Before:
The cache won't be disabled when XIP on psram. But during flash
erasing/programming, read data will be courrupt.
When XIP in psram is enabled, the image is not mapped to the cache so
usually there will be no flash access. The only way to read from flash
is via the driver or use mmap. The driver has protection during erasing,
while th mmap region not.
Now:
Mmap APIs provide a flag to make mmap->unmap region mutually exclusive
to flash erase/programming when XIP from psram. SPI Flash write APIs
will benefit from this. When the flag is used, no concurrent access to
mapped region will happen while writing; otherwise the cache will be
disable to avoid data corruption.
Most ESP-IDF APIs calls mmap with this flag. As for users calling
mmap-like APIs directly, they can choose whether to enable this by a
flag.
Closes https://github.com/espressif/esp-idf/issues/14897
For the SoCs that support configurable MMU page size, it is possible
that the bootloader and application are built with different MMU page
size configuration. This mismatch is not supported at the moment and
application verification fails (at bootup or during OTA update).
Configuring MMU page size helps to optimize the flash space by having
smaller alignment and padding (secure) requirements. Please note that
the MMU page size is tied with the flash size configuration at the
moment (`ESPTOOLPY_FLASHSIZE_XMB`).
This MR ensures that application verification happens using the MMU page
size configured in its binary header. Thus, bootloader and application
can now have different MMU page sizes and different combinations shall
be supported.
1st bootloader won't help to initialize the MSPI & cache properly as it
usually do when loading from flash. And the ram app doesn't have valid
headers.
Since there is no enough space in 2nd bootloader, we replace the
`bootloader_init_spi_flash` in the ram_app (!pure_ram_app), with an
customized alternative of it for the ram_app.
This alternative helps to initialize the MSPI & cache properly, without
the help of 1st bootloader or image headers.
