linux-kernel - Re: [PATCH v1 1/2] remoteproc: dt: Provide bindings for iMX6SX/7D Remote Processor Controller driver

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Date:   Tue, 18 Jul 2017 09:38:15 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Oleksij Rempel <ore@...gutronix.de>
Cc:     Oleksij Rempel <o.rempel@...gutronix.de>,
        devicetree@...r.kernel.org, kernel@...gutronix.de,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        Shawn Guo <shawnguo@...nel.org>,
        Fabio Estevam <fabio.estevam@....com>,
        Ohad Ben-Cohen <ohad@...ery.com>,
        linux-remoteproc@...r.kernel.org, linux@...pel-privat.de
Subject: Re: [PATCH v1 1/2] remoteproc: dt: Provide bindings for iMX6SX/7D
 Remote Processor Controller driver

On Tue 18 Jul 01:45 PDT 2017, Oleksij Rempel wrote:

> Hallo Bjorn,
> 
> On 11.07.2017 00:14, Bjorn Andersson wrote:
> > On Mon 10 Jul 07:42 PDT 2017, Oleksij Rempel wrote:
> > 
> > > Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
> > > ---
> > >  .../devicetree/bindings/remoteproc/imx-rproc.txt   | 44 ++++++++++++++++++++++
> > >  1 file changed, 44 insertions(+)
> > >  create mode 100644 Documentation/devicetree/bindings/remoteproc/imx-rproc.txt
> > > 
> > > diff --git a/Documentation/devicetree/bindings/remoteproc/imx-rproc.txt b/Documentation/devicetree/bindings/remoteproc/imx-rproc.txt
> > > new file mode 100644
> > > index 000000000000..e7c61993e1b8
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/remoteproc/imx-rproc.txt
> > > @@ -0,0 +1,44 @@
> > > +NXP iMX6SX/iMX7D Co-Processor Bindings
> > > +----------------------------------------
> > > +
> > > +This binding provides support for ARM Cortex M4 Co-processor found on some
> > > +NXP iMX SoCs.
> > > +
> > > +Required properties:
> > > +- compatible		Should be one of:
> > > +				"fsl,imx7d-rproc"
> > > +				"fsl,imx6sx-rproc"
> > > +- clocks		Clock for co-processor (See: ../clock/clock-bindings.txt)
> > > +- syscfg		Phandle to syscon block which provide access to
> > 
> > This is called "syscon" in the code and the example.
> 
> done.
> 
> > > +			System Reset Controller
> > > +
> > > +Optional properties:
> > > +- reg:			Should contain the address ranges for some of internal
> > > +			memory regions.
> > 
> > Something less hand-wavy, like: "Should list the memory regions for the
> > remoteproc"
> > 
> > > +- reg-names:		Contains the corresponding names for the memory
> > > +			regions. These should be named "ddr", "ocram", "ocram-s",
> > > +			"ocram-epdc" or "ocram-pxp".
> > 
> > Make this comment define which memory regions are required for each of
> > the systems.
> 
> done.
> 
> > > +Fallowing memory ranges are expected:
> > > +- For "fsl,imx7d-rproc"
> > > +	<0x00900000 0x00020000> - "ocram"
> > > +	<0x00920000 0x00020000> - "ocram-epdc"
> > > +	<0x00940000 0x00008000> - "ocram-pxp"
> > > +	<0x80000000 0x0FFF0000> - "ddr" (code area)
> > > +	<0x80000000 0x60000000> - "ddr" (data area)
> > 
> > There's no reason to list the actual regions in the binding
> > document. Just list the requires regions for each system.
> > 
> > > +- For "fsl,imx6sx-rproc"
> > > +	<0x008F8000 0x00004000> - "ocram-s"
> > > +	<0x80000000 0x0FFF8000> - "ddr" (code area)
> > > +	<0x80000000 0x60000000> - "ddr" (data area)
> > > +
> > > +Note: the "ddr" code and data ranges are overlapping. Code area is smaller
> > > +than data area.  So this range should be carefully chosen according to your
> > > +system and application requirements.
> > > +
> > 
> > This is a source of future issues as this indicates that I should have
> > reg-names list "ddr" twice.
> 
> Then I will name it:
> "ddri" (incstruction/code area),
> "ddrd" (data area)
> 
> unless there are other suggestions.
> 

But are you saying that it's correct that these two memory regions
should overlap?

> > Also, as you warn about the user needing to pick the values for "ddr",
> > does that mean that it's a carveout of System RAM?
> 
> Yes, it is a part of System RAM.
> 

Then there will be an associated reserved-memory region for the
region(s), you should add a label to this and use "memory-region" to get
hold of the addresses instead.

Regards,
Bjorn