cpu/stm32: fix RAM_LEN for F427, F429, F437, F439 models

[gschorcht]

Contribution description

This PR fixes the RAM_LEN setting for STM32 F427, F429, F437, F439 models.

While playing with bootloader/riotboot_dfu, I realized that the bootloader hard faults on a stm32f429i-disc1 board here

RIOT/sys/riotboot/usb_dfu.c

Line 38 in 2d4c5a4

if (forced == 1 || *reset_addr == RIOTBOOT_MAGIC_NUMBER) {

because the RIOTBOOT_MAGIC_ADDR (which is RAM_BASE + RAM_LEN - 4) is not accessible. Although these models have 256 kByte RAM, the upper 64 kByte are used as CCM data RAM accessible at 0x1000 xxxx. Accessing 0x2003 xxxx leads to the hard fault.

Testing procedure

Use any stm32f429i-disc1 board and flash the bootloader/riotboot_dfu app:

BOARD=stm32f429i-disc1 make -C bootloaders/riotboot_dfu flash

Without this PR, the board is not listed with lsusb and dfu-util --list because it crashes in function riotboot_usb_dfu_init before the USB interface is initialized. With this PR lsusb as well as dfu-util --list should work.

Issues/PRs references

[benpicco]

Ah good catch!
Those random crashes had me puzzled for a bit.

[riot-ci]

Murdock results

✔️ PASSED

7b99a51 cpu/stm32: fix RAM_LEN for F427, F429, F437, F439 models

Success	Failures	Total	Runtime
117848	0	117848	01h:35m:17s

Artifacts

• Documentation preview

[gschorcht]

Thanks