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

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Date:   Wed, 11 Apr 2018 10:02:07 -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,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] PCI: quirk HT1100 & HT2000 and one HT2100 Root Ports for
 Extended Tags

+GregKH

On 4/11/2018 9:51 AM, Bjorn Helgaas wrote:
> On Tue, Apr 10, 2018 at 04:18:01PM -0400, Sinan Kaya wrote:
>> 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. 
> 
> We started enabling extended tags with 60db3a4d8cc9 ("PCI: Enable PCIe
> Extended Tags if supported"), which appeared in v4.11.
> 
> So I added these stable tags:
> 
>   CC: stable@...r.kernel.org      # v4.11: 62ce94a7a5a5 PCI: Mark Broadcom HT2100 Root Port Extended Tags as broken
>   CC: stable@...r.kernel.org      # v4.11
> 
> I'm not sure I'm using the stable request correctly, but my intent is:
> 
>   - 62ce94a7a5a5 appeared in v4.14, so cherry-pick 62ce94a7a5a5 to
>     v4.11 through v4.13
>   - cherry-pick *this* patch on top of 62ce94a7a5a5 to v4.11 and later
> 


-- 
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.