Re: [PATCH v2 0/4] firmware: arm_scmi: Enable building SCMI as module

From: Sudeep Holla <sudeep.holla@arm.com>
To: Cristian Marussi <cristian.marussi@arm.com>
Cc: Mikhail Golubev <mikhail.golubev@opensynergy.com>,
	Peter Hilber <peter.hilber@opensynergy.com>,
	Igor Skalkin <Igor.Skalkin@opensynergy.com>,
	linux-arm-kernel@lists.infradead.org,
	Anton Yakovlev <Anton.Yakovlev@opensynergy.com>
Subject: Re: [PATCH v2 0/4] firmware: arm_scmi: Enable building SCMI as module
Date: Tue, 8 Sep 2020 12:11:14 +0100	[thread overview]
Message-ID: <20200908111105.GA16927@bogus> (raw)
In-Reply-To: <20200908090844.GA30729@e119603-lin.cambridge.arm.com>

On Tue, Sep 08, 2020 at 10:08:44AM +0100, Cristian Marussi wrote:
> Hi Sudeep
>
> On Mon, Sep 07, 2020 at 08:50:42PM +0100, Sudeep Holla wrote:
> > Hi,
> >
> > Though it was initially developed as module, so some reason(I can't
> > recollect why apart from some structuring arounf the way bus and
> > protocols were initialised), it was merged as a built-in only driver.
> >
> > Now, there is a need to build this as modules. This is mainly needed
> > by virtio transport. This also aligns well with GKI modularisation
> > efforts.
> >
> > Regards,
> > Sudeep
> >
>
> I re-tested this v2 (also regarding some interactions with notifications) and
> works generally fine for me, both builtin or modularized, BUT I've seen an
> issue on core module load/unload/load.
> Basically doing this:
>
> (debian-arm64)root@debarm64:~# insmod ./scmi-module.ko
> (debian-arm64)root@debarm64:~# insmod ./scmi-cpufreq.ko
>
> (debian-arm64)root@debarm64:~# rmmod ./scmi-cpufreq.ko
> (debian-arm64)root@debarm64:~# rmmod ./scmi-module.ko
> (debian-arm64)root@debarm64:~# lsmod
> Module                  Size  Used by
> (debian-arm64)root@debarm64:~# insmod ./scmi-module.ko
>
> I've got this:
>
>
> [  146.982413] mhu 2b1f0000.mhu: Channel in use
> [  146.982433] arm-scmi firmware:scmi: failed to request SCMI Tx mailbox
> [  146.982472] arm-scmi: probe of firmware:scmi failed with error -16
>
> and SCMI is broken then after reloading.
>
> Now this is an issue I've seen already in my ongoing WIP on full SCMI Protocols
> modularization for custom protocols, and it is related to the fact the the
> underlying transport init is bound to the SCMI device creation and not the
> protocol initialization, and we are not destroying and re-creating such
> devices properly. (things that I'm going to address in that WIP)
>
> Given that the solution to this is not so simple as of now, and given that
> unloading of the core as a whole module does not make so much sense anyway
> (while it will be needed for single custom protocols modules), couldn't we
> just make scmi-module a permanent by droppping module_exit() ?

Now I remember why I had bus_exit before unregistering the driver. I think
that should fix the issue. Let me know.

--
Regards,
Sudeep

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel