Re: [PATCH 1/5] firmware: arm_scmi: always initialize protocols

From: Sudeep Holla <sudeep.holla@arm.com>
To: Etienne Carriere <etienne.carriere@linaro.org>
Cc: Souvik Chakravarty <Souvik.Chakravarty@arm.com>,
	linux-kernel@vger.kernel.org,
	"moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE"
	<linux-arm-kernel@lists.infradead.org>,
	Sudeep Holla <sudeep.holla@arm.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Cristian Marussi <cristian.marussi@arm.com>
Subject: Re: [PATCH 1/5] firmware: arm_scmi: always initialize protocols
Date: Mon, 12 Oct 2020 10:32:12 +0100	[thread overview]
Message-ID: <20201012092827.GB16519@bogus> (raw)
In-Reply-To: <CAN5uoS9YffDZa6YOnJ_35ueMbkvCPuQ1=0KAuX5=k=kQYm+_Ng@mail.gmail.com>

On Fri, Oct 09, 2020 at 02:31:55PM +0200, Etienne Carriere wrote:
> On Thu, 8 Oct 2020 at 21:17, Sudeep Holla <sudeep.holla@arm.com> wrote:
> >
> > On Thu, Oct 08, 2020 at 04:37:18PM +0200, Etienne Carriere wrote:
> > > Remove the IDR replacement that prevent initializing an SCMI protocol
> > > when it has already been initialized. This is needed when there are
> > > several SCMI agents that do implement a given SCMI protocol unless
> > > what only the related SCMI protocol communication is initialized only
> > > for first probed agent.
> > >
> >
> > Can you please elaborate on your usecase please. What do you mean by several
> > SCMI agents here. OSPM is the only agent we are interested here. What
> > other agents is this driver supposed to handle here. We allocate memory
> > in init and calling init multiple times messes up the allocated and
> > initialised structures.
> >
> > So NACK for this patch as it needs more work if we need this at all.
> >
>
> Hello Sudeep,
>
> Considering a device with several SCMI servers spread over several co-processor
> and possibly also in the Arm TZ secure world, each of these servers
> uses a specific SCMI channel. Without this change, each SCMI protocol gets
> initialized only for the first agent device that is probed.
>

Fair enough, but it also adds complexity. Do you have a master SCMI server
implementation in that case. As some protocols like system might need to
be broadcast to all servers and master server needs to take appropriate
action.

> My setup is also a bit specific. My device has several secure configuration
> features that can individually be enabled or not. For example, configuring
> domain X as secure makes some clocks reachable by Linux only through SCMI,
> and configuring domain Y as secure makes other clocks reachable by Linux
> only through SCMI. For flexibility, I expose domain X resources (here clocks)
> to an Linux agent whereas domain Y resources (here clocks also) are
> exposed to another agent, each agent with its specific transport/channel.
> Enabling each agent node in the Linux FDT allows to define which SCMI clocks
> get exposed and hence registered in the kernel.
> Without the change proposed here, I cannot get the clocks exposed to both
> agents when enabled as the SCMI clock protocol is initialized only for the 1st
> probbed agent device.
>

OK, as Cristian has already mentioned we need to clean up a bit on these
initcalls and Cristian has some WIP patches, I would like to wait and look
at them instead of breaking other usecases with patch(multiple devices
per protocol within one scmi server)

-- 
Regards,
Sudeep

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