[regression] mhi: ath11k resume fails on some devices

[Loic Poulain]

Hi Kalle,

On Fri, 24 Sept 2021 at 10:36, Kalle Valo <kvalo at codeaurora.org> wrote:
>
> Loic Poulain <loic.poulain at linaro.org> writes:
>
> > Hi Kalle,
> >
> > On Thu, 16 Sept 2021 at 10:00, Kalle Valo <kvalo at codeaurora.org> wrote:
> >>
> >> Hi Loic and Mani,
> >>
> >> I hate to be the bearer of bad news again :)
> >>
> >> I noticed already a while ago that commit 020d3b26c07a ("bus: mhi: Early
> >> MHI resume failure in non M3 state"), introduced in v5.13-rc1, broke
> >> ath11k resume on my NUC x86 testbox using QCA6390. Interestingly enough
> >> Dell XPS 13 9310 laptop (with QCA6390 as well) does not have this
> >> problem, I only see the problem on the NUC. I do not know what's causing
> >> this difference.
> >
> > I suppose the NUC is current PCI-Express power during suspend while
> > the laptop maintains PCIe/M2 power.
>
> Sorry, I'm not able to parse that sentence. Can you elaborate more?

Ouch, yes, I wanted to say that the NUC does not maintain the power of
PCI express during suspend (leading to PCI D3cold state), whereas the
laptop maintains the power of the M2 card... well, not sure now I see
your logs.

>
> >> At the moment I'm running my tests with commit 020d3b26c07a reverted and
> >> everything works without problems. Is there a simple way to fix this? Or
> >> maybe we should just revert the commit? Commit log and kernel logs from
> >> a failing case below.
> >
> > Do you have log of success case?
>
> A log from a successful case in the end of email, using v5.15-rc1 plus
> revert of commit 020d3b26c07abe27.
>
> > To me, the device loses power, that is why MHI resuming is failing.
> > Normally the device should be properly recovered/reinitialized. Before
> > that patch the power loss was simply not detected (or handled at
> > higher stack level).
>
> Currently in ath11k we always keep the firmware running when in suspend,
> this is a workaround due to problems between mac80211 and MHI stack.
> IIRC the problem was something related MHI creating struct device during
> resume or something like that.

Could you give a try with the attached patch? It should solve your
issue without breaking modem support.

Regards,
Loic
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