jasonbu opened a new pull request, #18501:
URL: https://github.com/apache/nuttx/pull/18501
## Summary
Add GPIO and eMMC (USDHC) support for the i.MX95 A55 EVK board, enabling
8-bit eMMC access with MBR/GPT partition table parsing.
## Changes
### 1. `imx9: add GPIO support for imx95`
- Add imx95 GPIO register definitions (same IP block as imx93)
- Fill `g_gpio_base[]` array for imx95
- Include `imx95_gpio.h` from the common header
- Compile `imx9_gpio.c` / `imx9_gpiobase.c` for imx95 in cmake
### 2. `imx95-a55-evk: add USDHC eMMC driver support`
- Create `imx95_pinmux.h` / `imx95_ccm.h` / `imx95_pll.h` hardware
definitions for imx95
- Add USDHC1 8-bit eMMC pin mux and clock macros to `board.h`
- Create board-level `imx9_usdhc.c` glue code
- Update `imx9_bringup.c` with DMA allocator and USDHC init
- Add `CONFIG_IMX9_CLK_OVER_SCMI` compile-time guards in `imx9_usdhc.c` to
isolate the IMX95 SCMI clock path from the existing IMX93 direct-CCM path — no
functional change for IMX93
### 3. `imx9: usdhc fix dmapreflight rejecting small unaligned buffers`
- `imx9_dmapreflight()` rejected unaligned buffers unconditionally, but
`dmarecvsetup()` has a bounce path via `priv->rxbuffer` for small transfers
- Add a `buflen > sizeof(priv->rxbuffer)` check so that small reads (e.g.
ext_csd 512-byte stack buffer) can use the bounce buffer instead of failing
with `-EFAULT`
### 4. `imx95-a55-evk: add MBR/GPT partition table parsing on eMMC`
- Parse the partition table on `/dev/mmcsd0` during board bringup and
register each partition as `/dev/mmcsd0pN`
- Add custom MBR handler for unnamed partition entries
## Impact
- IMX93 code paths are fully preserved behind `#ifndef
CONFIG_IMX9_CLK_OVER_SCMI` guards — zero functional change for existing IMX93
boards
- The `dmapreflight` fix is a generic improvement that benefits all imx9
USDHC users
- If using i.mx95-FRDM EVK, able to mount the /boot partition same with
uboot/linux, after patch.
## Testing
Verified on i.MX95 FRDM EVK:
- eMMC device recognized and initialized (8-bit mode)
- Partition table parsed, partitions registered
- `mount -t vfat /dev/mmcsd0p0 /data` works
```bash
nsh> mount -t vfat /dev/mmcsd0p0 /data
nsh> ls -l /data/nuttx.bin
-rw-rw-rw- 515184 /data/nuttx.bin
```
ostest passed in i.MX95 FRDM EVK
```
[2026-03-06 17:57:11] user_main: Exiting
[2026-03-06 17:57:11] ostest_main: Exiting with status 0
[2026-03-06 17:57:11] nsh>
```
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