[Letux-kernel] 1.5GHz problems

H. Nikolaus Schaller hns at goldelico.com
Tue Aug 2 08:34:07 CEST 2016


> Am 02.08.2016 um 01:42 schrieb Grazvydas Ignotas <notasas at gmail.com>:
> On Mon, Aug 1, 2016 at 12:37 AM, H. Nikolaus Schaller <hns at goldelico.com> wrote:
>> B) Pyra: LEDs seem to be blinking slightly irregular @500 MHz only boot (may be harmless)
>> Sometimes the serial console appears to show delays (looks as if some IRQ blocking process runs a little slow?)
>> C) 5432EVM (letux-4.7.0 w/o Pyra Mainboard connected)
>> I have modified the DT so that it also has 500 / 750 / 1250 MHz OPPs like for the Pyra.
>> Termperature measurements (with cooling fingers installed)
> 500 was removed by TI, I guess there was some reason for that. 750 and
> 1250 were fabricated by you, not from some TI data, right?


Theoretically any intermediate point should work...

> For uEVM
> stability testing I'd remove the "unofficial" frequencies, there could
> be some problems we don't know about, and uEVM has been always rock
> stable with the defaults (1 and 1.5 GHz only) for me.

It had been stable until some months ago. At least in my anecdotical memory.

But shouldn't these points be completely ignored if we use the powersave / userspace

I see 0% useage by cpufreq-info for all points except the one that was booted.

And for the 1GHz boot I had removed the 500 & 750 entries.

>> And it might be that we have too much noise on VDD_MPU @1.5GHz.
>> This is now a test scenario that I can compare to the EVM as soon as I find time for doing that.
> Looking forward to that, I hope it will give some hints.
>> Anyways these results now need some interpretation. Especially why VSSYS goes down
>> from 3.6V to 3.5V! And the other voltages remain the same. This either means that the
>> Palmas draws even more current from VSYS - or the bq24297 has reset itself to the default
>> 3.5V regulation mode. Or something else?
> But 3.5V is still in spec, right?

Yes: 3.2 - 4.2V

The change itself is more interesting. Because it is a regulated voltage and the regulator
is inside the bq24297. It can be programmed in 100mV steps.

> Maybe it would it be possible to mod the board to feed VSYS from some
> strong lab supply?

That is on my to-do list... Needs some careful setup since I must reduce the risk
to damage anything to 0%.


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