In #12955 optimization was switched to O2 because with the '-Os'
option, the ESP32 hangs sporadically in 'tests/bench*' if
interrupts where disabled too early by benchmark tests.
Since it hasn't been reproduced since and in #13196 O2 was causing
un-explained hardfaults, since the aforementioned issue could not
be reproduced we switch back to Os by removing O2, as Os will be
used by default.
When entering a sleep mode, all wake-up sources should first be disabled before the wake-up sources required for the sleep mode are then stepwise enabled again. Otherwise, an wake-up configuration of one sleep mode may affect the wake-up within another sleep mode.
The WiFi interface should be stopped before reboot or sleep. But stopping the WiFi interface disconnects an existing connection. Usually, esp_wifi_netdev tries to reconnect on an disconnect event. However, trying reconnect with a stopped WiFi interface may lead to a crash. Therefore, the stop event has to be handled.
Now, where the vendor files for light/deep sleep mode are added, function `pm_off` does not need to implement this mode by itself. Instead the existing deep sleep with disabled wakeup sources is used for pm_off.
`rtc_init` is used after light sleep to update the system time from RTC timer. The fix corrects a small difference of about 230 ms which would sum up with each wakeup from light sleep.
By using a custom EPOCH for the RTC implementation, we can extend the
range of the 32 bit counter based RTC by 118 years.
It also reduces the code size compared to the stdlib based POSIX functions.
To be able to define common configurations for all ESP CPUs, the CPU specific configuration cpu_conf.h has to include a common configuration. For that purpose cpu_conf.h in cpu/esp_common is renamed to cpu_conf_common.h and included in CPU specific configurations.
During the write access to the SPI flash, the IROM cache is not available and only code from the IRAM can be executed. Therefore, the code of file system implementations which access the SPI flash must reside in IRAM.
