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

[Wim ten Have]

On Fri, 7 Jul 2017 11:01:16 -0400
Sinan Kaya <okaya at codeaurora.org> wrote:

> Hi Wim,
> 
> On 7/7/2017 10:53 AM, Sinan Kaya wrote:
> > According to extended tags ECN document, all PCIe receivers are expected
> > to support extended tags support. It should be safe to enable extended
> > tags on endpoints without checking compatibility.
> > 
> > This assumption seems to be working fine except for the legacy systems.
> > The ECN has been written against PCIE spec version 2.0. Therefore, we need
> > to exclude all version 1.0 devices from this change as there is HW out
> > there that can't handle extended tags.
> > 
> > Note that the default value of Extended Tags Enable bit is implementation
> > specific. Therefore, we are clearing the bit by default when incompatible
> > HW is found without assuming that value is zero.
> > 
> > Reported-by: Wim ten Have <wim.ten.have at oracle.com>
> > Link: https://pcisig.com/sites/default/files/specification_documents/ECN_Extended_Tag_Enable_Default_05Sept2008_final.pdf
> > Link: https://bugzilla.redhat.com/show_bug.cgi?id=1467674
> > Fixes: 60db3a4d8cc9 ("PCI: Enable PCIe Extended Tags if supported")
> > Signed-off-by: Sinan Kaya <okaya at codeaurora.org>
> > ---  
> 
> Can you also give this a spin? I don't have a system with v1 PCIe bridges.
> I only tested v2 and later code path.
> 
> I tried to address Jike Song concerns on this version and removed your tested-by
> since the code changed.
> 
> Sinan
> 

Sure,

-- 
Wim ten Have | Consulting Member of Technical Staff
Oracle Linux and VM Development Engineering
ORACLE Nederland BV | Hertogswetering 163-167 | 3543 AS Utrecht/NL