Fix SD card busy-wait loops that can lock up flight controller

[sensei-hacker]

User description

Summary

• Add timeout guards to unbounded busy-wait loops in the SD card SPI and SDIO drivers
• A problematic SD card could cause sdcardSpi_deselect() to spin forever on busIsBusy(), freezing the entire FC since blackbox runs inline with the PID loop via processBlackbox() in fc_core.c
• This is a safety-critical fix: peripheral failures must never take down the flight controller

Changes

sdcard_spi.c — sdcardSpi_deselect() (called ~15 times after every SPI transaction):

• Replace unbounded while (busIsBusy) { __NOP(); } with 100K-iteration timeout (~4µs at 168MHz)
• On timeout: increment failureCount, disable card at threshold (8), always release SPI CS line
• Matches the existing timeout pattern in sdcardSpi_init() (line 864)
• Transient recovery: failureCount resets to 0 on any successful read/write

sdmmc_sdio_f4xx.c — DMA disable loop:

• Add 10K-iteration timeout to while (pDMA->CR & DMA_SxCR_EN) (~0.4µs)
• DMA disable normally completes in a few bus cycles; subsequent SDIO hardware timeout catches failures

sdmmc_sdio_f4xx.c — FIFO read loops (3 locations: SD_HighSpeed, SD_GetCardStatus, SD_FindSCR):

• Add SD_DATATIMEOUT software iteration counter as defense-in-depth behind hardware SDIO_STA_DTIMEOUT
• These are init-only code paths (not in PID loop), so the large counter is acceptable

Test plan

• Build for MATEKF405 (F4/SDIO target) — clean
• Build for OMNIBUSF4V3 (F4/SPI-SD target) — clean
• Hardware test with known-good SD card (regression)
• Hardware test with problematic/removed SD card (timeout recovery)

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PR Type

Bug fix

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Description

• Add timeout guards to unbounded busy-wait loops in SD card drivers

  • sdcard_spi.c: 100K-iteration timeout in sdcardSpi_deselect() with failure tracking
  • sdmmc_sdio_f4xx.c: 10K-iteration timeout for DMA disable loop
  • sdmmc_sdio_f4xx.c: Software timeout backstops in three FIFO read loops

• Prevents flight controller lockup from problematic SD cards during blackbox operations

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Diagram Walkthrough

flowchart LR
  A["Problematic SD Card"] -->|triggers unbounded loop| B["busIsBusy/DMA/FIFO loops"]
  B -->|without timeout| C["Flight Controller Lockup"]
  B -->|with timeout| D["Graceful Failure Handling"]
  D -->|increment failureCount| E["Disable Card at Threshold"]
  D -->|release resources| F["Continue Operation"]

Loading

File Walkthrough

Relevant files

Bug fix

sdcard_spi.c Add timeout to SPI deselect busy-wait loop                              src/main/drivers/sdcard/sdcard_spi.c Replace unbounded while (busIsBusy) loop with 100K-iteration timeout (~4µs at 168MHz) Increment failureCount on timeout and disable card when threshold (8) is reached Always release SPI CS line via busDeselectDevice() after timeout Matches existing timeout pattern from sdcardSpi_init() +11/-1    sdmmc_sdio_f4xx.c Add timeouts to DMA and FIFO read loops                                    src/main/drivers/sdcard/sdmmc_sdio_f4xx.c Add 10K-iteration timeout to DMA disable loop in SD_StartBlockTransfert() (~0.4µs) Add SD_DATATIMEOUT software iteration counter to three FIFO read loops: SD_HighSpeed(), SD_GetCardStatus(), and SD_FindSCR() Software timeouts provide defense-in-depth behind hardware SDIO_STA_DTIMEOUT Init-only code paths allow larger timeout counters without PID loop impact +14/-1

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[qodo-code-review]

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