On Thu, Jun 11, 2015 at 10:34:15AM -0700, Andy Lutomirski wrote:
> On Thu, Jun 11, 2015 at 7:14 AM, Huang Rui <ray.hu...@amd.com> wrote:
> > MWAITX can enable a timer and a corresponding timer value specified in SW
> > P0 clocks. The SW P0 frequency is the same with TSC. The timer provides an
> > upper bound on how long the instruction waits before exiting.
> >
> > The implementation of delay function in kernel can lerverage the timer of
> > MWAITX. This patch provides a new method (delay_mwaitx) to measure delay
> > time.
> >
> > Suggested-by: Andy Lutomirski <l...@amacapital.net>
> > Suggested-by: Borislav Petkov <b...@suse.de>
> > Suggested-by: Peter Zijlstra <pet...@infradead.org>
> > Signed-off-by: Huang Rui <ray.hu...@amd.com>
> > ---
> > arch/x86/include/asm/mwait.h | 11 +++++++++++
> > arch/x86/lib/delay.c | 41 ++++++++++++++++++++++++++++++++++++++++-
> > 2 files changed, 51 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/include/asm/mwait.h b/arch/x86/include/asm/mwait.h
> > index ece8048..9b41580 100644
> > --- a/arch/x86/include/asm/mwait.h
> > +++ b/arch/x86/include/asm/mwait.h
> > @@ -14,6 +14,8 @@
> > #define CPUID5_ECX_INTERRUPT_BREAK 0x2
> >
> > #define MWAIT_ECX_INTERRUPT_BREAK 0x1
> > +#define MWAITX_ECX_TIMER_ENABLE BIT(1)
> > +#define MWAITX_MAX_LOOPS ((u32)-1)
> >
> > static inline void __monitor(const void *eax, unsigned long ecx,
> > unsigned long edx)
> > @@ -80,4 +82,13 @@ static inline void mwait_idle_with_hints(unsigned long
> > eax, unsigned long ecx)
> > current_clr_polling();
> > }
> >
> > +static inline void mwaitx(unsigned long eax, unsigned long loops,
> > + bool enable)
> > +{
> > + if (enable)
> > + __mwaitx(eax, loops, MWAITX_ECX_TIMER_ENABLE);
> > + else
> > + __mwaitx(eax, 0, 0);
> > +}
>
> What's the purpose of the "enable" parameter?
>
Enable mwaitx timer. Should I add comments to explain the usage?
Thanks,
Rui
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