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From: Mathieu Poirier <mathieu.poirier@linaro.org>
Date: Thu, 14 Mar 2024 10:29:51 -0600
Message-ID: <CANLsYkzdfP8Np-XwPDt=GBNLYiSypd8tNdb29KUwr+tyi7gJEA@mail.gmail.com>
Subject: Re: [PATCH 1/3] remoteproc: Add Arm remoteproc driver
To: Sudeep Holla <sudeep.holla@arm.com>
Cc: Abdellatif El Khlifi <abdellatif.elkhlifi@arm.com>, Bjorn Andersson <andersson@kernel.org>, 
	Rob Herring <robh+dt@kernel.org>, Liviu Dudau <liviu.dudau@arm.com>, 
	Lorenzo Pieralisi <lpieralisi@kernel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>, Conor Dooley <conor+dt@kernel.org>, 
	Drew.Reed@arm.com, Adam.Johnston@arm.com, 
	linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, 
	linux-kernel@vger.kernel.org, linux-remoteproc@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"

On Thu, 14 Mar 2024 at 08:59, Sudeep Holla <sudeep.holla@arm.com> wrote:
>
> On Thu, Mar 14, 2024 at 08:52:59AM -0600, Mathieu Poirier wrote:
> > On Wed, Mar 13, 2024 at 05:17:56PM +0000, Abdellatif El Khlifi wrote:
> > > Hi Mathieu,
> > >
> > > On Wed, Mar 13, 2024 at 10:25:32AM -0600, Mathieu Poirier wrote:
> > > > On Tue, Mar 12, 2024 at 05:32:52PM +0000, Abdellatif El Khlifi wrote:
> > > > > Hi Mathieu,
> > > > >
> > > > > On Tue, Mar 12, 2024 at 10:29:52AM -0600, Mathieu Poirier wrote:
> > > > > > > This is an initial patchset for allowing to turn on and off the remote processor.
> > > > > > > The FW is already loaded before the Corstone-1000 SoC is powered on and this
> > > > > > > is done through the FPGA board bootloader in case of the FPGA target. Or by the Corstone-1000 FVP model
> > > > > > > (emulator).
> > > > > > >
> > > > > > >From the above I take it that booting with a preloaded firmware is a
> > > > > > scenario that needs to be supported and not just a temporary stage.
> > > > >
> > > > > The current status of the Corstone-1000 SoC requires that there is
> > > > > a preloaded firmware for the external core. Preloading is done externally
> > > > > either through the FPGA bootloader or the emulator (FVP) before powering
> > > > > on the SoC.
> > > > >
> > > >
> > > > Ok
> > > >
> > > > > Corstone-1000 will be upgraded in a way that the A core running Linux is able
> > > > > to share memory with the remote core and also being able to access the remote
> > > > > core memory so Linux can copy the firmware to. This HW changes are still
> > > > > This is why this patchset is relying on a preloaded firmware. And it's the step 1
> > > > > of adding remoteproc support for Corstone.
> > > > >
> > > >
> > > > Ok, so there is a HW problem where A core and M core can't see each other's
> > > > memory, preventing the A core from copying the firmware image to the proper
> > > > location.
> > > >
> > > > When the HW is fixed, will there be a need to support scenarios where the
> > > > firmware image has been preloaded into memory?
> > >
> > > No, this scenario won't apply when we get the HW upgrade. No need for an
> > > external entity anymore. The firmware(s) will all be files in the linux filesystem.
> > >
> >
> > Very well.  I am willing to continue with this driver but it does so little that
> > I wonder if it wouldn't simply be better to move forward with upstreaming when
> > the HW is fixed.  The choice is yours.
> >
>
> I think Robin has raised few points that need clarification. I think it was
> done as part of DT binding patch. I share those concerns and I wanted to
> reaching to the same concerns by starting the questions I asked on corstone
> device tree changes.
>

I also agree with Robin's point of view.  Proceeding with an initial
driver with minimal functionality doesn't preclude having complete
bindings.  But that said and as I pointed out, it might be better to
wait for the HW to be fixed before moving forward.

> --
> Regards,
> Sudeep