Re: [PATCH v5 11/15] arm64: head.S: Change the register el2_setup() returns its result in x0

[Pavel Machek <pavel@ucw.cz>]

On Thu 2016-02-18 11:41:27, Lorenzo Pieralisi wrote:
> Hi James,
> 
> On Tue, Feb 16, 2016 at 03:49:23PM +0000, James Morse wrote:
> > Today el2_setup() returns its result in w20. This means we can't call it
> > like any normal function. Change this to w0.
> > 
> > All three callers of el2_setup() call set_cpu_boot_mode_flag() immediately
> > afterwards, and don't rely on x0 in later code. Boot cpu code calls
> > preserve_boot_args() before el2_setup(), so we don't clobber the DT pointer.
> > 
> > Signed-off-by: James Morse <james.morse@arm.com>
> > ---
> >  arch/arm64/include/asm/processor.h |  2 ++
> >  arch/arm64/kernel/head.S           | 18 +++++++++---------
> >  2 files changed, 11 insertions(+), 9 deletions(-)
> > 
> > diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
> > index 4acb7ca94fcd..07ac4351538e 100644
> > --- a/arch/arm64/include/asm/processor.h
> > +++ b/arch/arm64/include/asm/processor.h
> > @@ -188,4 +188,6 @@ static inline void spin_lock_prefetch(const void *x)
> >  
> >  void cpu_enable_pan(void *__unused);
> >  
> > +int el2_setup(void);
> 
> Do we really need to have this declaration (and this patch) ? We never
> treat (and call) el2_setup as a C function anyway, as long as the registers
> used to pass in values (and return value) are documented I do not think we
> have an issue anyway, am I missing something here ?

Well, using non-standard calling convention for something that can use
standard one is very ugly at least.

Best regards,
								Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html