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Re: Stability Under Load


On 08/19/2011 05:48 PM, Marc Dietrich wrote:

It could also be related to power supply. What we do is modifing the
voltage supplies for serveral power sources. I had the feeling, that
Toshiba undervoltaged some CPU supplies in order to save energy (compared
to other boards). So I increased SM1 from 1V to 1.2V which may have been

  How did you do this?

check board-paz00-power.c

  Just looking now. Are you referring to the REGULATOR_INIT macro and
  specifically the line that defines a struct with:

  REGULATOR_INIT(sm1, 725, 1200, true)?

  Are you saying that the default value as provided by Toshiba was

  REGULATOR_INIT(sm1, 725, 1000, true)?

correct. Please understand that these values are just best guesses on what the
Toshiba code does. In fact, kernel 2.6.38 has nothing to do with the original
code base because it's a total rewrite. You may check arch/arm/mach-
tegra/odm_kit/adaptations/pmu/tps6586x/nvodm_pmu_tps6586x.c for reference.

I don't seem to have the arch/arm/mach-tegra/odm_kit directory in the kernel tree I pulled from your git. Where can I get this?

  Have you experienced significant instability with it set to 1000mV? Or
  was this change based on observation what other boards do? I'm wondering
  if the 20% increase in voltage (44% increase in thermal load!) might
  actually push things outside the thermal limits of cooling and thus be
  responsible for contributing to the instability.

No, neither produced problems here, but I haven't make the same stress tests as

OK, I'll try it with 1V instead of 1.2V. Any other changes to voltages from defaults? Is there a way to disable any voltage setting by the kernel to just use whatever is set by default? Would doing so also disable all clocking down for power saving?

It would be nice if you could test a .32 based kernel and see if
it also happens there. Also you could try your new model.

  I haven't tried 2.6.32 because I couldn't find one at the time, but
  I tried the old 2.6.29 and 2.6.38, and the instability on my old
  AC100 was the same. Haven't tried it on the new one yet. Do you think
  2.6.32 could be behaving differently to both of those? If so, why? Where
  can I get the Tegra-patched 2.6.32 kernel?

gitorious.org/ac100? (on the front page)

  I'll try it, but I'm curious to know why you think 2.6.32 might be
  better in this sense than 2.6.29 and 2.6.38.

ah, you tried 2.6.29. I think that's also ok, but 2.6.32 is a bit newer. They
share most of the ac100 specific code, but there my be differences.

I'll try that. Was the 1.2V SM1 change present in these older kernels, too? Or is that a new thing since after 2.6.29?


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