Re: [PATCH V2] PCI: Do not enable extended tags on pre-dated (v1.x) systems

[Sinan Kaya]

Hi Bjorn,

On 7/10/2017 7:09 PM, Bjorn Helgaas wrote:
> The PCI_EXP_DEVCTL_EXT_TAG bit controls the behavior of the function as a
> Requester.  As far as I can see, it has nothing to do with whether the
> function supports 8-bit tags as a *Completer*, so the implicit assumption
> of the spec is that all Completers always support 8-bit tags.  My guess is
> that's why the ECN thought it would be safe to enable extended tags by
> default.
> 
> If that's the case, this is just a defect in the device (the Completer),
> and we should blacklist it.  Looking at the PCIe Capability version might
> happen to correlate with Completer support for 8-bit tags, but that looks
> like just a coincidence to me.

Sure, I can change to blacklist. I'll not enable it unless the device is blacklisted
via quirks.

Sinan
-- 
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.