Am 25.11.2016 um 13:35 schrieb H. Nikolaus Schaller <hns@goldelico.com>:
I have done this test by soldering a wire to the PALMAS SMPS123 outputs
and connecting an oscilloscope:
<DSC02725.jpeg>
We clearly see that the voltages change (I did start in idle and type
"apt-get update" and ENTER).
Voltages are quite exactly what I have defined in the OPP DT, i.e. 840/880mV going
up to 1100mV.
What you also can see is such voltage steps occur not faster than
every 300ms.
There is some noise on the supply line but that can be an artifact
of the setup and the oscilloscope precision (8bit).
What I have planned to do is a similar test with 1.25GHz and high-load
loops.
For NEON-loop (still at 1GHz max.) I was able to capture a nice picture:
Interestingly we can even underclock the OMAP5 down to 250 MHz and it appears
to run stable as well.
root@letux:~# cpufreq-info
cpufrequtils 008: cpufreq-info (C) Dominik Brodowski 2004-2009
Report errors and bugs to cpufreq@vger.kernel.org, please.
analyzing CPU 0:
driver: cpufreq-dt
CPUs which run at the same hardware frequency: 0 1
CPUs which need to have their frequency coordinated by software: 0 1
maximum transition latency: 350 us.
hardware limits: 250 MHz - 1000 MHz
available frequency steps: 250 MHz, 500 MHz, 750 MHz, 1000 MHz
available cpufreq governors: conservative, userspace, powersave, ondemand, performance
current policy: frequency should be within 250 MHz and 1000 MHz.
The governor "ondemand" may decide which speed to use
within this range.
current CPU frequency is 250 MHz (asserted by call to hardware).
cpufreq stats: 250 MHz:81.74%, 500 MHz:12.91%, 750 MHz:2.24%, 1000 MHz:3.11% (516)
analyzing CPU 1:
driver: cpufreq-dt
CPUs which run at the same hardware frequency: 0 1
CPUs which need to have their frequency coordinated by software: 0 1
maximum transition latency: 350 us.
hardware limits: 250 MHz - 1000 MHz
available frequency steps: 250 MHz, 500 MHz, 750 MHz, 1000 MHz
available cpufreq governors: conservative, userspace, powersave, ondemand, performance
current policy: frequency should be within 250 MHz and 1000 MHz.
The governor "ondemand" may decide which speed to use
within this range.
current CPU frequency is 250 MHz (asserted by call to hardware).
cpufreq stats: 250 MHz:81.74%, 500 MHz:12.91%, 750 MHz:2.24%, 1000 MHz:3.11% (516)
root@letux:~#
This was done with these OPP:
&cpu0 {
operating-points = <
/* kHz uV */
250000 800000
500000 850000
750000 950000
1000000 1050000
// 1250000 1150000
// 1500000 1250000
// 1700000 1250000
>;
};
As you can see I plan to run a slightly lowered 1.25GHz OPP voltage to
be linear between 500 MHz and 1500 MHz.
Am 24.11.2016 um 01:05 schrieb Grazvydas Ignotas <notasas@gmail.com>:
Not that I know of, only Nikolaus can measure it directly.
GraÅžvydas
On Thu, Nov 24, 2016 at 1:42 AM, Michael Mrozek
<EvilDragon@openpandora.org> wrote:
Am Thu, 24 Nov 2016 00:45:07 +0200 hat Grazvydas Ignotas
<notasas@gmail.com> geschrieben:
Hi,
is there an easy way to read out the REAL voltage?
So I can see that the setting really is doing something?
BR,
Nikolaus
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