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Subject: Re: [PATCH 2 1/4] powerpc: drop the ability to tweak SMT mode at
 boot time
From: Scott Wood <scottwood@freescale.com>
To: Michael Ellerman <mpe@ellerman.id.au>
Date: Tue, 9 Dec 2014 15:04:44 -0600
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Cc: linuxppc-dev@lists.ozlabs.org, Greg Kurz <gkurz@linux.vnet.ibm.com>
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On Tue, 2014-12-09 at 15:11 +1100, Michael Ellerman wrote:
> On Fri, 2014-12-05 at 12:52 -0600, Scott Wood wrote:
> > On Fri, 2014-12-05 at 16:14 +0100, Greg Kurz wrote:
> > > The smt-enabled kernel parameter basically leaves unwanted cpus executing
> > > in firmware or wherever they happen to be. The very same applies to the
> > > ibm,smt-enabled DT property which is no more used by anything known. These
> > > are hacks that shoudn't be used in a production environment.
> > > 
> > > Quoting mpe, "there are better ways for firmware to disable SMT".
> > 
> > Those "better ways" don't apply to Freescale chips, where the OS enables
> > (or not) SMT without any interaction with firmware.
> 
> But how does it know there even are SMT threads? From the device tree? So
> just don't present the threads in the device tree?

The device tree is for hardware description, not configuration...

-Scott