Re: Fwd: Re: [PATCH] linux-2.5.54_delay-cleanup_A0

[john stultz]

>  Hi!

Hey! Hmm. Odd, this email never got to me directly, instead I found it
through lkml. Hopefully my mail isn't bouncing somewhere...
 

>  > +static void delay_pit(unsigned long loops)
>  > +{
>  > +    int d0;
>  > +    __asm__ __volatile__(
>  > +            "\tjmp 1f\n"
>  > +            ".align 16\n"
>  > +            "1:\tjmp 2f\n"
>  > +            ".align 16\n"
>  > +            "2:\tdecl %0\n\tjns 2b"
>  > +            :"=&a" (d0)
>  > +            :"0" (loops));
>  > +}
>  > +
>  
>  But... this is not using pit to do the delay, right? It is sensitive
>  to CPU clock changes, pit-delay should not be.

You're right, basically I took the previous __loop_delay() and
__rtsc_delay() and moved them to delay_pit() and delay_tsc(),
respectively. I guess the naming is somewhat confusing, but since this
was meant as just a cleanup, I'm trying to use the same code in the same
conditions.(ie: when using the PIT time-source, use the loop delay. when
using the TSC time-source, use the TSC delay). A changing the name or a
comment explaining it would def clear that up. 

You do bring up an interesting idea: actually using the PIT to do
__delay. I think its possible, but not really worth it, as the PIT is
such a nasty bit of hardware to deal with. I'd guess that just reading
the PIT would likely delay for more time then what was actually
requested.

Thanks for the feedback!
-john