dcgong2917 opened a new pull request, #19842:
URL: https://github.com/apache/nuttx/pull/19842
## Summary
Add a shared NuttX SPI master lower-half for the Realtek Ameba SPI
(DesignWare SSI) controllers and wire it into three chips. The driver is
IC-agnostic: it lives in `arch/arm/src/common/ameba/ameba_spi.c` and is
driven through the SDK fwlib in polling mode with full-duplex exchange and
a software chip-select. Each port supplies only a same-named per-chip
header
(`ameba_spi_chip.h`) with the controller count, register bases, clock
masks,
crossbar pad-mux codes and the SSI clock query; the buses register as
`/dev/spiN`.
All three chips clock the SSI from the same conceptual source -- the
peripheral `ip_clk` that the SPI baud divider divides down to make SCLK.
The
shared driver only needs that frequency (it calls the `AMEBA_SPI_IPCLK()`
macro), but the fwlib API and clock-divider register that expose it differ
per chip, so each per-chip header supplies its own expansion:
* **rtl8721dx** — the shared driver + per-chip header;
`ip_clk = PLL_ClkGet() / (HPERI divider + 1)`, divider in
REG_LSYS_CKD_GRP0.
* **rtl8720f** — per-chip header using `SYS_PLL_ClkGet()` (this SDK has no
`PLL_ClkGet()`) with the divider field in REG_LSYS_CKD_SYS_PLL_GRP0;
single
port-A controller.
* **rtl8721f** — per-chip header whose SDK exposes the HPERI
clock directly via `HPERI_ClkGet()`, so no divider register read is
needed.
`tools/nxstyle.c` gains the `SSI_`/`PLL_`/`HPERI_`/`SYS_PLL_` vendor
prefixes
in the existing Ameba SDK-symbol allow-list, matching how the earlier
UART/I2C
ports handle their SDK ROM/HAL names.
## Impact
New optional feature (`CONFIG_AMEBA_SPI`), off by default. No change to any
existing configuration or driver. Adds an `spi` board configuration to each
board for validation. Depends only on the already-merged Ameba
GPIO/UART/I2C
support.
## Testing
Built and hardware-verified on each board with the `spi` config and the
`system/spi` spitool, MOSI shorted to MISO for loopback (`spi exch` returns
sent == received):
* **pke8721daf (RTL8721DX)** — SPI on PB18-21, loopback passes across
8/16-bit,
variable frequency, mode 3 and long transfers.
* **rtl8720f_evb (RTL8720F)** — SPI0 on PA14-17 (single port-A controller),
`spi exch -b 0 -x 8 deadbeef` returns `DE AD BE EF ...`.
* **rtl8721f_evb (RTL8721F)** — two independent buses, SPI0 on PA14-17 and
SPI1 on PB13-16, both loopback pass.
`tools/checkpatch.sh -g master..HEAD` reports no errors.
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