linux-kernel - Re: [PATCH 1/2] remoteproc: qcom: q6v5: Update running state before requesting stop

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Message-ID: <CAE=gft4v1iHAPJS13fLBXgjt8ZRhD7q894zF_7JvK9QbiTbwhA@mail.gmail.com>
Date:   Wed, 3 Jun 2020 15:33:55 -0700
From:   Evan Green <evgreen@...omium.org>
To:     Sibi Sankar <sibis@...eaurora.org>
Cc:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Andy Gross <agross@...nel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        linux-remoteproc@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Ohad Ben Cohen <ohad@...ery.com>, rohitkr@...eaurora.org,
        stable@...r.kernel.org, linux-kernel-owner@...r.kernel.org
Subject: Re: [PATCH 1/2] remoteproc: qcom: q6v5: Update running state before
 requesting stop

On Tue, Jun 2, 2020 at 10:29 PM Sibi Sankar <sibis@...eaurora.org> wrote:
>
> Evan,
> Thanks for taking time to review
> the series.
>
> On 2020-06-02 23:14, Evan Green wrote:
> > On Tue, Jun 2, 2020 at 9:33 AM Sibi Sankar <sibis@...eaurora.org>
> > wrote:
> >>
> >> Sometimes the stop triggers a watchdog rather than a stop-ack. Update
> >> the running state to false on requesting stop to skip the watchdog
> >> instead.
> >>
> >> Error Logs:
> >> $ echo stop > /sys/class/remoteproc/remoteproc0/state
> >> ipa 1e40000.ipa: received modem stopping event
> >> remoteproc-modem: watchdog received: sys_m_smsm_mpss.c:291:APPS force
> >> stop
> >> qcom-q6v5-mss 4080000.remoteproc-modem: port failed halt
> >> ipa 1e40000.ipa: received modem offline event
> >> remoteproc0: stopped remote processor 4080000.remoteproc-modem
> >>
> >> Fixes: 3b415c8fb263 ("remoteproc: q6v5: Extract common resource
> >> handling")
> >> Cc: stable@...r.kernel.org
> >> Signed-off-by: Sibi Sankar <sibis@...eaurora.org>
> >> ---
> >
> > Are you sure you want to tolerate this behavior from MSS? This is a
> > graceful shutdown, modem shouldn't have a problem completing the
> > proper handshake. If they do, isn't that a bug on the modem side?
>
> The graceful shutdown is achieved
> though sysmon (enabled using
> CONFIG_QCOM_SYSMON). When sysmon is
> enabled we get a shutdown-ack when we
> try to stop the modem, post which
> request stop is a basically a nop.
> Request stop is done to force stop
> the modem during failure cases (like
> rmtfs is not running and so on) and
> we do want to mask the wdog that we get
> during this scenario ( The locking
> already prevents the servicing of the
> wdog during shutdown, the check just
> prevents the scheduling of crash handler
> and err messages associated with it).
> Also this check was always present and
> was missed during common q6v5 resource
> helper migration, hence the unused
> running state in mss driver.

So you're saying that the intention of the ->running check already in
q6v5_wdog_interrupt() was to allow either the stop-ack or wdog
interrupt to complete the stop. This patch just fixes a regression
introduced during the refactor.
This patch seems ok to me then. It still sort of seems like a bug that
the modem responds arbitrarily in one of two ways, even to a "harsh"
shutdown request.

I wasn't aware of QCOM_SYSMON. Reading it now, It seems like kind of a
lot... do I really need all this? Can I get by with just remoteproc
stops?
Anyway, for this patch:

Reviewed-by: Evan Green <evgreen@...omium.org>