On 1 Aug, 2013, at 19:32 , John Klos <john%ziaspace.com@localhost> wrote:
>>> When trying 1000 MHz, the BeagleBone Black locks up and isn't responsive
>>> either on the network or via serial.
>>
>> What power source? I have a 4A (2500ma) 5V supply.
>
> My power supply is a 3 amp unit with a nice, thick cable. I'll try a
> different one and see if it makes a difference.
>
> At 550 MHz, the voltage measured off the power connector is 5.11 volts. At
> 900 MHz with the CPU at 100%, it's 5.11 volts. With the other power supply,
> it's 5.13 volts.
>
> Maybe my BBB is broken - it won't go to 1000 MHz and it's already reporting
> bad sectors in the built-in flash. Sigh.
I don't think it is broken. The one I'm trying hangs when attempting to
set it to 1000 MHz too, and setting it to 900 MHz seems to cause faults like
data_abort_handler: data_aborts fsr=0x1 far=0x801031e
data_abort_handler: data_aborts fsr=0x1 far=0x40467765
which really shouldn't be happening. I can make those errors go away
by configuring a clock ramp for the PLL, but 1000 MHz still doesn't
work and I don't trust that this really fixes anything at 900 MHz
either.
Peaking at what Linux does, every time it alters the MPU frequency it
also considers changing the output of the MPU's voltage regulator in the
tps65217 pmic (before a frequency increase and after a decrease).
The configuration for the BB Black looks like
/*
* To consider voltage drop between PMIC and SoC,
* tolerance value is reduced to 2% from 4% and
* voltage value is increased as a precaution.
*/
operating-points = <
/* kHz uV */
1000000 1350000
800000 1300000
600000 1112000
300000 969000
>;
while the BB looks like
/*
* To consider voltage drop between PMIC and SoC,
* tolerance value is reduced to 2% from 4% and
* voltage value is increased as a precaution.
*/
operating-points = <
/* kHz uV */
/* ES 2.0 Nitro and Turbo OPPs"
1000000 1350000
800000 1300000
*/
720000 1285000
600000 1225000
500000 1125000
275000 1125000
>;
voltage-tolerance = <2>; /* 2 percentage */
clock-latency = <300000>; /* From omap-cpufreq driver */
Assuming the regulator is still set to its reset value (1.100 V according
to the data sheet) after booting, the 520 MHz the BB Black comes out of the
bootstrap at is about the right frequency for that voltage. It may not be safe
to run much too higher than that without the voltage adjustment, though
I guess some parts might be more tolerant of a sag then others.
Dennis Ferguson
Attachment:
signature.asc
Description: Message signed with OpenPGP using GPGMail