Re: [ANNOUNCE] ktimers subsystem

[George Anzinger <george@mvista.com>]

Tim Bird wrote:
> Roman Zippel wrote:
> 
>>On Sun, 25 Sep 2005, Thomas Gleixner wrote:
>>
>>>Can you please point out which architectures do not have a 32x32->64
>>>instruction ?
> 
> 
> <snip>
> 
>>For the rest you might want to check <asm/div64.h>, if div64 has to be 
>>emulated, there are good chances this instruction has to be emulated as 
>>well (especially in smaller embedded archs).
> 
> 
> Hmmm.  In my experience, there are several embedded platforms
> with a 32x32->64 instruction, which are lacking a div64 instruction.
> I don't think checking for div64 is a very good metric here.

Also, even having a div64 instruction does not eliminate the asm/div64.h 
as it checks for results that are >32-bits and does the right thing. 
For example, letting the x86 do this divide with such a result, results 
in a trap.

This is why we need to be very careful where we use the div_ll_l_rem() 
which accesses just this instruction.

-- 
George Anzinger   george@mvista.com
HRT (High-res-timers):  http://sourceforge.net/projects/high-res-timers/