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Re: machdep.frequency.current handling incomplete ?


On 20 Jul 2014, at 19:22, Manuel Bouyer <bouyer%antioche.eu.org@localhost> 

> Hello,
> I already noticed that setting machdep.frequency.current to 1000 on the
> beaglebone would cause it to hang, even with an external 5V supply.
> Setting it to 900 used to work (modulo other problems, which are also
> present if I don't change the frequency).
> Now that I have X11 running, I tried glxgears. Up to 800Mhz everything
> is fine, but with glxgears running, switching the frequency to 900Mhz
> causes the same hang. Note that I see this with both my beaglebone and
> beaglebone black, so I don't think I have broken hardware.
> So I wonder if anyone is aware of something missing to properly switch
> the CPU to higher frequencies on the beaglebone ?
> Maybe some voltage adjustement in the SoC, or at the tps65217 level ?

I guess it’s voltage too low for operation at desired frequency. Currently 
tps65217pmic(4) does not support setting the voltage (only reading back), but 
if you compare outputs of envstat(8) when starting NetBSD, while already 
running at different frequency in U-Boot, you’ll notice the voltages are 
slightly different.

I think Dennis Ferguson already wrote about that in the past (circa august-sept 
2013), so please search the mailing list archive.

Best regards,
Radoslaw Kujawa

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