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Date:   Thu, 16 Jul 2020 12:43:04 -0700 (PDT)
From:   Stefano Stabellini <stefano.stabellini@xilinx.com>
To:     Mathieu Poirier <mathieu.poirier@linaro.org>
cc:     Rob Herring <robh@kernel.org>, Suman Anna <s-anna@ti.com>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Lokesh Vutla <lokeshvutla@ti.com>,
        linux-remoteproc@vger.kernel.org, devicetree@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        stefanos@xilinx.com, BLEVINSK@xilinx.com, tomase@xilinx.com
Subject: Re: [PATCH v2 1/4] dt-bindings: remoteproc: Add bindings for R5F
 subsystem on TI K3 SoCs
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On Thu, 16 Jul 2020, Mathieu Poirier wrote:
> Hi Rob,
> 
> On Tue, Jul 14, 2020 at 11:15:53AM -0600, Rob Herring wrote:
> > On Mon, Jun 29, 2020 at 09:49:19PM -0500, Suman Anna wrote:
> > > The Texas Instruments K3 family of SoCs have one or more dual-core
> > > Arm Cortex R5F processor subsystems/clusters (R5FSS). The clusters
> > > can be split between multiple voltage domains as well. Add the device
> > > tree bindings document for these R5F subsystem devices. These R5F
> > > processors do not have an MMU, and so require fixed memory carveout
> > > regions matching the firmware image addresses. The nodes require more
> > > than one memory region, with the first memory region used for DMA
> > > allocations at runtime. The remaining memory regions are reserved
> > > and are used for the loading and running of the R5F remote processors.
> > > The R5F processors can also optionally use any internal on-chip SRAM
> > > memories either for executing code or using it as fast-access data.
> > > 
> > > The added example illustrates the DT nodes for the single R5FSS device
> > > present on K3 AM65x family of SoCs.
> > > 
> > > Signed-off-by: Suman Anna <s-anna@ti.com>
> > > ---
> > > v2:
> > >  - Renamed "lockstep-mode" property to "ti,cluster-mode"
> > 
> > I don't think that's a move in the right direction given this is at 
> > least partially a standard feature.
> > 
> > As I said before, I'm very hesistant to accept anything here given I 
> > know the desires and activity to define 'system Devicetrees' of which 
> > TI is participating. While maybe an rproc node is sufficient for a 
> > DSP, it seems multiple vendors have R cores and want to define them in 
> > system DT.
> > 
> > Though the system DT effort has not yet given any thought to what is the 
> > view of one processor or instance to another instance (which is what 
> > this binding is). We'll still need something defined for that, but I'd 
> > expect that to be dependent on what is defined for system DT.
> 
> Efforts related to the definition of the system DT are under way, something I
> expect to keep going on for some time to come.  I agree with the need to use the
> system DT to define remote processors and I look forward to the time we can do
> so.

I'll take this opportunity to add that I should be able to publicly
present a System Device Tree proposal for this during the next call (the
next one after the call early next week that has already a full agenda.)


> That being said we need to find a concensus on how to move forward with patches
> that are ready to be merged.  What is your opinion on that?

In my opinion we don't have to necessarily wait for System Device Tree
to make progress with those if they look OK.