linux-kernel - Re: [PATCH] remoteproc: qcom_q6v5: don't auto boot remote processor

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Date:   Fri, 18 Jan 2019 10:35:50 -0800
From:   Brian Norris <briannorris@...omium.org>
To:     Sibi Sankar <sibis@...eaurora.org>
Cc:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Ramon Fried <ramon.fried@...il.com>,
        linux-remoteproc@...r.kernel.org,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        linux-kernel-owner@...r.kernel.org
Subject: Re: [PATCH] remoteproc: qcom_q6v5: don't auto boot remote processor

On Thu, Jan 17, 2019 at 11:04 PM Sibi Sankar <sibis@...eaurora.org> wrote:
> On 2018-05-29 09:50, Bjorn Andersson wrote:
> > On Thu 24 May 12:21 PDT 2018, Ramon Fried wrote:

Whoa, bringing up a 7-month old patch? Nice.

> >> Sometimes that rmtfs userspace module is not brought
> >> up fast enough and the modem crashes.
> >> disabling automated boot in the driver and triggering
> >> the boot from user-space sovles the problem.
> >>
> >> Signed-off-by: Ramon Fried <ramon.fried@...il.com>
> >
> > Thanks for your patch Ramon. While this nudges the behavior to make
> > things work slightly better I think we need to describe the explicit
> > dependency between the mss firmware and the existence of rmtfs.
> >
> > As our remoteprocs are essentially always-on I would prefer that they
> > start "automatically" and not through use of the sysfs interface.
> >
> > But we're at the point where this is a real problem on 410, 820 and
> > 845,
> > so we have to come up with some way to tie these pieces together. If
> > your patch suits that solution I will happily take it.
> >
> > Regards,
> > Bjorn
>
> After experimenting with in kernel solutions for
> three revisions and observing problems on graceful
> shutdown usecase,

What exactly were the problems again? e.g., what were the deficiencies
with having the remoteproc device listen for the REMOTEFS_QMI_SVC_ID
service again? Sorry, but I sort of dropped off on reviewing that
stuff, and now I see this. I'd mildly prefer something that is
actually automatic, but if I'm missing some aspects, I'd like to hear
that. (And, I'd like to see them explained in the commit message, if
this is ever to be merged.)

> switching to controlling the
> remoteproc mss through rmtfs seems to solve all
> the known issues.

How so? It explicitly does NOT help at all if RMTFS crashes.
Because...who's going to stop the modem in that case? (It works if you
automatically respawn a new RMTFS daemon, to toggle the modem. But
that's kind of cheating, and you can do that anyway, even without this
patch.) On the contrary, your patch *would* resolve that, since the
modem would notice when the RMTFS server goes away, and it would stop
itself.

> https://patchwork.kernel.org/patch/10662395/
>
> we should probably get this merged in, now that
> we are planning to start/stop mss through
> rmtfs.

Sorry, who's planning to stop mss through rmtfs? Did I miss something?

Brian