Entering a bootloader (ST system bootloader, or custom mboot) from software
by directly branching to it is not reliable, and the reliability of it
working can depend on the peripherals that were enabled by the application
code. It's also not possible to branch to a bootloader if the WDT is
enabled (unless the bootloader has specific provisions to feed the WDT).
This patch changes the way a bootloader is entered from software by first
doing a complete system reset, then branching to the desired bootloader
early on in the start-up process. The top two words of RAM (of the stack)
are reserved to store flags indicating that the bootloader should be
entered after a reset.
Previously the end of the heap was the start (lowest address) of the stack.
With the changes in this commit these addresses are now independent,
allowing a board to place the heap and stack in separate locations.
Recent gcc versions (at least 9.1) give a warning about using "sp" in the
clobber list. Such code is removed by this patch. A dedicated function is
instead used to set SP and branch to the bootloader so the code has full
control over what happens.
Fixes issue #4785.
If a custom bootloader is enabled (eg mboot) then machine.bootloader() will
now enter that loader. To get the original ST DFU loader pass any argument
to the function, like machine.bootloader(1).
Power and clock control is low-level functionality and it makes sense to
have it in a dedicated file, at least so it can be reused by other parts of
the code.
On F7s PLLSAI is used as a 48MHz clock source if the main PLL cannot
provide such a frequency, and on L4s PLLSAI1 is always used as a clock
source for the peripherals. This commit makes sure these PLLs are
re-enabled upon waking from stop mode so the peripherals work.
See issues #4022 and #4178 (L4 specific).
MCUs that have a PLLSAI can use it to generate a 48MHz clock for USB, SDIO
and RNG peripherals. In such cases the SYSCLK is not restricted to values
that allow the system PLL to generate 48MHz, but can be any frequency.
This patch allows such configurability for F7 MCUs, allowing the SYSCLK to
be set in 2MHz increments via machine.freq(). PLLSAI will only be enabled
if needed, and consumes about 1mA extra. This fine grained control of
frequency is useful to get accurate SPI baudrates, for example.
When waking from stop mode most of the system is still in the same state as
before entering stop, so only minimal configuration is needed to bring the
system clock back online.
With this and previous patches the stm32 port can now be compiled using
object representation D (nan boxing). Note that native code and frozen mpy
files with float constants are currently not supported with this object
representation.
If no block devices are defined by a board then storage support will be
disabled. This means there is no filesystem provided by either the
internal flash or external SPI flash. But the VFS system can still be
enabled and filesystems provided on external devices like an SD card.
On this 32-bit arch there's no need to use the long version of the format
specifier. It's only there to appease the compiler which checks the type
of the args passed to printf. Removing the "l" saves a bit of code space.
To use HSE bypass mode the board should define:
#define MICROPY_HW_CLK_USE_BYPASS (1)
If this is not defined, or is defined to 0, then HSE oscillator mode is
used.
The CMSIS files for the STM32 range provide macros to distinguish between
the different MCU series: STM32F4, STM32F7, STM32H7, STM32L4, etc. Prefer
to use these instead of custom ones.
This patch allows to completely compile-out support for USB, and no-USB is
now the default. If a board wants to enable USB it should define:
#define MICROPY_HW_ENABLE_USB (1)
And then one or more of the following to select the USB PHY:
#define MICROPY_HW_USB_FS (1)
#define MICROPY_HW_USB_HS (1)
#define MICROPY_HW_USB_HS_IN_FS (1)
Newer versions of the HAL use names which are cleaner and more
self-consistent amongst the HAL itself. This patch switches to use those
names in most places so it is easier to update the HAL in the future.
The calls to rtc_init_start(), sdcard_init() and storage_init() are all
guarded by a check for first_soft_reset, so it's simpler to just put them
all before the soft-reset loop, without the check.
The call to machine_init() can also go before the soft-reset loop because
it is only needed to check the reset cause which can happen once at the
first boot. To allow this to work, the reset cause must be set to SOFT
upon a soft-reset, which is the role of the new function machine_deinit().
This is to keep the top-level directory clean, to make it clear what is
core and what is a port, and to allow the repository to grow with new ports
in a sustainable way.
