13022591351 opened a new pull request, #19462:
URL: https://github.com/apache/nuttx/pull/19462
## Summary
The STM32H7 SDMMC driver never programs the WIDBUS bits for MMC cards:
stm32_widebus() only records the requested state and the MMC transfer
clock preset STM32_SDMMC_CLKCR_MMCXFR is hardwired to WIDBUS_D1. When the
mmcsd layer switches an eMMC device to 4-bit mode via CMD6 (MMC_SWITCH),
the host stays in 1-bit mode and all subsequent data transfers fail with
a bus width mismatch.
Program the WIDBUS bits in stm32_widebus() so the host bus width follows
the card, and add a CLOCK_MMC_TRANSFER_4BIT clock preset.
## Impact
- arch/arm/src/stm32h7: eMMC devices now actually operate in 4-bit mode;
SD card behavior is unchanged.
- include/nuttx/sdio.h: CLOCK_MMC_TRANSFER_4BIT appended to enum
sdio_clock_e (existing values are not renumbered).
- stm32f7/stm32l4 share the same stm32_widebus() pattern and may need the
same change; left for follow-up PRs as I can only test H7 hardware.
## Testing
Custom STM32H743 board with eMMC (PX4 V6X derived design), same change
verified via a backport to the PX4 NuttX 10.3 branch:
sd_bench sequential write ~4.0 MB/s, sequential read ~6.3 MB/s.
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