[Soekris] Power management on a Net4801

[Ted Phelps]

Ted Phelps writes:
> I've had a look at the SC1100 data book and it looks like the CPU
> _should_ support suspend modulation (apparently the GX1 is the
> processor module in an SC1100), but when I try to load the gx-suspmod
> module I get a 'No such device' error.  I think the gx_detect_chipset
> function may have gotten broken somewhere along the line.  I'll
> investigate further and report back.

Reporting back...

I can make gx-suspmod.ko load with a fairly minimal patch to tell it to
look for the PCI_VENDOR_ID_NS/PCI_DEVIEC_ID_NS_SC1100_BRIDGE device (if
you try this at home, you'll need to tweak gx_set_cpuspeed to set the
parameters for this device), which is where the suspend modulation
configuration parameters live on the SC1100.  Unfortunately, it seems to
have no effect -- the CPU temperature is unchanged and processes run
just as quickly as they do without the setting.  I've even tried
fiddling the PCI configuration registers by hand with setpci without any
observable result.

If you'd like to judge for yourself, you can try the following without
any compilation or module reloading (see the SC1100 databook, pages 148,
185 and 194-195 for what the magic numbers mean):


Run something that takes a while to run:

> time factor 1341094821421123
1341094821421123: 1341094821421123
8.32user 0.02system 0:08.35elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+178minor)pagefaults 0swaps


Enable power management and other related bits:

> setpci -d 100b:0510 80=7

Set the modulation cycle to 320us on, 320us off:

> setpci -d 100b:0510 94.w=1010

Enable suspend modulation:

> setpci -d 100b:0510 96=1


Re-run the time test to see that nothing has changed:

> time factor 1341094821421123 
1341094821421123: 1341094821421123 
8.26user 0.01system 0:08.26elapsed 100%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+179minor)pagefaults 0swaps


Does anyone see any changes?  Does anyone have a way of monitoring the
power consumption of their net 4801 and is willing to give this a go?

Cheers,
-Ted