

I've been using pci-stub and qemu's pci-assign to virtualize ath10k
for quite some time now. It does herp-derp on me occasionally but
never* did it require me to reboot the host.

I briefly tried to use vfio but it wasn't working well for me (can't
remember the details).

* The cold reset problem can hard lock-up the host sometimes. If you
load ath10k_pci with reset_mode=1 both on host and guest then it
doesn't require reboots of any sorts.

> The card has good specs but Doodle doesn't care about this problem, and I just don't have time to uselessly fiddle with it.

Sorry to hear that.


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