Re: [RFC PATCH] ARM: Add imprecise abort enable/disable macro

[Fabrice Gasnier]

On 02/10/2014 10:00 AM, Ben Dooks wrote:
> On 10/02/14 08:50, Fabrice Gasnier wrote:
> > On 02/07/2014 06:09 PM, Will Deacon wrote:
> > > On Fri, Feb 07, 2014 at 04:19:15PM +0000, Fabrice GASNIER wrote:
> > > > This patch adds imprecise abort enable/disable macros.
> > > > It also enables imprecise aborts when starting kernel.
> > > >
> > > > Signed-off-by: Fabrice Gasnier <fabrice.gasnier@xxxxxx>
> > > > ---
> > > >   arch/arm/include/asm/irqflags.h |   33
> > > > +++++++++++++++++++++++++++++++++
> > > >   arch/arm/kernel/smp.c           |    1 +
> > > >   arch/arm/kernel/traps.c         |    4 ++++
> > > >   3 files changed, 38 insertions(+)
> > > >
> > > > diff --git a/arch/arm/include/asm/irqflags.h
> > > > b/arch/arm/include/asm/irqflags.h
> > > > index 3b763d6..82e3834 100644
> > > > --- a/arch/arm/include/asm/irqflags.h
> > > > +++ b/arch/arm/include/asm/irqflags.h
> > > > @@ -51,6 +51,9 @@ static inline void arch_local_irq_disable(void)
> > > >   #define local_fiq_enable()  __asm__("cpsie f    @ __stf" : : :
> > > > "memory", "cc")
> > > >   #define local_fiq_disable() __asm__("cpsid f    @ __clf" : : :
> > > > "memory", "cc")
> > > > +
> > > > +#define local_abt_enable()  __asm__("cpsie a    @ __sta" : : :
> > > > "memory", "cc")
> > > > +#define local_abt_disable() __asm__("cpsid a    @ __cla" : : :
> > > > "memory", "cc")
> > > >   #else
> > > >   /*
> > > > @@ -130,6 +133,36 @@ static inline void arch_local_irq_disable(void)
> > > >       : "memory", "cc");                    \
> > > >       })
> > > > +/*
> > > > + * Enable Aborts
> > > > + */
> > > > +#define local_abt_enable()                    \
> > > > +    ({                            \
> > > > +        unsigned long temp;                \
> > > > +    __asm__ __volatile__(                    \
> > > > +    "mrs    %0, cpsr        @ sta\n"        \
> > > > +"    bic    %0, %0, %1\n"                    \
> > > > +"    msr    cpsr_c, %0"                    \
> > > > +    : "=r" (temp)                        \
> > > > +    : "r" (PSR_A_BIT)                    \
> > > Can you use "i" instead of a register for this constant?
> > Hi,
> >
> > Sure, I will change it in a future patch.
> > > > +    : "memory", "cc");                    \
> > > You don't need the "cc" clobber.
> > That surprises me: I think "orr" and "bic" instruction might change N
> > and Z bits, depending on the result.
> > So shouldn't "cc" be placed here ?
> > I also see that it is used in local_fiq_enable/disable macros just
> > above, that are similar:
>
> No, only if they have the S flag set on the instruction (ORRS,BICS)
Thank you for pointing that out!


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