arch/arm/ameba: add shared timer driver for RTL8721Dx/RTL8720F/RTL8721F

Documentation/platforms/arm/rtl8720f/boards/rtl8720f_evb/index.rst

@@ -47,6 +47,8 @@ Supported in this NuttX port:
   alarm support, driven directly on the SDK fwlib register layer
 * On-chip watchdog exposed as a ``/dev/watchdog0`` character device, driven
   directly on the SDK fwlib register layer
+* General-purpose timers exposed as ``/dev/timer0`` and ``/dev/timer1``
+  character devices, driven directly on the SDK fwlib register layer
 
 Buttons and LEDs
 ================
@@ -190,6 +192,20 @@ which opens the device, sets a timeout, and pings it::
 
     nsh> wdog                            # run the watchdog example
 
+timer
+-----
+
+Minimal NSH with the on-chip general-purpose timer driver and the ``timer``
+example enabled (no Wi-Fi). Two 32-bit basic timers clocked at 32.768 kHz are
+registered from the board bring-up
+(``boards/arm/rtl8720f/rtl8720f_evb/src/rtl8720f_timer.c``) as ``/dev/timer0``
+(TIM1) and ``/dev/timer1`` (TIM2); they have no board wiring (they are
+internal). TIM0 is reserved by the boot ROM as the system timer and is not
+exposed. Exercise a device with the example, which sets an interval and counts
+the update interrupts::
+
+    nsh> timer -d /dev/timer0            # run the timer example on TIM1
+
 nsh
 ---
 

Documentation/platforms/arm/rtl8721dx/boards/pke8721daf/index.rst

@@ -49,6 +49,8 @@ Supported in this NuttX port:
   alarm support, driven directly on the SDK fwlib register layer
 * On-chip watchdog exposed as a ``/dev/watchdog0`` character device, driven
   directly on the SDK fwlib register layer
+* General-purpose timers exposed as ``/dev/timer0`` and ``/dev/timer1``
+  character devices, driven directly on the SDK fwlib register layer
 
 Buttons and LEDs
 ================
@@ -199,6 +201,20 @@ which opens the device, sets a timeout, and pings it::
 
     nsh> wdog                            # run the watchdog example
 
+timer
+-----
+
+Minimal NSH with the on-chip general-purpose timer driver and the ``timer``
+example enabled (no Wi-Fi). Two 32-bit basic timers clocked at 32.768 kHz are
+registered from the board bring-up
+(``boards/arm/rtl8721dx/pke8721daf/src/rtl8721dx_timer.c``) as ``/dev/timer0``
+(TIM1) and ``/dev/timer1`` (TIM2); they have no board wiring (they are
+internal). TIM0 is reserved by the boot ROM as the system timer and is not
+exposed. Exercise a device with the example, which sets an interval and counts
+the update interrupts::
+
+    nsh> timer -d /dev/timer0            # run the timer example on TIM1
+
 Wi-Fi
 =====
 

Documentation/platforms/arm/rtl8721f/boards/rtl8721f_evb/index.rst

@@ -48,6 +48,8 @@ Supported in this NuttX port:
   alarm support, driven directly on the SDK fwlib register layer
 * On-chip watchdog exposed as a ``/dev/watchdog0`` character device, driven
   directly on the SDK fwlib register layer
+* General-purpose timers exposed as ``/dev/timer0`` and ``/dev/timer1``
+  character devices, driven directly on the SDK fwlib register layer
 
 Buttons and LEDs
 ================
@@ -193,6 +195,20 @@ which opens the device, sets a timeout, and pings it::
 
     nsh> wdog                            # run the watchdog example
 
+timer
+-----
+
+Minimal NSH with the on-chip general-purpose timer driver and the ``timer``
+example enabled (no Wi-Fi). Two 32-bit basic timers clocked at 32.768 kHz are
+registered from the board bring-up
+(``boards/arm/rtl8721f/rtl8721f_evb/src/rtl8721f_timer.c``) as ``/dev/timer0``
+(TIM1) and ``/dev/timer1`` (TIM2); they have no board wiring (they are
+internal). TIM0 is reserved by the boot ROM as the system timer and is not
+exposed. Exercise a device with the example, which sets an interval and counts
+the update interrupts::
+
+    nsh> timer -d /dev/timer0            # run the timer example on TIM1
+
 nsh
 ---
 

arch/arm/src/common/ameba/Kconfig

@@ -149,4 +149,21 @@ config AMEBA_WDG
 		enabled, so stop() arms the WDG early interrupt and refreshes the
 		counter from its handler to inhibit the reset.
 
+config AMEBA_TIMER
+	bool "Timer"
+	default n
+	select TIMER
+	---help---
+		Expose the Ameba general-purpose timers as NuttX timer devices at
+		/dev/timerN (start/stop/settimeout/getstatus, plus a periodic
+		expiration callback).  The timeout is programmed directly in
+		microseconds.
+
+		The driver (arch/arm/src/common/ameba/ameba_timer.c) is a
+		parameterised lower half sitting on the SDK fwlib RTIM register
+		layer; the board picks which of the twelve on-chip timers to expose
+		via the per-chip instance table.  On the pke8721daf /dev/timer0 is
+		TIM1 and /dev/timer1 is TIM2, both 32.768 kHz basic timers.  TIM0
+		is reserved by the ROM as the system timer and is not exposed.
+
 endmenu # Ameba Peripheral Support