pub fn max_cpu_frequency() -> Rate {
        let has_rating = Self::read_bit(CHIP_CPU_FREQ_RATED);
        let has_low_rating = Self::read_bit(CHIP_CPU_FREQ_LOW);

        if has_rating && has_low_rating {
            Rate::from_mhz(160)
        } else {
            Rate::from_mhz(240)
        }
    }
Returns the maximum rated clock of the CPU in MHz.

Note that the actual clock may be lower, depending on the current power
configuration of the chip, clock source, and other settings.
esp-hal/src/soc/esp32/efuse/mod.rs