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Subject: Re: [PATCH] arm64: dts: meson: remove CPU opps below 1GHz for
 G12B/SM1
From:   Christian Hewitt <christianshewitt@gmail.com>
In-Reply-To: <7h7da3o6cg.fsf@baylibre.com>
Date:   Thu, 10 Feb 2022 05:46:52 +0400
Cc:     Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Neil Armstrong <narmstrong@baylibre.com>,
        devicetree <devicetree@vger.kernel.org>,
        linux-arm-kernel@lists.infradead.org,
        linux-amlogic@lists.infradead.org, linux-kernel@vger.kernel.org
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Message-Id: <C70293C2-8CE8-42CE-911A-E0CC3DFB82FC@gmail.com>
References: <20220209135535.29547-1-christianshewitt@gmail.com>
 <7h7da3o6cg.fsf@baylibre.com>
To:     Kevin Hilman <khilman@baylibre.com>
Precedence: bulk


> On 10 Feb 2022, at 5:31 am, Kevin Hilman <khilman@baylibre.com> wrote:
>=20
> Christian Hewitt <christianshewitt@gmail.com> writes:
>=20
>> 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.
>=20
> 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=E2=80=99t 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.
>=20
> 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. =20
>=20
> Kevin