renesas-ra: Add the UART methods uart.txdone() and uart.flush().

This required to add two functions down the stack to uart.c and ra.sci.c.

- One for telling, whther the transmission is busy.
- One for reporting the size of the TX buffer.

Tested with a EK-RA6M2 board.

docs/library/machine.UART.rst

@@ -188,7 +188,7 @@ Methods
        For the rp2, esp8266 and nrf ports the call returns while the last byte is sent.
        If required, a one character wait time has to be added in the calling script.
 
-   Availability: rp2, esp32, esp8266, mimxrt, cc3200, stm32, nrf ports
+   Availability: rp2, esp32, esp8266, mimxrt, cc3200, stm32, nrf ports, renesas-ra
 
 .. method:: UART.txdone()
 
@@ -201,7 +201,7 @@ Methods
        of a transfer is still being sent. If required, a one character wait time has to be
        added in the calling script.
 
-   Availability: rp2, esp32, esp8266, mimxrt, cc3200, stm32, nrf ports
+   Availability: rp2, esp32, esp8266, mimxrt, cc3200, stm32, nrf ports, renesas-ra
 
 Constants
 ---------

ports/renesas-ra/machine_uart.c

@@ -409,6 +409,14 @@ STATIC mp_obj_t machine_uart_sendbreak(mp_obj_t self_in) {
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(machine_uart_sendbreak_obj, machine_uart_sendbreak);
 
+// \method uart.txdone()
+// Return `True` if all characters have been sent.
+STATIC mp_obj_t machine_uart_txdone(mp_obj_t self_in) {
+    machine_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
+    return uart_tx_busy(self) ? mp_const_false : mp_const_true;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(machine_uart_txdone_obj, machine_uart_txdone);
+
 // irq(handler, trigger, hard)
 STATIC mp_obj_t machine_uart_irq(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     mp_arg_val_t args[MP_IRQ_ARG_INIT_NUM_ARGS];
@@ -452,6 +460,8 @@ STATIC const mp_rom_map_elem_t machine_uart_locals_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_init), MP_ROM_PTR(&machine_uart_init_obj) },
     { MP_ROM_QSTR(MP_QSTR_deinit), MP_ROM_PTR(&machine_uart_deinit_obj) },
     { MP_ROM_QSTR(MP_QSTR_any), MP_ROM_PTR(&machine_uart_any_obj) },
+    { MP_ROM_QSTR(MP_QSTR_txdone), MP_ROM_PTR(&machine_uart_txdone_obj) },
+    { MP_ROM_QSTR(MP_QSTR_flush), MP_ROM_PTR(&mp_stream_flush_obj) },
 
     /// \method read([nbytes])
     { MP_ROM_QSTR(MP_QSTR_read), MP_ROM_PTR(&mp_stream_read_obj) },
@@ -557,6 +567,19 @@ STATIC mp_uint_t machine_uart_ioctl(mp_obj_t self_in, mp_uint_t request, uintptr
         if ((flags & MP_STREAM_POLL_WR) && uart_tx_avail(self)) {
             ret |= MP_STREAM_POLL_WR;
         }
+    } else if (request == MP_STREAM_FLUSH) {
+        // The timeout is estimated using the buffer size and the baudrate.
+        // Take the worst case assumptions at 13 bit symbol size times 2.
+        uint32_t timeout = mp_hal_ticks_ms() +
+            (uint32_t)(uart_tx_txbuf(self)) * 13000ll * 2 / self->baudrate;
+        do {
+            if (!uart_tx_busy(self)) {
+                return 0;
+            }
+            MICROPY_EVENT_POLL_HOOK
+        } while (mp_hal_ticks_ms() < timeout);
+        *errcode = MP_ETIMEDOUT;
+        ret = MP_STREAM_ERROR;
     } else {
         *errcode = MP_EINVAL;
         ret = MP_STREAM_ERROR;

ports/renesas-ra/ra/ra_sci.c

@@ -1026,6 +1026,16 @@ int ra_sci_tx_wait(uint32_t ch) {
     return (int)(tx_fifo[idx].len != (tx_fifo[idx].size - 1));
 }
 
+int ra_sci_tx_busy(uint32_t ch) {
+    uint32_t idx = ch_to_idx[ch];
+    return (int)(tx_fifo[idx].busy);
+}
+
+int ra_sci_tx_bufsize(uint32_t ch) {
+    uint32_t idx = ch_to_idx[ch];
+    return (int)(tx_fifo[idx].size - 1);
+}
+
 void ra_sci_tx_break(uint32_t ch) {
     uint32_t idx = ch_to_idx[ch];
     R_SCI0_Type *sci_reg = sci_regs[idx];

ports/renesas-ra/ra/ra_sci.h

@@ -52,6 +52,8 @@ bool ra_sci_is_rxirq_enable(uint32_t ch);
 void ra_sci_isr_te(uint32_t ch);
 int ra_sci_rx_ch(uint32_t ch);
 int ra_sci_rx_any(uint32_t ch);
+int ra_sci_tx_busy(uint32_t ch);
+int ra_sci_tx_bufsize(uint32_t ch);
 void ra_sci_tx_ch(uint32_t ch, int c);
 int ra_sci_tx_wait(uint32_t ch);
 void ra_sci_tx_break(uint32_t ch);

ports/renesas-ra/uart.c

@@ -420,6 +420,16 @@ mp_uint_t uart_tx_avail(machine_uart_obj_t *self) {
     return ra_sci_tx_wait(ch);
 }
 
+mp_uint_t uart_tx_busy(machine_uart_obj_t *self) {
+    int ch = (int)self->uart_id;
+    return ra_sci_tx_busy(ch);
+}
+
+mp_uint_t uart_tx_txbuf(machine_uart_obj_t *self) {
+    int ch = (int)self->uart_id;
+    return ra_sci_tx_bufsize(ch);
+}
+
 // Waits at most timeout milliseconds for at least 1 char to become ready for
 // reading (from buf or for direct reading).
 // Returns true if something available, false if not.

ports/renesas-ra/uart.h

@@ -106,6 +106,8 @@ void uart_attach_to_repl(machine_uart_obj_t *self, bool attached);
 uint32_t uart_get_baudrate(machine_uart_obj_t *self);
 mp_uint_t uart_rx_any(machine_uart_obj_t *uart_obj);
 mp_uint_t uart_tx_avail(machine_uart_obj_t *uart_obj);
+mp_uint_t uart_tx_busy(machine_uart_obj_t *uart_obj);
+mp_uint_t uart_tx_txbuf(machine_uart_obj_t *self);
 bool uart_rx_wait(machine_uart_obj_t *self, uint32_t timeout);
 int uart_rx_char(machine_uart_obj_t *uart_obj);
 bool uart_tx_wait(machine_uart_obj_t *self, uint32_t timeout);