rtc_clk_init fix

[negativekelvin]

Actually set cpu frequency

[igrr]

Thanks! This should probably be non-fast version, since _fast can't enable PLL, if needed?

[negativekelvin]

I thought _fast has fallback to full version if required? You are saying it will always fall back in this situation so just call it directly?

[igrr]

It does, but that relies on static variables which are not set at that point yet

[negativekelvin]

You mean s_cur_pll_freq will be zero so we won't be able to take shortcut anyway and if we happen to be setting a divided xtal freq we want to make sure pll is disabled? So no advantage in _fast.

[negativekelvin]

@igrr if we use _fast variant in esp_clk_init it can save ~10k cycles which at 80mhz is 130us do you think it is worthwhile?

ugly test code:

extern int s_cur_pll_freq;
uint8_t bbpll_endiv5_val = I2C_READREG_RTC(I2C_BBPLL, I2C_BBPLL_ENDIV5);
uint8_t bbpll_bbadc_dsmp_val = I2C_READREG_RTC(I2C_BBPLL, I2C_BBPLL_BBADC_DSMP);
if(bbpll_endiv5_val == BBPLL_ENDIV5_VAL_320M && bbpll_bbadc_dsmp_val == BBPLL_BBADC_DSMP_VAL_320M)
    s_cur_pll_freq = 320;
else if(bbpll_endiv5_val == BBPLL_ENDIV5_VAL_480M && bbpll_bbadc_dsmp_val == BBPLL_BBADC_DSMP_VAL_480M)
    s_cur_pll_freq = 480;
rtc_clk_cpu_freq_set_config_fast(&new_config);

save another ~1k cycles by giving the value of s_cur_pll_freq from bootloader to app

[igrr]

@negativekelvin Good point on the possible optimization. To resolve the issue faster, I'll take the current version of the fix, and then confirm about using I2C_READREG_RTC.

[igrr]

Squashed and cherry-picked as 8e2856b, thanks @negativekelvin!