Add option to use CCMRAM on F303xE.

[JammuKekkonen]

Description (required)

Add option to place data to ccm ram on STM32F303xE. Similar functionality exists already for at least STM32F437xG target.

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Pull request type (required)

[X] Patch update (Bug fix / Target update / Docs update / Test update / Refactor)
[] Feature update (New feature / Functionality change / New API)
[] Major update (Breaking change E.g. Return code change / API behaviour change)

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Test results (required)

[] No Tests required for this change (E.g docs only update)
[] Covered by existing mbed-os tests (Greentea or Unittest)
[] Tests / results supplied as part of this PR

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Reviewers (optional)

@anttiylitokola @teetak01

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Release Notes (required for feature/major PRs)

Summary of changes

Impact of changes

Migration actions required

[ciarmcom]

@JammuKekkonen, thank you for your changes.
@anttiylitokola @teetak01 @ARMmbed/mbed-os-maintainers please review.

[0xc0170]

CI started

[JanneKiiskila]

@ARMmbed/team-st-mcd for your review, too.

[JanneKiiskila]

@0xc0170 @adbridge - preferrably to next Mbed OS patch release, please.

[mbed-ci]

Test run: SUCCESS

Summary: 11 of 11 test jobs passed
Build number : 1
Build artifacts

[kjbracey-arm]

Could you reorder this? It's confusing because you've put the CCM RAM in between RW_IRAM1 and ARM_LIB_STACK, which are adjacent.

It's probably a good idea to name the execution region CCMRAM too, if you're manually directing stuff there. RW_IRAM2 could be construed as general-purpose RAM.

(I'm assuming you're not viewing it as general-purpose RAM, or you would be directing general stuff there. Comment should probably say that rather than "RW data").

[JammuKekkonen]

Current way follows the naming and location in F437xG.

[kjbracey-arm]

Feel free to fix that too.

[kjbracey-arm]

Ooh, 437's sct is a mess. It's got 5 RAM regions, three of which are adjacent, but they're all separated in the map.

The three together are (RW_m_crash_data, RW_IRAM1, ARM_LIB_STACK) in that order, then RW_IRAM2 (CCMRAM) and RW_IRAM3 (BKPSRAM) are separate.

Its GCC ld and IAR icf seem neat enough.

[JammuKekkonen]

fixed the order and renamed to CCMRAM

[kjbracey-arm]

General thought, which you don't need to address here. Any platform which does have CCM RAM probably should use it for at least the boot/interrupt stack, and maybe the main thread stack.

Those are a lot of your scratch space which you'd want to be fast, and you probably get away with avoiding any bus mastering issues that stop you viewing it as general-purpose static/heap RAM - you won't be generally trying to DMA into the stack.

And gives you a RAM saving without any explicit application area attribute additions.

[0xc0170]

@ARMmbed/team-st-mcd ^^ review the suggestion above

[kjbracey-arm]

Discussed with @JammuKekkonen - this is fine as-is, but the F303 doesn't have Ethernet, and there's no DMA in the HAL, so we can see no reason not to treat the CCMRAM as general-purpose RAM for Mbed OS. So a later extension might be to pop a .ANY(+RW,+ZI) in there as well as this .ANY(CCMRAM) that gives you manual direction. And maybe the ARM_LIB_STACK.

The F437 does have Ethernet, but some boards don't. Maybe the F437 scatter file could do the same based on a #if !DEVICE_EMAC.

[0xc0170]

CI started

Still waiting for @ARMmbed/team-st-mcd review

[mbed-ci]

Test run: SUCCESS

Summary: 11 of 11 test jobs passed
Build number : 2
Build artifacts

[jeromecoutant]

ST CI OK with NUCLEO_F303ZE and NUCLEO_F303RE