linux-kernel - Re: [PATCH] Revert "Revert "wifi: ath11k: Enable threaded NAPI""

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Date:   Thu, 10 Aug 2023 10:16:21 +0530
From:   Manikanta Pubbisetty <quic_mpubbise@...cinc.com>
To:     Johan Hovold <johan@...nel.org>
CC:     Johan Hovold <johan+linaro@...nel.org>,
        Kalle Valo <kvalo@...nel.org>,
        Jeff Johnson <quic_jjohnson@...cinc.com>,
        Bjorn Andersson <quic_bjorande@...cinc.com>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        <ath11k@...ts.infradead.org>, <linux-wireless@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Revert "Revert "wifi: ath11k: Enable threaded NAPI""



On 8/9/2023 2:46 PM, Johan Hovold wrote:
> On Wed, Aug 09, 2023 at 02:32:37PM +0530, Manikanta Pubbisetty wrote:
>> On 8/9/2023 1:04 PM, Johan Hovold wrote:
>>> This reverts commit d265ebe41c911314bd273c218a37088835959fa1.
>>>
>>> Disabling threaded NAPI causes the Lenovo ThinkPad X13s to hang (e.g. no
>>> more interrupts received) almost immediately during RX.
>>>
>>> Apparently something broke since commit 13aa2fb692d3 ("wifi: ath11k:
>>> Enable threaded NAPI") so that a simple revert is no longer possible.
>>>
>>
>> This is getting as weird as it would get :)
>>
>>> As commit d265ebe41c91 ("Revert "wifi: ath11k: Enable threaded NAPI"")
>>> does not address the underlying issue reported with QCN9074, it seems we
>>> need to reenable threaded NAPI before fixing both bugs properly.
>>>
>>
>> It seems that the revert has actually solved the issue reported with
>> QCN9074.
>>
>> https://bugzilla.kernel.org/show_bug.cgi?id=217536
> 
> Sure, but it's only a workaround as the underlying cause has not been
> identified.
> 
>> We were trying to reproduce the problem on X86+QCN9074 (with threaded
>> NAPI) from quite some time, but there is no repro yet.
>>
>> Actually, enabling/disabling threaded NAPI is a simple affair; I'm
>> wondering to hear that interrupts are blocked due  to not having
>> threaded NAPI.
> 
> It sounds to me like the driver's locking is broken if moving to softirq
> processing hangs the machine like this. But I have not had time to try
> to try to track it down besides verifying that reenabling threaded NAPI
> makes the problem go away.
> 
>> What is the chip that Lenovo Thinkpad X13s is having?
> 
> It's a WCN6855 (QCNFA765).
> 

Also it is worth to give a try with this patch here 
https://patchwork.kernel.org/project/linux-wireless/patch/20230601033840.2997-1-quic_bqiang@quicinc.com/ 
. This seems to be fixing some known interrupt issue on WCN6855. Could 
you pls give a try?

Thanks,
Manikanta