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

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Date:   Wed, 03 Jun 2020 10:59:42 +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

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.

> 
> I just worry this will mask real issues that happen during graceful 
> shutdown.
> -Evan

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