Re: [PATCH] PCI: Disable NoSnoop and Relaxed ordering for Intel wireless BE200

On 29/07/26 12:19 pm, Grumbach, Emmanuel wrote:
> On Tue, 2026-07-28 at 15:18 -0500, Bjorn Helgaas wrote:
>> On Tue, Jul 28, 2026 at 07:47:04PM +0000, Grumbach, Emmanuel wrote:
>>> On Tue, 2026-07-28 at 14:24 -0500, Bjorn Helgaas wrote:
>>>> On Tue, Jul 28, 2026 at 06:21:23PM +0000, Grumbach, Emmanuel
>>>> wrote:
>>>>> On Tue, 2026-07-28 at 13:03 -0500, Bjorn Helgaas wrote:
>>>>> ...
>>>>
>>>>>> AFAICS we still don't know why Tegra264 would set NoSnoop
>>>>>> and/or RlxdOrd in the MMIO read.
>>>>>
>>>>> Me neither but... I can't comment on that. And de-facto, once
>>>>> it
>>>>> does that, the BE200 replies with the NoSnoop and RlxOrd clear
>>>>> in the TLP which is then considered as a malformed TLP.
>>>>>
>>>>>> Unless iwlwifi asked for NoSnoop and/or RlxdOrd to be set, I
>>>>>> think it's a potential problem for drivers if Tegra264 sets
>>>>>> them.
>>>>>
>>>>> I ... don't think we would do that. The driver would certainly
>>>>> not do that... Regarding the hardware itself, I can't comment,
>>>>> but I can check internally.
>>>>
>>>> Forgot to ask, can you collect the output of "sudo lspci -vv", at
>>>> least for the RP and the BE200?
>>>>
>>>> And maybe the dmesg log when booted with "log_buf_len=16M
>>>> pci=earlydump" as well, so we can see if attributes were enabled
>>>> by a
>>>> bootloader?
>>>
>>> I assume you want all this without the quirk, right?
>>
>> Right.
> 
> Attached.
> Note that we used an out-of-tree driver in those attempts so the kernel
> is tainted, but this does not impact the issue we're discussing here.
> 

PCI_EXP_DEVCTL_RELAX_EN and PCI_EXP_DEVCTL_NOSNOOP_EN are set by HW 
default value, this is inline with PCIe spec. It says "the default value 
of this bit is 1b" in both cases.

Thanks,
Manikanta

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nvpublic