Previously esp_restart would stall the other CPU before enabling RTC_WDT.
If the other CPU was executing an s32c1i instruction, the lock signal
from CPU to the arbiter would still be held after CPU was stalled. If
the CPU running esp_restart would then try to access the same locked
memory pool, it would be stuck, because lock signal would never be
released.
With this change, esp_restart resets the other CPU before stalling it.
Ideally, we would want to reset the CPU and keep it in reset, but the
hardware doesn't have such feature for PRO_CPU (it is possible to hold
APP_CPU in reset using DPORT register). Given that ROM code will not use
s32c1i in the first few hundred cycles, doing reset and then stall seems
to be safe.
In addition to than, RTC_WDT initialization is moved to the beginning of
the function, to prevent possible lock-up if CPU stalling still has any
issue.
- RTC_CNTL_SLOWCLK_FREQ define is removed; rtc_clk_slow_freq_get_hz
function can be used instead to get an approximate RTC_SLOW_CLK
frequency
- Clock calibration is performed at startup. The value is saved and used
for timekeeping and when entering deep sleep.
- When using the 32k XTAL, startup code will wait for the oscillator to
start up. This can be possibly optimized by starting a separate task
to wait for oscillator startup, and performing clock switch in that
task.
- Fix a bug that 32k XTAL would be disabled in rtc_clk_init.
- Fix a rounding error in rtc_clk_cal, which caused systematic frequency
error.
- Fix an overflow bug which caused rtc_clk_cal to timeout early if the
slow_clk_cycles argument would exceed certain value
- Improve 32k XTAL oscillator startup time by introducing bootstrapping
code, which uses internal pullup/pulldown resistors on 32K_N/32K_P
pins to set better initial conditions for the oscillator.
