I am looking for ways to reduce the Colibri VF50 energy consumption under Linux/Yocto. I saw that Suspend to RAM is supported (Suspend/Resume (Linux)). Is the requirement of disabled Ethernet PHY up to date?
Other points:
What about other low-power states (LPStop, LPRun and ULPRun). Are these supported by Linux BSP? I could not find respective cpuidle driver for them.
Is CPU frequency and voltage scaling supported? E.g. with cpufreq-dt driver?
LPStop is supported through Linux suspend mechanism. See also our Suspend/Resume (Linux) article.
No CPU frequency/voltage scaling is supported. In general the hardware architecture is not really designed to do DVFS. Voltage scaling is definitly not supported. Frequency scaling might be possible to some degree (e.g. lowering from 500 to 400MHz), but it power savings are probably minimal. Setting even lower frequencies, and really saving power (like the LPRun would allow) has some major side effects on all peripherals (e.g. UART clocks etc…). Linux does not have good infrastructure which makes such system wide clock changing possible…
In general, the Vybrid is not really a low power module due to its rather large SRAM (which by its nature burns a lot of power) and older process technology. The Colibri iMX7 typically use less power than Vybrid while providing more CPU performance.
