Re: speedstep-smi woes

[Dominik Brodowski <linux@brodo.de>]

On Tue, Nov 18, 2003 at 08:09:34PM +0100, Ducrot Bruno wrote:
> On Tue, Nov 18, 2003 at 07:20:46PM +0100, Dominik Brodowski wrote:
> > Under heavy load speedstep-smi generates "cpufreq: change failed" messages
> > at least on two systems, one of them my own. I've tried to evaluate how to
> > avoid these failures:
> > 
> > - wbinvd() has no positive effect
> > - disabling bus master arbitration (io-port 0x22 on 440bx) has no positive effect
> > - mdelay(250) immediately before the asm smi call has resulted in _zero_
> >   failures.
> > 
> > However, in most cases, even under heavy load, the speedstep-smi driver
> > _does_ achieve speedstep transitions. 
> > 
> > So, how to proceed?
> > a) Try to avoid these failures, even if the cost of all transitions is 250ms
> >    then? This practically disables dynamic frequency scaling for
> >    speedstep-smi.
> > b) Do the same as before: this means that sometimes the frequency isn't
> >    changed even though the user or the dynamic frequency scaling governor
> >    demands a higher frequency. Also, the "speedstep_init" step tends to fail
> >    sometimes.
> > 
> 
> Have you done testing with ide stuff in pio mode?

No, as I don't want to lose UDMA2. However, it seems to work. Why?

Also, how do we disable DMA safely during a call to speedstep_smi_set_freq()?
kernel/dma.c and include/asm/dma.h neither show a way to "disable" DMA like
it can be done for preempt, irqs, etc. I really don't want to tell users:
disable DMA if you want to use this speedstep driver...

	Dominik