OV stability fixes #334
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OV stability fixes #334
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This fix, when applied, changes the OPP voltages for the CPU from a minimum of 1V to 1.2V when creating Openvario images. This fixes freezes previously encountered even after minimum CPU voltage was increased to 1.1V. It is deliberately created as a patch to linux kernel file arch/arm/boot/dts/sun7i-a20.dtsi to always remind us to check this file when a new kernel is pulled into the OV build. Maybe at some time in the future the linux maintainers may bring this change into their code base making this patch unneccessary. It is a "follow up" change to commit #0426cb7023a415d2c4645d19ec54f9462579bd5c (read the commit message there if you want to fully understand the reasoning behind increasing minimum CPU voltage for the cubieboard) Beware this fix may not completely fix instabilities of OV as switching CPU speed has been identified as an additional cause of freeze at least on some systems. There is a separate commit for a fix stopping CPU frequency from being changed by the kernel.
During various tests with different settings for CPU voltage and CPU speed (see commit #0426cb7023a415d2c4645d19ec54f9462579bd5c and commit #5cd841d1c151f8701aefecb393a72c0bd7ea82b5) it transpired that OV runs most stable with CPU speed fixed (thus stopping the ability to change processor speed). In my lab OV has run for more than two weeks in a row with this change. I have implemented this as a small service run on (and on demand) by systemd. This service invokes /opt/bin/fix_cpu_freq.sh - a small bash script fixing scaling_min and scaling_max frequencies for the CPU at the same value. Currently this value is 720MHz which has proven to be more than sufficient for my OV (5.7 no sensorboard). If needed CPU speed can easily be changed in said script (see comments in the script). One could argue that with this patch, my previous voltage patches (see commit numbers above) would be obsolete. True, if people stay with the 720MHz. If - for some reason - people change their min/max frequencies again, the voltage patch comes in handy as it ensures high enough voltage for the CPU for reasonable stability.
linuxianer99
approved these changes
Oct 30, 2022
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Finally :-) |
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Thanks a lot!! |
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This PR contains two commits:
Further increase minimum CPU voltage to 1.2V further increases CPU voltage to 1.2V. This has proven to increase
stability greatly. However, it does not completely avoid OV freezes. It appears - at least on some OV systems - that changing CPU frequency occasionaly also creates freezes.
Fix CPU clock/frequency at 720MHz fixes the issue of CPU clock changes occasionally creating freezes by fixing CPU
clock at 720Mhz. See commit message, if you want to change the frequency to a different speed.
In combination these two fixes have created a rock solid OV (Stefly 5.7 LVDS) for me.