1. add hal and low-level layer for timer group
2. add callback functions to handle interrupt
3. add timer deinit function
4. add timer spinlock take function
There used to be dummy phase before out phase in common command
transactions. This corrupts the data.
The code before never actually operate (clear) the QE bit, once it finds
the QE bit is set. It's hard to check whether the QE set/disable
functions work well.
This commit:
1. Cancel the dummy phase
2. Set and clear the QE bit according to chip settings, allowing tests
for QE bits. However for some chips (Winbond for example), it's not
forced to clear the QE bit if not able to.
3. Also refactor to allow chip_generic and other chips to share the same
code to read and write qe bit; let common command and read command share
configure_host_io_mode.
4. Rename read mode to io mode since maybe we will write data with quad
mode one day.
1. simplify deallocate in esp_eth_mac_new_esp32, esp_eth_mac_new_dm9051
2. remove blocking operation in os timer callback
3. check buffer size in ethernet receive function
This commit refactors backtracing within the panic handler so that a common
function esp_backtrace_get_next_frame() is used iteratively to traverse a
callstack.
A esp_backtrace_print() function has also be added that allows the printing
of a backtrace at runtime. The esp_backtrace_print() function allows unity to
print the backtrace of failed test cases and jump back to the main test menu
without the need reset the chip. esp_backtrace_print() can also be used as a
debugging function by users.
- esp_stack_ptr_is_sane() moved to soc_memory_layout.h
- removed uncessary includes of "esp_debug_helpers.h"
Using xxx_periph.h in whole IDF instead of xxx_reg.h, xxx_struct.h, xxx_channel.h ... .
Cleaned up header files from unnecessary headers (releated to soc/... headers).
This MR removes the common dependency from every IDF components to the SOC component.
Currently, in the ``idf_functions.cmake`` script, we include the header path of SOC component by default for all components.
But for better code organization (or maybe also benifits to the compiling speed), we may remove the dependency to SOC components for most components except the driver and kernel related components.
In CMAKE, we have two kinds of header visibilities (set by include path visibility):
(Assume component A --(depends on)--> B, B is the current component)
1. public (``COMPONENT_ADD_INCLUDEDIRS``): means this path is visible to other depending components (A) (visible to A and B)
2. private (``COMPONENT_PRIV_INCLUDEDIRS``): means this path is only visible to source files inside the component (visible to B only)
and we have two kinds of depending ways:
(Assume component A --(depends on)--> B --(depends on)--> C, B is the current component)
1. public (```COMPONENT_REQUIRES```): means B can access to public include path of C. All other components rely on you (A) will also be available for the public headers. (visible to A, B)
2. private (``COMPONENT_PRIV_REQUIRES``): means B can access to public include path of C, but don't propagate this relation to other components (A). (visible to B)
1. remove the common requirement in ``idf_functions.cmake``, this makes the SOC components invisible to all other components by default.
2. if a component (for example, DRIVER) really needs the dependency to SOC, add a private dependency to SOC for it.
3. some other components that don't really depends on the SOC may still meet some errors saying "can't find header soc/...", this is because it's depended component (DRIVER) incorrectly include the header of SOC in its public headers. Moving all this kind of #include into source files, or private headers
4. Fix the include requirements for some file which miss sufficient #include directives. (Previously they include some headers by the long long long header include link)
This is a breaking change. Previous code may depends on the long include chain.
You may need to include the following headers for some files after this commit:
- soc/soc.h
- soc/soc_memory_layout.h
- driver/gpio.h
- esp_sleep.h
The major broken include chain includes:
1. esp_system.h no longer includes esp_sleep.h. The latter includes driver/gpio.h and driver/touch_pad.h.
2. ets_sys.h no longer includes soc/soc.h
3. freertos/portmacro.h no longer includes soc/soc_memory_layout.h
some peripheral headers no longer includes their hw related headers, e.g. rom/gpio.h no longer includes soc/gpio_pins.h and soc/gpio_reg.h
BREAKING CHANGE
1. separate rom include files and linkscript to esp_rom
2. modefiy "include rom/xxx.h" to "include esp32/rom/xxx.h"
3. Forward compatible
4. update mqtt
The following 2 compiler warnings are only reproducible when setting:
OPTIMIZATION_FLAGS = -Ofast
esp-idf/components/soc/esp32/rtc_clk.c:
In function 'rtc_clk_cpu_freq_get':
esp-idf/components/soc/esp32/rtc_clk.c:506:12:
error: 'freq' may be used uninitialized in this function
[-Werror=maybe-uninitialized]
return freq;
esp-idf/components/esp_ringbuf/ringbuf.c:
In function 'xRingbufferReceiveSplitFromISR':
esp-idf/components/esp_ringbuf/ringbuf.c:934:26:
error: 'pvTempTailItem' may be used uninitialized in this function
[-Werror=maybe-uninitialized]
*ppvTailItem = pvTempTailItem;
Closes https://github.com/espressif/esp-idf/pull/2878
1. fix error when fading is too fast
2. fix error when setting duty and update immediately
3. update register header file to be in accord with TRM
closes https://github.com/espressif/esp-idf/issues/2903
A workaround to reset BBPLL configuration after light sleep. Fixes the
issue that Wi-Fi can not receive packets after waking up from light
sleep.
Ref. https://github.com/espressif/esp-idf/issues/2711
If zero-overhead loop buffer is enabled, under certain rare conditions
when executing a zero-overhead loop, the CPU may attempt to execute an invalid instruction. Work around by disabling the buffer.
This commit resolves a blocking in esp_aes_block function.
Introduce:
The problem was in the fact that AES is switched off at the moment when he should give out the processed data. But because of the disabled, the operation can not be completed successfully, there is an infinite hang. The reason for this behavior is that the registers for controlling the inclusion of AES, SHA, MPI have shared registers and they were not protected from sharing.
Fix some related issue with shared using of AES SHA RSA accelerators.
Closes: https://github.com/espressif/esp-idf/issues/2295#issuecomment-432898137
Introduced in 97e3542947.
The previous commit frees the IRAM part when single core, but doesn't
change the memory layout functions. The unit test mallocs IRAM memory
from the heap, accidently into the new-released region, which doesn't
match the memory layout function.
This commit update the memory layout function to fix this.
Some logging done in soc component may happen before logging via
stdout is possible. Use _EARLY version of log calls to make sure that
output is visible. The downside is that application does not have a
way to silence these logs. However since the soc component doesn’t
use any LOGV/LOGD/LOGI and only logs warnings and errors, this should
not impact the application.
When CONFIG_ESP32_RTCDATA_IN_FAST_MEM is enabled, RTC data is placed
into RTC_FAST memory region, viewed from the data bus. However the
bootloader was missing a check that this region should not be
overwritten after deep sleep, which caused .rtc.bss segment to loose
its contents after wakeup.
Works for 3.3V eMMC in 4 line mode.
Not implemented:
- DDR mode for SD cards (UHS-I) also need voltage to be switched to 1.8V.
- 8-line DDR mode for eMMC to be implemented later.
Previous APIs used to set CPU frequency used CPU frequencies listed in
rtc_cpu_freq_t enumeration. This was problematic for two reasons.
First, supporting many possible frequency values obtained by dividing
XTAL frequency was hard, as every value would have to be listed in
the enumeration. Since different base XTAL frequencies are supported,
this further complicated things, since not all of these divided
frequencies would be valid for any given XTAL frequency. Second,
having to deal with enumeration values often involved switch
statements to convert between enumeration and MHz values, handle
PLL/XTAL frequencies separately, etc.
This change introduces rtc_cpu_freq_config_t structure, which contains
CPU frequency (in MHz) and information on how this frequency has to
be generated: clock source (XTAL/PLL), source frequency, clock
divider value. More fields can be added to this structure in the
future. This structure simplifies many parts of the code, since both
frequency value and frequency generation settings can be accessed in
any place in code without the need for conversions.
Additionally, this change adds setting of REF_TICK dividers to support
frequencies lower then XTAL with DFS.
For pins 32 and up the BIT(nr) macro used here overflowed,
causing undetermined GPIO pins to be reset.
Example: freeing SPI device/bus where CS is on pin 33
caused debug UART to cease communication, TXD0 was
disabled.
Fixed as BIT64(nr) macro, to be used elsewhere as needed.
For example in definitions like GPIO_SEL_32..GPIO_SEL_39.
No longer necessary to keep all reserved addresses in 'soc'.
Means 'soc' does not need to know about 'bt', for example.
Also means that Bluetooth can be enabled in config without any memory being reserved for BT
controller. Only if code calling the BT controller is linked in, will this memory be reserved...
Fixed the error division on zero.
Also fixed range CONFIG_ESP32_RTC_CLK_CAL_CYCLES in Kconfig.
Fixed a overflow error by TIMG in the function rtc_clk_cal_internal. This error was due to a limit in values TIMG_RTC_CALI_MAX=0x7FFF (to write the slowclk_cycles) and TIMG_RTC_CALI_VALUE=0x1FFFFFF (to read xtal_cycles). Added assert finctions.
Closes https://github.com/espressif/esp-idf/issues/2147
A new method of workaround an error with DPORT is to ensure that the APB is read and followed by the DPORT register without interruptions and pauses. This fix places this implementation in the IRAM to exclude errors associated with the cache miss.
1. provide options for bluetooth low power mode
2. provide two options for bluetooth low power clock: main XTAL and external 32kHz XTAL
3. provide function and callbacks to control bluetooth low power mode, including enable/disable sleep, software wakeup request, low power clock settings, check power state, etc
4. modify vhci API vhci_host_send_packet to use blocking mode
5. note that DFS and bluetooth modem sleep can not be used together currently.
If the RTC crystal is bad or has no matched capacitance, then you do not need to start such the crystal. It is necessary to determine this case, output an error (about impossibility to start from the oscillator) and start from the internal RC of the chain.
Reduced the default value of the number of bootstrap cycles. Because we can oscillating the oscillator which then stops. (in Kconfig). Changed from 100 to 5.
The number of calibration cycles has been increased. It is the main criterion for estimating the launch of an oscillator. A large increase leads to an increase in the load time, as well as the stability of recognition of this case. (in Kconfig).
Changed from 1024 to 3000.
When two CPUs read the area of the DPORT and the area of the APB, the result is corrupted for the CPU that read the APB area.
And another CPU has valid data.
The method of eliminating this error.
Before reading the registers of the DPORT, make a preliminary reading of the APB register.
In this case, the joint access of the two CPUs to the registers of the APB and the DPORT is successful.
Previous version of the code only connected CD and WP to the
peripheral, in fact the hardware does not use the values of these
signals automatically. This adds code to read CD and WP values when
command is executed and return errors if card is not present, or
write command is executed when WP signal is active.
- Add SDIO support at protocol layer (probing, data transfer, interrupts)
- Add SDIO interrupts support in SDMMC host
- Add test (communicate with ESP32 in SDIO download mode)
Previous code contained a check for PLL frequency to be 240MHz, while
in fact 240MHz was a CPU frequency; corresponding PLL frequency is
480MHz. Fixed the comparison and replaced integer MHz values with an
enum.
1. External 32kHz crystal is started for too long or it may not start at all. It is often observed at the first start.
2. At the first start, it is possible that the crystal did not start. And the recorded period was recorded as 0. Which led to a division error by zero during the transition to the deep sleep mode (Maybe somewhere else).
3. Added a unit test to test a new method of oscillation an external crystal.
4. Added a new method of oscillating of an external crystal. The legs of the crystal are fed with a 32 kHz frequency.
The new method eliminates these errors.
Added unit test: `\esp-idf\components\soc\esp32\test\test_rtc_clk.c`: `make TEST_COMPONENTS=soc`
- 8 Test starting external RTC crystal. Will pass.
`Bootstrap cycles for external 32kHz crystal` - is specified in the file Kconfig by default 100.
QA tested a new method of oscillation the crystal on 25 boards. The supply of square waves on the crystal showed a 100% result in contrast to the previous method of launching the crystal. After the tests, the old method was deleted.
Closes TW19143
The fast path of CPU frequency switch function, used in DFS, was not
waiting for the frequency switch to complete when switching from XTAL
to PLL. This resulted in incorrect reads from peripherals on APB,
where two consecutive reads could return the same value. For example,
in esp_timer, read of FRC_COUNT_REG would return same value as the
preceding read of FRC_ALARM_REG, causing time to jump by the value of
FRC_ALARM_REG / apb_freq_mhz.
This commit adds support for CPU max freqeuency rating
bits in CPU. Bootloader will now print an error if attempting
to 160MHz rated ESP32 at 240MHz.
EFUSE_CHIP_VER_RESERVE has been replaced by the
frequency rating bits. Dependancies on EFUSE_CHIP_VER_RESERVE
have been changed to use EFUSE_CHIP_VER_PKG
This commit removes the lookup table mode due to inferior performance when compared
to linear mode under attenuation 0, 1 and 2. However small portions of the lookup table
are kept for the higher voltages of atten 3 (above ADC reading 2880). That voltage range
in atten 3 has non linear characteristics making the LUT performan better than linear mode.
This commit updates the esp_adc_cal ocmponent to support new calibration methods
which utilize calibratoin values stored in eFuse. This commit includes LUT mode
The TRM describes IOMUX registers are IO_MUX_x_REG for x in GPIO0-39.
Until now ESP-IDF describes them as PERIPHS_IO_MUX_(pinname)_U
This commit adds additional IOMUX register names which match the ones used in the TRM.
RTC_FAST_CLK_FREQ_APPROX is defined as 8500000, so 0.5MHz part was lost
when dividing by MHZ. Since cal_val is 64-bit the parens can be removed.
With 40MHz XTAL for a nominal ESP32 chip, this fixes estimated XTAL
frequency from 38 to 40MHz.
To achieve reliable operation with GD flash at 80MHz, need to raise
core voltage.
This causes the following current consumption increase:
At 80MHz: from 29mA to 33mA
At 160MHz: from 41mA to 47mA
Test conditions: 2 cores running code from IRAM, remaining peripherals
clock gated.
1. move settings of WIFI_CLK_EN_REG for bluetooth into controller init/deinit APIs
2. modify the bit mask used in phy_rf init/deinit to use WIFI-BT shared bits
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.
1. Make sure that 8MD256 clock used to estimate XTAL frequency is enabled
before trying to use rtc_clk_cal_ratio.
This fixes "Bogus XTAL frequency: 0 MHz" warnings after software reset.
2. Don't call rtc_clk_xtal_freq_estimate if XTAL frequency is already
known. This reduces startup time after deep sleep or software reset.
3. Compare known XTAL frequency and estimated one before printing a
warning. This fixes "Possibly invalid CONFIG_ESP32_XTAL_FREQ setting
(40MHz). Detected 40 MHz." warnings.
Previous implementation waited for 20us after setting
RTC_CNTL_SOC_CLK_SEL_XTL register, using ets_delay_us, assuming that
the CPU was running at XTAL frequency. In reality, clock switch happened
on the next RTC_SLOW_CLK cycle, and CPU could be running at the previous
frequency (for example, 240 MHz) until then.
ets_delay_us would wait for 20 us * 40 cycles per us = 800 CPU cycles
(assuming 40 MHz XTAL; even less with a 26 MHz XTAL).
But if CPU was running at 240 MHz, 800 cycles would pass in just 3.3us,
while SLOW_CLK cycle could happen as much as 1/150kHz = 6.7us after
RTC_CNTL_SOC_CLK_SEL_XTL was set. So the software would not actually wait
long enough for the clock switch to happen, and would disable the PLL
while CPU was still clocked from PLL, leading to a halt.
This implementation uses rtc_clk_wait_for_slow_cycle() function to wait
until the clock switch, removing the need to wait for a fixed number of
CPU cycles.
Some RTC features are synchronized to RTC_SLOW_CLK, so sometimes
software needs to wait for the next slow clock cycle.
This function implements waiting using Timer Group clock calibration
feature.
append adc support and api
- esp_err_t adc2_config_width(adc_bits_width_t width_bit);
- esp_err_t adc2_config_channel_atten(adc2_channel_t channel, adc_atten_t atten);
- int adc2_get_voltage(adc2_channel_t channel);
Internal byte accessible memory starts with Internal ROM 1 at 0x3FF90000.
Region of RTC fast memory starting at 0x3FF80000 is not used in IDF as
it is mapped to PRO CPU only.
1. Support built-in ADC for I2S.
2. Modify code of ADC, made no change to the original APIs.
3. Add APIs in I2S:
esp_err_t i2s_set_adc_mode(adc_unit_t adc_unit, adc1_channel_t adc_channel);
4. Add I2S ADC/DAC example code.
5. add old-fashion definition to make it more compatible
6. replase spi_flash_ APIs with esp_partition_ APIs
7. add example of generating audio table from wav
8. change example sound
Since 9a8c0392, XTAL frequency is set to 40MHz by default, and users
of 26MHz boards need to select 26MHz manually. Most users are not aware
of this change, and existing getting started guides do not mention that
XTAL frequency needs to be set for some boards. So users are left with
garbage output from UART without any clue what to check.
This change adds a warning in case specific XTAL frequency was set, and
it does not match automatically detected one. This should help users
fix the issue.
All peripheral clocks are default enabled after chip is powered on.
When CPU starts, if reset reason is CPU reset, disable those clocks
that are not enabled before reset. Otherwise, disable all those
useless clocks.
These peripheral clocks must be enabled when the peripherals are
initialized and disabled when they are deinitialized.
1. BIT(8) of CTRL is actually read-only bit indicating interrupt status
2. BIT(0) or CTRL had inverted meaning: 1 is “level”, 0 is “edge”
3. Add definitions of prescaler values
1. add sens_struct.h
2. add definition of RTCCNTL and RTCIO
3. modify touch pad examples
4. update example code.
5. add comments add option in menuconfig
6. fix issue that pad index 8 and 9 are mismatched
7. add touch_pad_read_filtered() api to get value filtered by iir filter
8. modify touch pad isr func
9. Make the items in perihperal.ld in the sequence of address
10. delete Kconfig for touch pad
11. add touchpad filter APIs to adjust the filter
12. add touch_pad into index.rst
13. add touch_pad in Doxyfile
14. add touch_pad.rst
The address field should be placed at the highest bits of address and slv_wr_status registers. Instead of breaking the address into two parts and fill in each register, move the address to the highest bits and write to the registers respectively.
Breaking change: if you fill-in the SPI address filed in a previous version in some way and it works correctly, you still have to rewrite the address, in a more intuitive way.
Makes app image booting more reliable (256-bit rather than 8-bit verification.)
Some measurements, time to boot a 655KB app.bin file and run to app_main() execution.
(All for rev 1 silicon, ie no 340ms spurious WDT delay.)
80MHz QIO mode:
before = 300ms
after = 140ms
40MHz DIO mode:
before = 712ms
after = 577ms
40MHz DIO mode, secure boot enabled
before = 1380ms
after = 934ms
(Secure boot involves two ECC signature verifications (partition table, app) that take approx 300ms each with 80MHz CPU.)
Because of errata related to BOD reset function, brownout is handled as follows:
- attach an ISR to brownout interrupt
- when ISR happens, print a message and do a software restart
- esp_restart_nonos enables RTC watchdog, so if restart fails,
there will be one more attempt to restart (using the RTC
watchdog)
RTC watchdog didn’t have any actions configured for any of the stages.
This change configures it to use SW_SYSTEM_RESET at stage 0 and a
full reset at stage 1. The timeout is now calculated based on
RTC_SLOW_CLK frequency.
1. Name change from chopper to carrier, block diagram update, minor changes to example codes
2. mcpwm_reg.h changed, brought uniformity in comments, worked on suggestions, duty to accept float. Some name changes!
3. Minor readme changes and Indetation
4. Minor change: move mcpwm_reg.h and mcpwm_struct.h to new path
5. Minor change: addition of BLDC example code and Readme
6. Name changed from epwm to mcpwm
7. Improve the reg name in mcpwm_struct.h
8. Name change chopper>carrier, deadband>deadtime
add API to get chip info
This change adds an API to get chip info, such as chip model, enabled capabilities, size of embedded flash, silicon revision.
Hello_world example is modified to print out the information about the chip. The example is also simplified by moving all code into the main task.
Ref TW12031.
See merge request !549
1. When dual core cpu run access DPORT register, must do protection.
2. If access DPORT register, must use DPORT_REG_READ/DPORT_REG_WRITE and DPORT_XXX register operation macro.
Split common SPI stuff out of master driver; add slave driver; add workaround for DMA issue.
This merge req mainly adds a slave device. In order to do this, the original master driver is refactored into common code shared by master and slave modes, and a slave driver is added.
The other things added are:
- Added a workaround for a 'feature' of the ESP32 silicon that can lock up the receive DMA channel in some situations. This can only be fixed by resetting *both* DMA channels. The workaround implemented makes sure that the reset only happens when both channels are idle
- Got rid of the automatic choice between register- and DMA-based transfers. The master (and slave) code will now always go for a DMA transfer if a DMA channel is given, and always go for register-based transfers if no DMA channel is given.
- Add in a bunch of fixes for outstanding Github issues.
See merge request !659
add support for 32k XTAL as RTC_SLOW_CLK source
- 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.
Ref TW11683.
Ref https://esp32.com/viewtopic.php?f=13&t=1570
Fixes https://github.com/espressif/esp-idf/issues/337.
See merge request !696
- 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.
ROM code already implements XTAL frequency detection, but it uses the 8M
clock before the clock tuning parameters are initialized. With the
zero clock tuning parameter, 8M clock has significant frequency deviation
at high temperatures, which can lead to erroneous detection of 40 MHz
crystal as a 26 MHz one.
This change adds XTAL frequency detection code to rtc_clk_init routine,
and detection is performed after the 8M clock tuning parameter as been
initialized.
soc: allow REG_SET_FIELD to be used for bit fields
- Fixes an issue with `rtc_clk_apll_enable`: https://esp32.com/viewtopic.php?f=13&t=1673
- Fixes `rtc_clk_fast_freq_set` function always selecting XTAL/4 as fast clock source.
- Fixes regression in deep sleep current (7uA instead of 5uA).
See merge request !674
On first reset, ROM code writes the estimated XTAL frequency into
RTC_APB_FREQ_REG (aka STORE5). If the application doesn’t specify exact
XTAL frequency (which is always the case for now), rtc_clk_init will
guess what kind of XTAL is used (26M or 40M), based on the estimated
frequency. Later, detected frequency is written into RTC_XTAL_FREQ_REG
(aka STORE4).
When the application switches clock source to PLL, APB frequency changes
and RTC_APB_FREQ_REG is updated. If the application encounters an RTC
WDT reset, RTC_APB_FREQ_REG will not be updated prior to reset. Once the
application starts up again, it will attempt to auto-detect XTAL
frequency based on RTC_APB_FREQ_REG, which now has value of 80000000.
This will fail, and rtc_clk_xtal_freq_estimate will fall back to the
default value of 26 MHz. Due to an incorrect XTAL frequency, PLL
initialization will also take incorrect path, and PLL will run at a
different frequency. Depending on the application this may cause just
garbage output on UART or a crash (if WiFi is used).
