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

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Message-Id: <a1277b1f-f829-4d02-9e54-68ab4faaa047@www.fastmail.com>
Date:   Tue, 09 Feb 2021 18:07:41 -0800
From:   nnet <nnet@...tmail.fm>
To:     Marek Behún <kabel@...nel.org>
Cc:     Pali Rohár <pali@...nel.org>, a.heider@...il.com,
        andrew@...n.ch, gerald@....net, gregory.clement@...tlin.com,
        kostap@...vell.com, linux-arm-kernel@...ts.infradead.org,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        luka.perkov@...tura.hr, miquel.raynal@...tlin.com,
        mturquette@...libre.com, rmk+kernel@...linux.org.uk,
        sboyd@...nel.org, tmn505@...il.com, vladimir.vid@...tura.hr
Subject: Re: [PATCH mvebu v2 00/10] Armada 37xx: Fix cpufreq changing base CPU speed to 800 MHz from 1000 MHz



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@...tmail.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
> > 
> > > 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

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.