linux-kernel - Re: [PATCH] PCI: quirk HT1100 & HT2000 and one HT2100 Root Ports for Extended Tags

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Date:   Tue, 10 Apr 2018 16:18:01 -0400
From:   Sinan Kaya <okaya@...eaurora.org>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     linux-pci@...r.kernel.org, sulrich@...eaurora.org,
        timur@...eaurora.org, linux-arm-msm@...r.kernel.org,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        open list <linux-kernel@...r.kernel.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] PCI: quirk HT1100 & HT2000 and one HT2100 Root Ports for
 Extended Tags

On 4/10/2018 3:50 PM, Bjorn Helgaas wrote:
> On Tue, Apr 10, 2018 at 02:41:44PM -0500, Bjorn Helgaas wrote:
>> On Wed, Apr 04, 2018 at 06:50:09PM -0400, Sinan Kaya wrote:
>>> Per PCIe r3.1, sec 2.2.6.2 and 7.8.4, a Requester may not use 8-bit Tags
>>> unless its Extended Tag Field Enable is set, but all Receivers/Completers
>>> must handle 8-bit Tags correctly regardless of their Extended Tag Field
>>> Enable.
>>>
>>> Some devices do not handle 8-bit Tags as Completers, so add a quirk for
>>> them.  If we find such a device, we disable Extended Tags for the entire
>>> hierarchy to make peer-to-peer DMA possible.
>>>
>>> The Broadcom HT1100/HT2000/HT2100 seems to have issues with handling 8-bit
>>> tags.  Mark it as broken.
>>>
>>> Fixes: 60db3a4d8cc9 ("PCI: Enable PCIe Extended Tags if supported")
>>> Link: https://bugzilla.kernel.org/show_bug.cgi?id=196197
>>> Signed-off-by: Sinan Kaya <okaya@...eaurora.org>
>> Applied to pci/enumeration for v4.18, thanks!
> Actually, this is a really annoying issue and I think the fix is
> appropriate for v4.17, so I moved it to my for-linus branch.
> 

I agree. It causes boot issues on some AMD Opteron machines. It should
probably be back-ported too. 

-- 
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.