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[71.197.186.152]) by smtp.gmail.com with ESMTPSA id k14sm8399557pgt.73.2022.02.09.12.46.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Feb 2022 12:46:21 -0800 (PST) From: Kevin Hilman To: Christian Hewitt , Rob Herring , Mark Rutland , Neil Armstrong , devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-amlogic@lists.infradead.org, linux-kernel@vger.kernel.org Cc: Christian Hewitt Subject: Re: [PATCH] arm64: dts: meson: remove CPU opps below 1GHz for G12B/SM1 In-Reply-To: <20220209135535.29547-1-christianshewitt@gmail.com> References: <20220209135535.29547-1-christianshewitt@gmail.com> Date: Wed, 09 Feb 2022 12:46:21 -0800 Message-ID: <7ha6ezojj6.fsf@baylibre.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Christian Hewitt 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. > > [0] https://github.com/khadas/linux/commit/20e237a4fe9f0302370e24950cb1416e038eee03 hehe, not a very helpful changelog in that khadas kernel commit :( > Signed-off-by: Christian Hewitt > --- > Numerous people have experienced this issue and I have tested with > only the low opp-points removed and numerous voltage tweaks: but it > makes no difference. With the opp points present an Odroid N2 or > Khadas VIM3 reliably drop off my network after being left idling > overnight with UART showing a CPU stall splat. With the opp points > removed I see weeks of uninterupted uptime. It's beyond my skills > to research what the cause of the stalls might be, but if anyone > ever figures it out we can always restore things. NB: This issue > is not too widely reported in forums, but that's largely because > most of the Amlogic supporting distros have been including this > change picked from my kernel patchset for some time. Very interesting. I've also noticed instability across suspend resume on VIM3/VIM3L and only got as far in debugging to noticing it was DVFS/OPP related, but didn't get much further yet. I'll give this a try to see if it helps. Thanks for finding & posting! Kevin