Re: [PATCH mvebu v2 00/10] Armada 37xx: Fix cpufreq changing base CPU speed to 800 MHz from 1000 MHz

nnet nnet at fastmail.fm
Wed Feb 10 14:08:59 EST 2021 


On Wed, Feb 10, 2021, at 10:03 AM, Pali Rohár wrote:
> On Wednesday 10 February 2021 09:34:07 nnet wrote:
> > On Wed, Feb 10, 2021, at 1:23 AM, Pali Rohár wrote:
> > > On Tuesday 09 February 2021 18:07:41 nnet wrote:
> > > > On Tue, Feb 9, 2021, at 5:51 PM, nnet wrote:
> > > > > On Tue, Feb 9, 2021, at 5:31 PM, nnet wrote:
> > > > > > On Tue, Feb 9, 2021, at 3:26 PM, Marek Behún wrote:
> > > > > > > On Tue, 09 Feb 2021 15:16:45 -0800
> > > > > > > nnet <nnet at fastmail.fm> wrote:
> > > > > > > 
> > > > > > > > I've two of these and I've just swapped them (and re-pasted the heat sinks).
> > > > > > > > 
> > > > > > > > The second one ran under load for awhile and now has frozen as well.
> > > > > > > > 
> > > > > > > > Under a moderate load `wget -O /dev/null <large.bin>` @X00Mbits they are fine.
> > > > > > > > 
> > > > > > > > Under a 1 min speed test of load ~200Mbits routed WireGuard they freeze.
> > > > > > > > 
> > > > > > > > They fine with both those workloads @1000_800.
> > > > > > > > 
> > > > > > > > Perhaps it's heat? Unfortunately I don't have any numbers on that ATM.
> > > > > > > 
> > > > > > > Try disabling cpufreq in kernel completely, compile boot image at
> > > > > > > 1200 MHz. If it continues freezing, then I fear we can't help you with
> > > > > > > 1200 MHz :(
> > > > > > 
> > > > > > cat /sys/devices/system/cpu/cpufreq/policy0/scaling_available_frequencies 
> > > > > > 200000 300000 600000 1200000 
> > > > > > 
> > > > > > I'm not getting any freezes with 1.2GHz fixed after 20 minutes of load:
> > > > > > 
> > > > > > echo 1200000 > /sys/devices/system/cpu/cpufreq/policy0/scaling_min_freq
> > > > > > 
> > > > > > Setting it back to min 200MHz I get a freeze within a minute:
> > > > > > 
> > > > > > echo 200000 > /sys/devices/system/cpu/cpufreq/policy0/scaling_min_freq
> > > 
> > > Hello! Could you please enable userspace governor during kernel
> > > compilation?
> > > 
> > >     CONFIG_CPU_FREQ_GOV_USERSPACE=y
> > > 
> > > It can be activated via command:
> > > 
> > >     echo userspace > /sys/devices/system/cpu/cpufreq/policy0/scaling_governor
> > > 
> > > After that you can "force" CPU frequency to specific value, e.g.:
> > > 
> > >     echo 1000000 > /sys/devices/system/cpu/cpufreq/policy0/scaling_setspeed
> > > 
> > > I need to know which switch (from --> to freq) cause this system hang.
> > > 
> > > This patch series (via MIN_VOLT_MV_FOR_L0_L1_1GHZ) is fixing only
> > > switching from 500 MHz to 1000 MHz on 1 GHz variant. As only this switch
> > > is causing issue.
> > > 
> > > I have used following simple bash script to check that switching between
> > > 500 MHz and 1 GHz is stable:
> > > 
> > >     while true; do
> > >         echo 1000000 > /sys/devices/system/cpu/cpufreq/policy0/scaling_setspeed;
> > >         echo 500000 > /sys/devices/system/cpu/cpufreq/policy0/scaling_setspeed;
> > >         echo 1000000 > /sys/devices/system/cpu/cpufreq/policy0/scaling_setspeed;
> > >         echo 500000 > /sys/devices/system/cpu/cpufreq/policy0/scaling_setspeed;
> > >     done
> > 
> > echo userspace | tee /sys/devices/system/cpu/cpufreq/policy0/scaling_governor
> > while true; do
> >   echo 1200000 | tee /sys/devices/system/cpu/cpufreq/policy0/scaling_setspeed;
> >   echo 600000 | tee /sys/devices/system/cpu/cpufreq/policy0/scaling_setspeed;
> > done
> > 
> > >> +#define MIN_VOLT_MV_FOR_L0_L1_1GHZ 1108
> > 
> > With 1108 I get a freeze within a minute. The last output to stdout is 600000.
> > 
> > With 1120 it takes a few minutes.
> > 
> > With any of 1225, 1155, 1132 the device doesn't freeze over the full 5 minute load test.
> > 
> > I'm using ondemand now with the above at 1132 without issue so far.
> 
> Great, thank you for testing!
> 
> Can you check if switching between any two lower frequencies 200000
> 300000 600000 is stable?

This is stable using 1132 mV for MIN_VOLT_MV_FOR_L0_L1_1GHZ:

while true; do
  # down
  echo 1200000 | tee /sys/devices/system/cpu/cpufreq/policy0/scaling_setspeed;
  echo 600000 | tee /sys/devices/system/cpu/cpufreq/policy0/scaling_setspeed;
  echo 300000 | tee /sys/devices/system/cpu/cpufreq/policy0/scaling_setspeed;
  echo 200000 | tee /sys/devices/system/cpu/cpufreq/policy0/scaling_setspeed;
  # up
  echo 300000 | tee /sys/devices/system/cpu/cpufreq/policy0/scaling_setspeed;
  echo 600000 | tee /sys/devices/system/cpu/cpufreq/policy0/scaling_setspeed;
  echo 1200000 | tee /sys/devices/system/cpu/cpufreq/policy0/scaling_setspeed;
  # all down
  echo 200000 | tee /sys/devices/system/cpu/cpufreq/policy0/scaling_setspeed;
  # all up
  echo 1200000 | tee /sys/devices/system/cpu/cpufreq/policy0/scaling_setspeed;
  # almost down
  echo 300000 | tee /sys/devices/system/cpu/cpufreq/policy0/scaling_setspeed;
done    

> > >> Update the CPU voltage value for loads L0 and L1 accordingly when base
> > >> frequency is 1000 or 1200 MHz. The minimal value is updated from the
> > >> original 1.05V to 1.108V.
> > 
> > Perhaps similiar to how a minimum of 1108 mV is useful when shifting to 1GHz, using a minimum of 1132 is useful when shifting to 1.2GHz.
> 
> Maybe... We can only wait if Marvell provide some details about this
> issue.
> 
> > > (of course on 1.2 GHz variant you need to adjust values as only
> > > following frequencies 200000 300000 600000 1200000 are supported)
> > > 
> > > > > > > Marek
> > > > > > >
> > > > > 
> > > > > > +#define MIN_VOLT_MV_FOR_L0_L1_1GHZ 1108
> > > > > 
> > > > > Based on the below at boot time might an equivalent of the above need 
> > > > > to be 1225 for 1.2GHz?
> > > > > 
> > > > > 1200_750
> > > > > SVC REV: 5, CPU VDD voltage: 1.225V
> > > > > 
> > > > > 1000_800
> > > > > SVC REV: 5, CPU VDD voltage: 1.108V
> > > 
> > > This value is printed in WTMI avs.c by following code:
> > > 
> > >     shift = OTP_SVC_SPEED_1000_OFF;
> > >     (OR)
> > >     shift = OTP_SVC_SPEED_1200_OFF;
> > > 
> > >     vdd_otp = ((otp_data[OTP_DATA_SVC_SPEED_ID] >> shift) +
> > >                 AVS_VDD_BASE) & AVS_VDD_MASK;
> > >     regval |= (vdd_otp << HIGH_VDD_LIMIT_OFF);
> > >     regval |= (vdd_otp << LOW_VDD_LIMIT_OFF);
> > >     printf("SVC REV: %d, CPU VDD voltage: %s\n", svc_rev,
> > >             avis_dump[vdd_otp].desc);
> > > 
> > > So voltage value is read from the OTP memory.
> > > 
> > > But I do not know what this value means.
> 
> Link to code: 
> https://github.com/MarvellEmbeddedProcessors/A3700-utils-marvell/blob/master/wtmi/sys_init/avs.c
> 
> You can read this OTP memory (otp_data[] array) in U-Boot by command:
> 
>     md d0012604 1; md d0012604 1; md d0012604 1

=> md d0012604 1; md d0012604 1; md d0012604 1
d0012604: 2b417501                               .uA+
d0012604: 0000945b                               [...
d0012604: 00000000                               ....

> > > > I did this for a quick test for 1.2GHz:
> > > > 
> > > > +#define MIN_VOLT_MV_FOR_L0_L1_1GHZ 1225
> > > > 
> > > > This is working well so far. Frequency is shifting up/down with load applied/stopped.
> > >
>

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