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

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Date:   Wed, 9 Aug 2023 11:16:06 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Manikanta Pubbisetty <quic_mpubbise@...cinc.com>
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 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).

Johan