dcgong2917 opened a new pull request, #20020:
URL: https://github.com/apache/nuttx/pull/20020
## Summary
This PR adds a shared NuttX timer lower-half for the Realtek Ameba
general-purpose timers and wires it into three boards (RTL8721Dx, RTL8720F,
RTL8721F).
The shared driver (`arch/arm/src/common/ameba/ameba_timer.c`) sits on the
SDK
per-chip instance table (`ameba_timer_chip.h`) for each timer's base
address,
input clock, RCC gate mask and IRQ; the requested period is programmed
directly in microseconds and converted to the 32-bit auto-reload with a
single
clkfreq formula. The RTIM time-base entry points resolve to ROM, while the
interrupt-clear and period-change helpers come from the fwlib RAM source
`ameba_tim.c` (shared with the existing PWM driver, now also pulled in by
`CONFIG_AMEBA_TIMER`, matching the PWM build rule).
On each board two of the 32.768 kHz "basic" (LTIM) timers are exposed:
`/dev/timer0` is TIM1 and `/dev/timer1` is TIM2. TIM0 is deliberately left
untouched because the boot ROM claims it as the always-on system timer
(SYSTIMER); reprogramming it would break every SDK delay. Only the per-chip
base addresses, RCC masks and IRQs differ between the three SoCs, so each
chip
adds only a small `ameba_timer_chip.h` (verified against the SoC
`hal_platform.h` / `sysreg_lsys.h` / vector table) plus its build hooks,
board
bring-up registration, board `timer` defconfig and `index.rst` docs. The
shared driver itself is identical across all three.
The `timer` defconfigs also enable `CONFIG_TIMER_ARCH=y`; without it
`up_timer_set_lowerhalf()` expands to a no-op macro,
`systick_initialize()` is
never called and `clock_systime_ticks()` never advances.
`tools/nxstyle.c` gains the vendor `RTIM_` symbol prefix in the whitelist,
alongside the existing `RCC_` / `SYSTIMER_` Ameba SDK entries.
## Impact
New optional peripheral driver, off by default (`CONFIG_AMEBA_TIMER`). No
change to any existing board configuration. Only affects the three Ameba
boards listed above.
## Testing
- `nxstyle` / `checkpatch` clean on all three commits.
- `make` and `cmake` out-of-tree builds pass for all three boards with the
`:timer` config.
- Hardware-verified on RTL8721F, RTL8720F and RTL8721Dx with
`examples/timer`
against both `/dev/timer0` and `/dev/timer1`: the update interrupt fires
at
the requested 1 s interval (cross-checked against the independent ROM
SYSTIMER = 32768 ticks = 1.000 s), and `cat /proc/uptime` advances in
real
time (the example completes in ~2 s with nsignals=2, confirming the
system
tick is running).
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