Re: [RFC] Separate time support for using cpu timer

[Jun Sun <jsun@mvista.com>]

On Tue, Apr 20, 2004 at 03:41:32PM +0200, Maciej W. Rozycki wrote:
> On Mon, 19 Apr 2004, Jun Sun wrote:
> 
> > Solution
> > --------
> > 
> > All the boards that I am really concerned right now have cpu count/compare
> > registers.  I believe this will even more so in the future.
> > 
> > Therefore I like to propose a separate time support for systems that use
> > cpu timer as their system timer.
> > 
> > As you can see from the patch, the new code is much simpler.
> 
>  It makes it separate again -- more maintenance burden and a bigger
> opportunity to have functional divergence, sigh...
> 

Pretty much true for lots of improvement we made in the past a couple of
years .... :)

>  Additionally I don't think using the CP0 Count & Compare registers for
> the system timer is the way to go.  It's rather a way to escape when
> there's no other possibility.  A lot of systems have a reliable external
> timer interrupt source and using it actually would free the CP0 registers
> for other uses, like profiling or a programmable interval timer.
> 

I was rather neutral on this point until I started to add HRT/VST support to 
MIPS.  When adding such features you really just want one common timer code.
And the best choice for MIPS is cpu timer.

BTW, I plan to submit MIPS/HRT support based on the cpu-timer patch.  Hopefully 
this will catch more attention to the cpu timer patch....

Jun