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. > >> > >>Thanks. > >> -- 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. > > Pete Bob
