On Tuesday 30 March 2004 23:48, Pete Popov wrote:
> Bob Lees wrote:
> >On Tuesday 30 March 2004 22:56, Dan Malek wrote:
> >>Bob Lees wrote:
> >> > ....I suspect I am
> >>>missing something somewhere, but I can't find any references to cpu
> >>> speed control for the MIPS processors, specically the au1x range.
> >>The Au1xxx has a PLL that multiplies the incoming 12 MHz clock up to the
> >>internal frequency. Just be aware there are lots of peripheral clocks
> >>and bus clocks derived from this internal frequency. There is code
> >>in the kernel power management to allow changing the frequency during
> >>operation of Linux, but I don't know how well it works today as I have
> >>not tested that for quite some time.
> >> -- Dan
> >Thanks Dan & Pete for the prompt response.
> >I have tried the /proc/sys/pm/freq interface and by putting a bogomips
> > calc into power.c, it appears to indicate a change in core frequency. I
> > think your caution may be well founded as I got input overruns on the
> > serial console when I took the speed down to 84MHz, good character
> > recognition though, so it was an input buffer speed issue.
> >Also I can see an approx 40-50mA change in current from 84 to 396MHz which
> >indicates something is changing. Supply is at 5 volts thru a simple
> > switcher down to 3.3 volts on the Aurora board. This is with nothing
> > else running and an nfs filesystem. As part of monitoring current I am
> > seeing an anomoly: namely after boot is complete and system is quiesent,
> > at apparently 396MHz, the current is 200mA, now after playing with the
> > freq control the current at 396MHz stabalises at around 250mA. Verrry
> > strange - any thoughts??
> Is the 250mA after you've done a new power cycle, which doesn't make
> sense, or after you scale down to 84 and back up to 396MHz?
After I scale down to 84 and back up to 396MHz. Having seen Dan's comments
which I largely agree with I may not play with the speed after all!! Having
said that I would like to find out why we are seeing this behaviour. It
could well be that the frequency switching is disrupting one of the clocks
and/or the PM which is running on power up.
We already recognise that the peripherals play as much if not a greater part
in the overall power consumption.
> >On another topic, what state is the IRDA driver in?
> It works. Check out the IrDA readme on
> linux-mips.org:/pub/linux/mips/people/ppopov/2.4. I've tested two boards
> back to back using the network layer at FIR speeds, and a board to palm
> pilot using SIR. It's all in the readme.
OK I have this and will have a play.
> >This is building from the
> >patched 2.4.25 kernel on your site Dan. And a big thank you for this
> > source of a patched kernel and build tools.