Re: [PATCH v2] drivers: firmware: psci: unify enable-method binding on ARM {64,32}-bit systems

[Mark Rutland <mark.rutland-5wv7dgnIgG8@public.gmane.org>]

On Tue, Apr 26, 2016 at 12:49:00PM +0200, Arnd Bergmann wrote:
> On Tuesday 26 April 2016 11:42:58 Sudeep Holla wrote:
> > On 22/04/16 16:18, Sudeep Holla wrote:
> > > Currently ARM CPUs DT bindings allows different enable-method value for
> > > PSCI based systems. On ARM 64-bit this property is required and must be
> > > "psci" while on ARM 32-bit systems this property is optional and must
> > > be "arm,psci" if present.
> > >
> > > However, "arm,psci" has always been the compatible string for the PSCI
> > > node, and was never intended to be the enable-method. So this is a bug
> > > in the binding and not a deliberate attempt at specifying 32-bit
> > > differently.
> > >
> > > This is problematic if 32-bit OS is run on 64-bit system which has
> > > "psci" as enable-method rather than the expected "arm,psci".
> > >
> > > So let's unify the value into "psci" and remove support for "arm,psci"
> > > before it finds any users.
> > >
> > > Reported-by: Soby Mathew <Soby.Mathew-5wv7dgnIgG8@public.gmane.org>
> > > Cc: Rob Herring <robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> > > Acked-by: Mark Rutland <mark.rutland-5wv7dgnIgG8@public.gmane.org>
> > > Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi-5wv7dgnIgG8@public.gmane.org>
> > > Signed-off-by: Sudeep Holla <sudeep.holla-5wv7dgnIgG8@public.gmane.org>
> > > ---
> > >   Documentation/devicetree/bindings/arm/cpus.txt | 1 -
> > >   drivers/firmware/psci.c                        | 2 +-
> > >   2 files changed, 1 insertion(+), 2 deletions(-)
> > >
> > > v2->v1:
> > >       - Added Mark and Lorenzo's ACKs
> > >       - Updated commit message to specify that it also conflicts with
> > >         PSCI compatible(from Mark's reply on the thread)
> > >
> > > Hi ARM-SoC guys,
> > >
> > > Can you please pick up this single fix for PSCI binding/driver for v4.6 ?
> > >
> > 
> > Gentle ping to include this in next round of arm-soc fixes. It would be
> > good to get this fixed before v4.6 as we don't want to have user of the
> > binding which we want to remove in the release.
> > 
> 
> Applied to the fixes branch. I have to admit that I don't understand
> how the compatible string is really used here, so I have to trust that
> this cannot break any existing machine.

The buggy code was merged for v4.6-rc1, so this hasn't been in a
release, and should not break an existing user.

No compatible string is used here, which is precisely the confusion this
addresses. The PSCI enable-method != the compatible string for a PSCI
node, but the two got confused in a documentation patch, and then that
confusion spread to code.

Thanks,
Mark.
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