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Re: beaglebone: changing cpu frequency
On Jul 31, 2013, at 11:54 PM, Radoslaw Kujawa
> On 1 Aug 2013, at 3:03 AM, Matt Thomas <matt%3am-software.com@localhost>
>> I still need a good method to get the powersource from the tps65217pmic so
>> I can limit the frequencies when power is limited.
> The power source is checked in the driver, but it's only used to print the
> current source during attachment. The value of this register is never checked
> again later.
> I think we have at least two ways to do it:
> - Make TPS65217 generate an interrupt upon power source change. The interrupt
> line from TPS is connected to NNMI input on Sitara. I'm not really sure if
> it's a good idea to generate interrupt on a line that is labeled "NNMI",
> sounds dangerous (but it's not like I've actually checked what happens if you
> trigger it).
> - Just make an additional sysmon indicator and poll the value of TPS register
> as a part of sysmon refresh in tps65217pmic driver. Then send an event to
> powerd(8) upon change of the power source. Possibly additional
> sensor_powersource should be defined to make this an elegant solution. The
> powerd(8) could react and change CPU speed via script that writes to sysctl.
I think the system should automatically drop cpu speed to 550MHz to be safe.
Then let powerd figure out if it should be increased.
Maybe add a PMFE_POWER_CHANGED event and I can use pmf_event_register to monitor
for it when your driver does a pmf_event_inject with it.
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