linux-kernel - Re: [PATCH 3/5] arm64: refactor delay() to enable polling for value

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Message-ID: <193a81555a87a6d499fbe889406eeb2014465ec5.camel@amazon.com>
Date: Wed, 6 Nov 2024 17:42:38 +0000
From: "Okanovic, Haris" <harisokn@...zon.com>
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Subject: Re: [PATCH 3/5] arm64: refactor delay() to enable polling for value

On Tue, 2024-11-05 at 11:42 -0800, Christoph Lameter (Ampere) wrote:
> CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe.
> 
> 
> 
> On Tue, 5 Nov 2024, Haris Okanovic wrote:
> 
> > -#define USECS_TO_CYCLES(time_usecs)                  \
> > -     xloops_to_cycles((time_usecs) * 0x10C7UL)
> > -
> > -static inline unsigned long xloops_to_cycles(unsigned long xloops)
> > +static inline u64 xloops_to_cycles(u64 xloops)
> >  {
> >       return (xloops * loops_per_jiffy * HZ) >> 32;
> >  }
> > 
> > -void __delay(unsigned long cycles)
> > +#define USECS_TO_XLOOPS(time_usecs) \
> > +     ((time_usecs) * 0x10C7UL)
> > +
> > +#define USECS_TO_CYCLES(time_usecs) \
> > +     xloops_to_cycles(USECS_TO_XLOOPS(time_usecs))
> > +
> 
> 
> > +#define NSECS_TO_XLOOPS(time_nsecs) \
> > +     ((time_nsecs) * 0x10C7UL)
> 
> The constant here is the same value as for microseconds. If I remember
> correctly its 5UL for nanoseconds.
> 

You're right, good catch. Should be `nsecs * 0x5UL` per old code.