[PATCH V3 0/6] ARM64: Add support for FSL's LS2085A SoC

[bhupesh.sharma at freescale.com]

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> -----Original Message-----
> From: Sharma Bhupesh-B45370
> Sent: Tuesday, September 09, 2014 5:16 PM
> To: 'Arnd Bergmann'; Mark Rutland
> Cc: linux-arm-kernel at lists.infradead.org; rob.herring at linaro.org; Catalin
> Marinas; Will Deacon; Yoder Stuart-B08248; grant.likely at secretlab.ca;
> Marc Zyngier; Basu Arnab-B45036; Geoff Levand
> Subject: RE: [PATCH V3 0/6] ARM64: Add support for FSL's LS2085A SoC
> 
> Hi Mark, Arnd
> 
> > -----Original Message-----
> > From: Arnd Bergmann [mailto:arnd at arndb.de]
> > Sent: Thursday, September 04, 2014 3:09 PM
> > To: Mark Rutland
> > Cc: linux-arm-kernel at lists.infradead.org; rob.herring at linaro.org;
> > Sharma Bhupesh-B45370; Catalin Marinas; Will Deacon; Yoder
> > Stuart-B08248; grant.likely at secretlab.ca; Marc Zyngier; Basu
> > Arnab-B45036; Geoff Levand
> > Subject: Re: [PATCH V3 0/6] ARM64: Add support for FSL's LS2085A SoC
> >
> > On Thursday 04 September 2014 10:13:19 Mark Rutland wrote:
> > > On Wed, Sep 03, 2014 at 07:31:44PM +0100, Arnd Bergmann wrote:
> > > > On Wednesday 03 September 2014 17:31:30 Mark Rutland wrote:
> > > > >
> > > > > However, I'm not sure I follow the reasoning for making this
> > > > > significantly harder, and even ignoring that I don't think this
> > > > > does make things significantly harder. Especially so if we have
> > > > > a PSCI node but not an enable method -- in that case its trivial
> > > > > to patch in an unrelated enable-method anyhow.
> > > >
> > > > Right, it's not actually much harder. A better way to look at it
> > > > is probably that we document what which parts we expect to stay
> > > > constant and which parts are to be filled out by the boot loader.
> > > > Independent of what PSCI implementation the boot loader provides,
> > > > we would like to see enable-method="psci".
> > >
> > > So in the /cpus node, have a comment like:
> > >
> > > /*
> > >  * We expect the enable-method to be "psci", but this is dependent
> > > on
> > >  * the FW, which will fill this in.
> > >  */
> >
> > I was thinking of leaving the enable-method in the cpus node, but
> > having an empty psci node with a similar comment.
> >
> > > Or, should we put together a soc-guidance.txt with that, ensuring
> > > things are initialised correctly (CNTVOFF, CNTFREQ), etc?
> >
> > I would very much welcome documentation like that!
> 
> Is this documentation planned (already being worked upon), or should I
> try to spin-out a RFC patch which tries to add this guidance
> documentation.
> 
> Regards,
> Bhupesh
> 
> >
> > > > I just saw that Geoff had a related comment, and documenting this
> > > > would make it clearer to other reviewers, as well as people that
> > > > happen to look at this file as a base for new platforms.
> > >
> > > I agree that having something to point people in the right direction
> > > is a good idea. The only point I disagree with is putitng something
> > > in the DT that can be trivially made false (and possibly with good
> > reason).
> > >
> > > I'm happy with having comments.
> >
> > Right, but I see no good reason for having something else in the
> > enable- method, the only way I can see why that would be done is for
> > the boot loader or firmware implementer to be misinformed.
> >
> > 	Arnd