linux-kernel - Re: [PATCH] arm64: dts: meson: remove CPU opps below 1GHz for G12B/SM1

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Message-Id: <C70293C2-8CE8-42CE-911A-E0CC3DFB82FC@gmail.com>
Date:   Thu, 10 Feb 2022 05:46:52 +0400
From:   Christian Hewitt <christianshewitt@...il.com>
To:     Kevin Hilman <khilman@...libre.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Neil Armstrong <narmstrong@...libre.com>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: dts: meson: remove CPU opps below 1GHz for
 G12B/SM1


> On 10 Feb 2022, at 5:31 am, Kevin Hilman <khilman@...libre.com> wrote:
> 
> Christian Hewitt <christianshewitt@...il.com> writes:
> 
>> Amlogic G12B and SM1 devices experience CPU stalls and random board
>> wedges when the system idles and CPU cores clock down to lower opp
>> points. Recent vendor kernels include a change to remove 100-250MHz
>> (with no explanation) [0] but other downstream sources also remove
>> the 500/667MHz points (also with no explanation). Unless 100-667Mhz
>> opps are removed or the CPU governor forced to performance, stalls
>> are observed, so let's remove them an improve stability/uptime.
> 
> Just curious: what CPUfreq governor do you use by default for the
> LibreELEC kernel?

LE uses ondemand. One of the original clues on the problem us that the
issue isn’t seen in some of the retro-gaming forks on LE's codebase
which use the performance governor (and overclocks, etc.)

> Your patch greatly improves the stability I'm seeing, but doesn't quite
> elimitate it.
> 
> I'm testing suspend/resume in a loop on VIM3, and with schedutil
> (default) or ondemand, it eventually hangs.  With either powersave or
> performance it's stable.  
> 
> Kevin