STM32F7 Flash Dual Bank support

[dhwalters423]

Description

In order to support sensible SOTP and NV Store values, the STM32F7 platforms should have dual bank flash support.

At the moment this is not supported:

mbed-os/targets/TARGET_STM/TARGET_STM32F7/flash_api.c

Line 109 in 79640c6

/* We don't support the DUAL BANK MODE for now, so return error */

Impact:
In order to support drag and drop programming of devices with Mbed Cloud Client, we need to set the SOTP regions to the end of the bank. This allows consistent device identity and the ability to use the RoT in the SOTP sector.

Example:
The NUCLEO_F746ZG platform has 1Mb of flash. The flash sectors at the end of the single bank are 256kb a piece (at 0x08080000 and 0x080C0000). Therefore SOTP is taking up more than half the available flash on the board. By enabling dual bank flash sectors, the end sectors would only be 128kb, thus taking up 25% rather than 50% of the available flash memory.

Issue request type

[ ] Question
[X ] Enhancement
[ ] Bug

[0xc0170]

@ARMmbed/team-st-mcd Please review

[jeromecoutant]

Hi
For information, STM32F746ZG doesn't support dual bank.
Dual bank feature seems to be supported only for STMF76x MCU

[dhwalters423]

Thanks for clarification @jeromecoutant
This is still important for those platforms with dual bank support- NUCLEO_F767ZI for example.

[0xc0170]

Dual bank feature seems to be supported only for STMF76x MCU

@jeromecoutant What would take to enable that ? Are there any limitations to be aware of , drawbacks or?

[bcostm]

Can you please verify if this PR solves your issue ? and close it if ok. Thanks

[ciarmcom]

ARM Internal Ref: MBOTRIAGE-23

[dannybenor]

@dhwalters423 Can you please review?

[bcostm]

@0xc0170 can you please add the device: st label ?

[dhwalters423]

#7088 reviewed and tested, thank you @bcostm