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

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Message-ID: <ebc56ab0bd61f5b33be976a6643880db@codeaurora.org>
Date:   Fri, 05 Jun 2020 00:20:02 +0530
From:   Sibi Sankar <sibis@...eaurora.org>
To:     Evan Green <evgreen@...omium.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 2020-06-04 04:03, Evan Green wrote:
> 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

TL;DR
Sysmon when enabled adds a lookup
for qmi service 43 (Subsystem
control service). When we shutdown
the modem, we send a SSCTL_SHUTDOWN_REQ
to the service and the modem responds
with a shutdown-ack interrupt. If you
have rmtfs running with -v turned on
you can notice pending efs transactions
being completed followed by a bye I guess.

> 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>

Thanks for the review!

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