dcgong2917 opened a new pull request, #19582:
URL: https://github.com/apache/nuttx/pull/19582
## Summary
Adds GPIO character-driver support for the RTL8721F (amebagreen2) and the
RTL8721F EVB board, plus a fix to the shared Ameba GPIO ISR that this port
uncovered on hardware.
Two commits:
1. **arch/arm/common/ameba: fix level-triggered GPIO interrupt storm**
The shared port ISR clears interrupt status with
`GPIO_INTStatusClearEdge()`, which only clears edge latches. For a
level-triggered pin the status stays asserted while the level is active,
so the ISR re-enters forever once the level fires — the system hangs
before the application can service the event. The pin is now masked in
the ISR before the callback and re-enabled by the application via
`go_enable()`. Edge pins are unchanged. This also affects RTL8721Dx
(already in-tree).
2. **arch/arm/rtl8721f: add GPIO character driver support**
Wires the shared `ameba_gpio.c` into the RTL8721F build (three GPIO
ports A/B/C), adds the chip header, board glue, a minimal `gpio` NSH
defconfig, and documentation. On amebagreen2 the ROM `GPIO_Init` does
not call `PAD_PullCtrl`/`GPIO_INTMode`, so the driver now calls both
explicitly (harmless redundant writes on RTL8721Dx).
## Impact
- New feature for RTL8721F; no impact on other architectures.
- Behavioural fix for level-triggered GPIO interrupts on all Ameba ARM
chips (RTL8721Dx, RTL8721F). Edge-triggered and non-interrupt GPIO
behaviour is unchanged.
- New board config: `rtl8721f_evb/gpio`.
## Testing
Hardware-verified on the RTL8721F EVB (`rtl8721f_evb/gpio` config) via
`apps/examples/gpio`:
- Output pin (PA25): drive high/low, read-back confirmed.
- Input pin (PA24): read high/low confirmed.
- Interrupt pin (PA26): all trigger/polarity combinations exercised —
rising edge, falling edge, level high, level low. Level cases confirmed
the storm fix (system survives; without the fix it hangs).
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