fix: activate SPI DMA for STM32H7 targets

[nerdCopter]

AI Generated [pull-request]

Summary

Closes #1353.

spiInitBusDMA() (src/main/drivers/bus_spi.c) already guards
#if (defined(STM32F4) || defined(STM32F7) || defined(STM32H7)) && defined(USE_SPI) — H7
support exists in the function itself. PR #1348 only defined USE_SPI_DMA_ENABLE_LATE for
STM32F4/STM32F7 in common_fc_pre.h; H7 targets never reached the fc_init.c call
site (gated #if defined(USE_SPI) && defined(USE_SPI_DMA_ENABLE_LATE)), so spiInitBusDMA()
was dead code on every H7 target.

This PR adds the same define to the STM32H7 block, mirroring the existing F4/F7 pattern.
One line, one file.

No USE_GYRO_IMUF9001 target is STM32H7-based (HELIOSPRING/STRIXF10/MODE2FLUX are all
F4/F7), so this doesn't interact with the SPI1-exclusion guard PR #1359 added.

Tier classification

Tier 2 — behavioral change (DMA path activation), per this project's production-
readiness gates.

• Gyro verified on: pending — no STM32H7 hardware access this session
• Motor test: pending

Verification done

• make clean && CCACHE_DISABLE=1 make test: 42/42 unit test binaries pass, 0 fail.
• CCACHE_DISABLE=1 make STELLARH7DEV MATEKH743 KAKUTEH7: clean compile, zero warnings.
• Link-map cross-reference on STELLARH7DEV: spiInitBusDMA is placed at a real address
  and cross-referenced from the LTRANS object — genuinely linked in under
  -Wl,-gc-sections, not just present-but-eliminated.
• CodeRabbit GitHub review: raised a finding requesting H7 hardware validation before
  default-on, then withdrew it after re-tracing bus_spi.c/bus_spi_ll.c/
  dma_stm32h7xx.c/the H7 linker scripts — confirmed H7's DTCM/cache DMA constraints are
  already handled generically, same fallback-to-polling model as the accepted F4/F7
  precedent. Full exchange: PR review thread starting at
  fix: activate SPI DMA for STM32H7 targets #1367 (comment).

Not yet done — blocking merge

Real-hardware verification on STM32H7 (STELLARH7DEV): gyro functional test, motor arming
test, and 3x flash+reboot power cycles. No H7 hardware access this session. This PR stays
DRAFT until that verification is done.

Test plan

• make test — 42/42 pass
• Compile gate — STELLARH7DEV, MATEKH743, KAKUTEH7, zero warnings
• Link-map confirms spiInitBusDMA genuinely activated on STELLARH7DEV
• CodeRabbit GitHub review — code-level finding raised then withdrawn, no open findings
• Gyro functional test on STELLARH7DEV
• Motor arming test on STELLARH7DEV
• Flash + reboot x3 on STELLARH7DEV

[coderabbitai]

📝 Walkthrough

Walkthrough

The STM32H7 target configuration now enables USE_SPI_DMA_ENABLE_LATE alongside the existing H7 feature definitions.

Changes

STM32H7 SPI DMA configuration

Layer / File(s)	Summary
Enable late SPI DMA feature src/main/target/common_fc_pre.h	STM32H7 builds now define USE_SPI_DMA_ENABLE_LATE.

Estimated code review effort: 1 (Trivial) | ~2 minutes

Possibly related PRs

• emuflight/EmuFlight#1348: Adds the related late SPI DMA configuration for STM32F4 and STM32F7.
• emuflight/EmuFlight#1357: Relates to STM32H7 SPI DMA initialization and handlers.
• emuflight/EmuFlight#1359: Relates directly to enabling USE_SPI_DMA_ENABLE_LATE for STM32H7 builds.

Suggested labels: help wanted

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The code change satisfies issue #1353 by enabling USE_SPI_DMA_ENABLE_LATE for STM32H7 targets.
Out of Scope Changes check	✅ Passed	The pull request changes one relevant configuration line and contains no unrelated code changes.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Title check	✅ Passed	The title clearly and concisely identifies the main change: enabling SPI DMA for STM32H7 targets.
Description check	✅ Passed	The description explains the change, linked issue, verification results, and clearly identifies the remaining hardware tests and draft status.

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[nerdCopter]

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@src/main/target/common_fc_pre.h`:
- Line 100: Keep USE_SPI_DMA_ENABLE_LATE disabled by default or make it
explicitly opt-in until STELLARH7DEV validation is complete; record successful
gyro, motor, flash, and reboot hardware tests before enabling it for all USE_SPI
builds.

🪄 Autofix

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 035fff1 and 461bee6.

📒 Files selected for processing (1)

• src/main/target/common_fc_pre.h

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