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Date:   Wed, 10 Feb 2021 09:34:07 -0800
From:   nnet <nnet@fastmail.fm>
To:     =?UTF-8?Q?Pali_Roh=C3=A1r?= <pali@kernel.org>
Cc:     =?UTF-8?Q?Marek_Beh=C3=BAn?= <kabel@kernel.org>,
        a.heider@gmail.com, andrew@lunn.ch, gerald@gk2.net,
        gregory.clement@bootlin.com, kostap@marvell.com,
        linux-arm-kernel@lists.infradead.org, linux-clk@vger.kernel.org,
        linux-kernel@vger.kernel.org, luka.perkov@sartura.hr,
        miquel.raynal@bootlin.com, mturquette@baylibre.com,
        rmk+kernel@armlinux.org.uk, sboyd@kernel.org, tmn505@gmail.com,
        vladimir.vid@sartura.hr
Subject: =?UTF-8?Q?Re:_[PATCH_mvebu_v2_00/10]_Armada_37xx:_Fix_cpufreq_changing_b?=
 =?UTF-8?Q?ase_CPU_speed_to_800_MHz_from_1000_MHz?=
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On Wed, Feb 10, 2021, at 1:23 AM, Pali Roh=C3=A1r 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 Beh=C3=BAn wrote:
> > > > > On Tue, 09 Feb 2021 15:16:45 -0800
> > > > > nnet <nnet@fastmail.fm> wrote:
> > > > >=20
> > > > > > I've two of these and I've just swapped them (and re-pasted =
the heat sinks).
> > > > > >=20
> > > > > > The second one ran under load for awhile and now has frozen =
as well.
> > > > > >=20
> > > > > > Under a moderate load `wget -O /dev/null <large.bin>` @X00Mb=
its they are fine.
> > > > > >=20
> > > > > > Under a 1 min speed test of load ~200Mbits routed WireGuard =
they freeze.
> > > > > >=20
> > > > > > They fine with both those workloads @1000_800.
> > > > > >=20
> > > > > > Perhaps it's heat? Unfortunately I don't have any numbers on=
 that ATM.
> > > > >=20
> > > > > 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 :(
> > > >=20
> > > > cat /sys/devices/system/cpu/cpufreq/policy0/scaling_available_fr=
equencies=20
> > > > 200000 300000 600000 1200000=20
> > > >=20
> > > > I'm not getting any freezes with 1.2GHz fixed after 20 minutes o=
f load:
> > > >=20
> > > > echo 1200000 > /sys/devices/system/cpu/cpufreq/policy0/scaling_m=
in_freq
> > > >=20
> > > > Setting it back to min 200MHz I get a freeze within a minute:
> > > >=20
> > > > echo 200000 > /sys/devices/system/cpu/cpufreq/policy0/scaling_mi=
n_freq
>=20
> Hello! Could you please enable userspace governor during kernel
> compilation?
>=20
>     CONFIG_CPU_FREQ_GOV_USERSPACE=3Dy
>=20
> It can be activated via command:
>=20
>     echo userspace > /sys/devices/system/cpu/cpufreq/policy0/scaling_g=
overnor
>=20
> After that you can "force" CPU frequency to specific value, e.g.:
>=20
>     echo 1000000 > /sys/devices/system/cpu/cpufreq/policy0/scaling_set=
speed
>=20
> I need to know which switch (from --> to freq) cause this system hang.=

>=20
> 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 swit=
ch
> is causing issue.
>=20
> I have used following simple bash script to check that switching betwe=
en
> 500 MHz and 1 GHz is stable:
>=20
>     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_gov=
ernor
while true; do
  echo 1200000 | tee /sys/devices/system/cpu/cpufreq/policy0/scaling_set=
speed;
  echo 600000 | tee /sys/devices/system/cpu/cpufreq/policy0/scaling_sets=
peed;
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 6=
00000.

With 1120 it takes a few minutes.

With any of 1225, 1155, 1132 the device doesn't freeze over the full 5 m=
inute load test.

I'm using ondemand now with the above at 1132 without issue so far.

>> Update the CPU voltage value for loads L0 and L1 accordingly when bas=
e
>> 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.

> (of course on 1.2 GHz variant you need to adjust values as only
> following frequencies 200000 300000 600000 1200000 are supported)
>=20
> > > > > Marek
> > > > >
> > >=20
> > > > +#define MIN_VOLT_MV_FOR_L0_L1_1GHZ 1108
> > >=20
> > > Based on the below at boot time might an equivalent of the above n=
eed=20
> > > to be 1225 for 1.2GHz?
> > >=20
> > > 1200_750
> > > SVC REV: 5, CPU VDD voltage: 1.225V
> > >=20
> > > 1000_800
> > > SVC REV: 5, CPU VDD voltage: 1.108V
>=20
> This value is printed in WTMI avs.c by following code:
>=20
>     shift =3D OTP_SVC_SPEED_1000_OFF;
>     (OR)
>     shift =3D OTP_SVC_SPEED_1200_OFF;
>=20
>     vdd_otp =3D ((otp_data[OTP_DATA_SVC_SPEED_ID] >> shift) +
>                 AVS_VDD_BASE) & AVS_VDD_MASK;
>     regval |=3D (vdd_otp << HIGH_VDD_LIMIT_OFF);
>     regval |=3D (vdd_otp << LOW_VDD_LIMIT_OFF);
>     printf("SVC REV: %d, CPU VDD voltage: %s\n", svc_rev,
>             avis_dump[vdd_otp].desc);
>=20
> So voltage value is read from the OTP memory.
>=20
> But I do not know what this value means.
>=20
> > I did this for a quick test for 1.2GHz:
> >=20
> > +#define MIN_VOLT_MV_FOR_L0_L1_1GHZ 1225
> >=20
> > This is working well so far. Frequency is shifting up/down with load=
 applied/stopped.
>