bsps: Move libchip to bsps

This patch is a part of the BSP source reorganization.

Update #3285.

1 files changed, 814 insertions, 0 deletions

diff --git a/bsps/shared/dev/serial/ns16550-context.c b/bsps/shared/dev/serial/ns16550-context.c
new file mode 100644
index 0000000000..b42be96a26
--- /dev/null
+++ b/bsps/shared/dev/serial/ns16550-context.c
@@ -0,0 +1,814 @@
+/**
+ *  @file
+ *  
+ *  This file contains the TTY driver for the National Semiconductor NS16550.
+ *
+ *  This part is widely cloned and second sourced.  It is found in a number
+ *  of "Super IO" controllers.
+ *
+ *  This driver uses the termios pseudo driver.
+ */
+
+/*
+ *  COPYRIGHT (c) 1998 by Radstone Technology
+ *
+ *  THIS FILE IS PROVIDED TO YOU, THE USER, "AS IS", WITHOUT WARRANTY OF ANY
+ *  KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE
+ *  IMPLIED WARRANTY OF FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK
+ *  AS TO THE QUALITY AND PERFORMANCE OF ALL CODE IN THIS FILE IS WITH YOU.
+ *
+ *  You are hereby granted permission to use, copy, modify, and distribute
+ *  this file, provided that this notice, plus the above copyright notice
+ *  and disclaimer, appears in all copies. Radstone Technology will provide
+ *  no support for this code.
+ *
+ *  COPYRIGHT (c) 1989-2012.
+ *  On-Line Applications Research Corporation (OAR).
+ *
+ *  The license and distribution terms for this file may be
+ *  found in the file LICENSE in this distribution or at
+ *  http://www.rtems.org/license/LICENSE.
+ */
+
+#include <stdlib.h>
+
+#include <rtems/bspIo.h>
+
+#include <bsp.h>
+
+#include <libchip/ns16550.h>
+#include <libchip/ns16550_p.h>
+
+#if defined(BSP_FEATURE_IRQ_EXTENSION)
+  #include <bsp/irq.h>
+#elif defined(BSP_FEATURE_IRQ_LEGACY)
+  #include <bsp/irq.h>
+#elif defined(__PPC__) || defined(__i386__)
+  #include <bsp/irq.h>
+  #define BSP_FEATURE_IRQ_LEGACY
+  #ifdef BSP_SHARED_HANDLER_SUPPORT
+    #define BSP_FEATURE_IRQ_LEGACY_SHARED_HANDLER_SUPPORT
+  #endif
+#endif
+
+static uint32_t NS16550_GetBaudDivisor(ns16550_context *ctx, uint32_t baud)
+{
+  uint32_t clock = ctx->clock;
+  uint32_t baudDivisor = (clock != 0 ? clock : 115200) / (baud * 16);
+
+  if (ctx->has_fractional_divider_register) {
+    uint32_t fractionalDivider = 0x10;
+    uint32_t err = baud;
+    uint32_t mulVal;
+    uint32_t divAddVal;
+
+    clock /= 16 * baudDivisor;
+    for (mulVal = 1; mulVal < 16; ++mulVal) {
+      for (divAddVal = 0; divAddVal < mulVal; ++divAddVal) {
+        uint32_t actual = (mulVal * clock) / (mulVal + divAddVal);
+        uint32_t newErr = actual > baud ? actual - baud : baud - actual;
+
+        if (newErr < err) {
+          err = newErr;
+          fractionalDivider = (mulVal << 4) | divAddVal;
+        }
+      }
+    }
+
+    (*ctx->set_reg)(
+      ctx->port,
+      NS16550_FRACTIONAL_DIVIDER,
+      fractionalDivider
+    );
+  }
+
+  return baudDivisor;
+}
+
+/*
+ *  ns16550_enable_interrupts
+ *
+ *  This routine initializes the port to have the specified interrupts masked.
+ */
+static void ns16550_enable_interrupts(
+  ns16550_context *ctx,
+  int              mask
+)
+{
+  (*ctx->set_reg)(ctx->port, NS16550_INTERRUPT_ENABLE, mask);
+}
+
+static void ns16550_clear_and_set_interrupts(
+  ns16550_context *ctx,
+  uint8_t          clear,
+  uint8_t          set
+)
+{
+  rtems_interrupt_lock_context lock_context;
+  ns16550_get_reg get_reg = ctx->get_reg;
+  ns16550_set_reg set_reg = ctx->set_reg;
+  uintptr_t port = ctx->port;
+  uint8_t val;
+
+  rtems_termios_device_lock_acquire(&ctx->base, &lock_context);
+  val = (*get_reg)(port, NS16550_INTERRUPT_ENABLE);
+  val &= ~clear;
+  val |= set;
+  (*set_reg)(port, NS16550_INTERRUPT_ENABLE, val);
+  rtems_termios_device_lock_release(&ctx->base, &lock_context);
+}
+
+/*
+ *  ns16550_probe
+ */
+
+bool ns16550_probe(rtems_termios_device_context *base)
+{
+  ns16550_context        *ctx = (ns16550_context *) base;
+  uintptr_t               pNS16550;
+  uint8_t                 ucDataByte;
+  uint32_t                ulBaudDivisor;
+  ns16550_set_reg         setReg;
+  ns16550_get_reg         getReg;
+
+  ctx->modem_control = SP_MODEM_IRQ;
+
+  pNS16550 = ctx->port;    
+  setReg   = ctx->set_reg;
+  getReg   = ctx->get_reg;
+
+  /* Clear the divisor latch, clear all interrupt enables,
+   * and reset and
+   * disable the FIFO's.
+   */
+
+  (*setReg)(pNS16550, NS16550_LINE_CONTROL, 0x0);
+  ns16550_enable_interrupts(ctx, NS16550_DISABLE_ALL_INTR );
+
+  /* Set the divisor latch and set the baud rate. */
+
+  ulBaudDivisor = NS16550_GetBaudDivisor(ctx, ctx->initial_baud);
+  ctx->baud_divisor = ulBaudDivisor;
+  ucDataByte = SP_LINE_DLAB;
+  (*setReg)(pNS16550, NS16550_LINE_CONTROL, ucDataByte);
+
+  /* XXX */
+  (*setReg)(pNS16550,NS16550_TRANSMIT_BUFFER,(uint8_t)(ulBaudDivisor & 0xffU));
+  (*setReg)(
+    pNS16550,NS16550_INTERRUPT_ENABLE,
+    (uint8_t)(( ulBaudDivisor >> 8 ) & 0xffU )
+  );
+
+  /* Clear the divisor latch and set the character size to eight bits */
+  /* with one stop bit and no parity checking. */
+  ucDataByte = EIGHT_BITS;
+  ctx->line_control = ucDataByte;
+  (*setReg)(pNS16550, NS16550_LINE_CONTROL, ucDataByte);
+
+  /* Enable and reset transmit and receive FIFOs. TJA     */
+  ucDataByte = SP_FIFO_ENABLE;
+  (*setReg)(pNS16550, NS16550_FIFO_CONTROL, ucDataByte);
+
+  ucDataByte = SP_FIFO_ENABLE | SP_FIFO_RXRST | SP_FIFO_TXRST;
+  (*setReg)(pNS16550, NS16550_FIFO_CONTROL, ucDataByte);
+
+  ns16550_enable_interrupts(ctx, NS16550_DISABLE_ALL_INTR);
+
+  /* Set data terminal ready. */
+  /* And open interrupt tristate line */
+  (*setReg)(pNS16550, NS16550_MODEM_CONTROL,ctx->modem_control);
+
+  (*getReg)(pNS16550, NS16550_LINE_STATUS );
+  (*getReg)(pNS16550, NS16550_RECEIVE_BUFFER );
+
+  return true;
+}
+
+static size_t ns16550_write_to_fifo(
+  const ns16550_context *ctx,
+  const char *buf,
+  size_t len
+)
+{
+  uintptr_t port = ctx->port;
+  ns16550_set_reg set = ctx->set_reg;
+  size_t out = len > SP_FIFO_SIZE ? SP_FIFO_SIZE : len;
+  size_t i;
+
+  for (i = 0; i < out; ++i) {
+    (*set)(port, NS16550_TRANSMIT_BUFFER, buf[i]);
+  }
+
+  return out;
+}
+
+/**
+ * @brief Process interrupt.
+ */
+static void ns16550_isr(void *arg)
+{
+  rtems_termios_tty *tty = arg;
+  ns16550_context *ctx = rtems_termios_get_device_context(tty);
+  uintptr_t port = ctx->port;
+  ns16550_get_reg get = ctx->get_reg;
+  int i = 0;
+  char buf [SP_FIFO_SIZE];
+
+  /* Iterate until no more interrupts are pending */
+  do {
+    /* Fetch received characters */
+    for (i = 0; i < SP_FIFO_SIZE; ++i) {
+      if ((get( port, NS16550_LINE_STATUS) & SP_LSR_RDY) != 0) {
+        buf [i] = (char) get(port, NS16550_RECEIVE_BUFFER);
+      } else {
+        break;
+      }
+    }
+
+    /* Enqueue fetched characters */
+    rtems_termios_enqueue_raw_characters(tty, buf, i);
+
+    /* Do transmit */
+    if (ctx->out_total > 0
+        && (get(port, NS16550_LINE_STATUS) & SP_LSR_THOLD) != 0) {
+      size_t current = ctx->out_current;
+
+      ctx->out_buf += current;
+      ctx->out_remaining -= current;
+
+      if (ctx->out_remaining > 0) {
+        ctx->out_current =
+          ns16550_write_to_fifo(ctx, ctx->out_buf, ctx->out_remaining);
+      } else {
+        rtems_termios_dequeue_characters(tty, ctx->out_total);
+      }
+    }
+  } while ((get( port, NS16550_INTERRUPT_ID) & SP_IID_0) == 0);
+}
+
+static void ns16550_isr_task(void *arg)
+{
+  rtems_termios_tty *tty = arg;
+  ns16550_context *ctx = rtems_termios_get_device_context(tty);
+  uint8_t status = (*ctx->get_reg)(ctx->port, NS16550_LINE_STATUS);
+
+  if ((status & SP_LSR_RDY) != 0) {
+    ns16550_clear_and_set_interrupts(ctx, SP_INT_RX_ENABLE, 0);
+    rtems_termios_rxirq_occured(tty);
+  }
+
+  if (ctx->out_total > 0 && (status & SP_LSR_THOLD) != 0) {
+    size_t current = ctx->out_current;
+
+    ctx->out_buf += current;
+    ctx->out_remaining -= current;
+
+    if (ctx->out_remaining > 0) {
+      ctx->out_current =
+        ns16550_write_to_fifo(ctx, ctx->out_buf, ctx->out_remaining);
+    } else {
+      size_t done = ctx->out_total;
+
+      ctx->out_total = 0;
+      ns16550_clear_and_set_interrupts(ctx, SP_INT_TX_ENABLE, 0);
+      rtems_termios_dequeue_characters(tty, done);
+    }
+  }
+}
+
+static int ns16550_read_task(rtems_termios_device_context *base)
+{
+  ns16550_context *ctx = (ns16550_context *) base;
+  uintptr_t port = ctx->port;
+  ns16550_get_reg get = ctx->get_reg;
+  char buf[SP_FIFO_SIZE];
+  int i;
+
+  for (i = 0; i < SP_FIFO_SIZE; ++i) {
+    if ((get(port, NS16550_LINE_STATUS) & SP_LSR_RDY) != 0) {
+      buf[i] = (char) get(port, NS16550_RECEIVE_BUFFER);
+    } else {
+      break;
+    }
+  }
+
+  rtems_termios_enqueue_raw_characters(ctx->tty, buf, i);
+  ns16550_clear_and_set_interrupts(ctx, 0, SP_INT_RX_ENABLE);
+
+  return -1;
+}
+
+/*
+ *  ns16550_initialize_interrupts
+ *
+ *  This routine initializes the port to operate in interrupt driver mode.
+ */
+static void ns16550_initialize_interrupts(
+  struct rtems_termios_tty *tty,
+  ns16550_context          *ctx,
+  void                    (*isr)(void *)
+)
+{
+  #ifdef BSP_FEATURE_IRQ_EXTENSION
+    {
+      rtems_status_code sc = RTEMS_SUCCESSFUL;
+      sc = rtems_interrupt_handler_install(
+        ctx->irq,
+        "NS16550",
+        RTEMS_INTERRUPT_SHARED,
+        isr,
+        tty
+      );
+      if (sc != RTEMS_SUCCESSFUL) {
+        /* FIXME */
+        printk( "%s: Error: Install interrupt handler\n", __func__);
+        rtems_fatal_error_occurred( 0xdeadbeef);
+      }
+    }
+  #elif defined(BSP_FEATURE_IRQ_LEGACY)
+    {
+      int rv = 0;
+      #ifdef BSP_FEATURE_IRQ_LEGACY_SHARED_HANDLER_SUPPORT
+        rtems_irq_connect_data cd = {
+          ctx->irq,
+          isr,
+          tty,
+          NULL,
+          NULL,
+          NULL,
+          NULL
+        };
+        rv = BSP_install_rtems_shared_irq_handler( &cd);
+      #else
+        rtems_irq_connect_data cd = {
+          ctx->irq,
+          isr,
+          tty,
+          NULL,
+          NULL,
+          NULL
+        };
+        rv = BSP_install_rtems_irq_handler( &cd);
+      #endif
+      if (rv == 0) {
+        /* FIXME */
+        printk( "%s: Error: Install interrupt handler\n", __func__);
+        rtems_fatal_error_occurred( 0xdeadbeef);
+      }
+    }
+  #endif
+}
+
+/*
+ *  ns16550_open
+ */
+
+static bool ns16550_open(
+  struct rtems_termios_tty      *tty,
+  rtems_termios_device_context  *base,
+  struct termios                *term,
+  rtems_libio_open_close_args_t *args
+)
+{
+  ns16550_context *ctx = (ns16550_context *) base;
+
+  ctx->tty = tty;
+
+  /* Set initial baud */
+  rtems_termios_set_initial_baud(tty, ctx->initial_baud);
+
+  if (tty->handler.mode == TERMIOS_IRQ_DRIVEN) {
+    ns16550_initialize_interrupts(tty, ctx, ns16550_isr);
+    ns16550_enable_interrupts(ctx, NS16550_ENABLE_ALL_INTR_EXCEPT_TX);
+  } else if (tty->handler.mode == TERMIOS_TASK_DRIVEN) {
+    ns16550_initialize_interrupts(tty, ctx, ns16550_isr_task);
+    ns16550_enable_interrupts(ctx, NS16550_ENABLE_ALL_INTR_EXCEPT_TX);
+  }
+
+  return true;
+}
+
+static void ns16550_cleanup_interrupts(
+  struct rtems_termios_tty *tty,
+  ns16550_context          *ctx,
+  void                    (*isr)(void *)
+)
+{
+  #if defined(BSP_FEATURE_IRQ_EXTENSION)
+    rtems_status_code sc = RTEMS_SUCCESSFUL;
+    sc = rtems_interrupt_handler_remove(
+      ctx->irq,
+      isr,
+      tty
+    );
+    if (sc != RTEMS_SUCCESSFUL) {
+      /* FIXME */
+      printk("%s: Error: Remove interrupt handler\n", __func__);
+      rtems_fatal_error_occurred(0xdeadbeef);
+    }
+  #elif defined(BSP_FEATURE_IRQ_LEGACY)
+    int rv = 0;
+    rtems_irq_connect_data cd = {
+      .name = ctx->irq,
+      .hdl = isr,
+      .handle = tty
+    };
+    rv = BSP_remove_rtems_irq_handler(&cd);
+    if (rv == 0) {
+      /* FIXME */
+      printk("%s: Error: Remove interrupt handler\n", __func__);
+      rtems_fatal_error_occurred(0xdeadbeef);
+    }
+  #endif
+}
+
+/*
+ *  ns16550_close
+ */
+
+static void ns16550_close(
+  struct rtems_termios_tty      *tty,
+  rtems_termios_device_context  *base,
+  rtems_libio_open_close_args_t *args
+)
+{
+  ns16550_context *ctx = (ns16550_context *) base;
+
+  ns16550_enable_interrupts(ctx, NS16550_DISABLE_ALL_INTR);
+
+  if (tty->handler.mode == TERMIOS_IRQ_DRIVEN) {
+    ns16550_cleanup_interrupts(tty, ctx, ns16550_isr);
+  } else if (tty->handler.mode == TERMIOS_TASK_DRIVEN) {
+    ns16550_cleanup_interrupts(tty, ctx, ns16550_isr_task);
+  }
+}
+
+/**
+ * @brief Polled write for NS16550.
+ */
+void ns16550_polled_putchar(rtems_termios_device_context *base, char out)
+{
+  ns16550_context *ctx = (ns16550_context *) base;
+  uintptr_t port = ctx->port;
+  ns16550_get_reg get = ctx->get_reg;
+  ns16550_set_reg set = ctx->set_reg;
+  uint32_t status = 0;
+  rtems_interrupt_lock_context lock_context;
+
+  /* Save port interrupt mask */
+  uint32_t interrupt_mask = get( port, NS16550_INTERRUPT_ENABLE);
+
+  /* Disable port interrupts */
+  ns16550_enable_interrupts(ctx, NS16550_DISABLE_ALL_INTR);
+
+  while (true) {
+    /* Try to transmit the character in a critical section */
+    rtems_termios_device_lock_acquire(&ctx->base, &lock_context);
+
+    /* Read the transmitter holding register and check it */
+    status = get( port, NS16550_LINE_STATUS);
+    if ((status & SP_LSR_THOLD) != 0) {
+      /* Transmit character */
+      set( port, NS16550_TRANSMIT_BUFFER, out);
+
+      /* Finished */
+      rtems_termios_device_lock_release(&ctx->base, &lock_context);
+      break;
+    } else {
+      rtems_termios_device_lock_release(&ctx->base, &lock_context);
+    }
+
+    /* Wait for transmitter holding register to be empty */
+    do {
+      status = get( port, NS16550_LINE_STATUS);
+    } while ((status & SP_LSR_THOLD) == 0);
+  }
+
+  /* Restore port interrupt mask */
+  set( port, NS16550_INTERRUPT_ENABLE, interrupt_mask);
+}
+
+/*
+ * These routines provide control of the RTS and DTR lines
+ */
+
+/*
+ *  ns16550_assert_RTS
+ */
+
+static void ns16550_assert_RTS(rtems_termios_device_context *base)
+{
+  ns16550_context             *ctx = (ns16550_context *) base;
+  rtems_interrupt_lock_context lock_context;
+
+  /*
+   * Assert RTS
+   */
+  rtems_termios_device_lock_acquire(base, &lock_context);
+  ctx->modem_control |= SP_MODEM_RTS;
+  (*ctx->set_reg)(ctx->port, NS16550_MODEM_CONTROL, ctx->modem_control);
+  rtems_termios_device_lock_release(base, &lock_context);
+}
+
+/*
+ *  ns16550_negate_RTS
+ */
+
+static void ns16550_negate_RTS(rtems_termios_device_context *base)
+{
+  ns16550_context             *ctx = (ns16550_context *) base;
+  rtems_interrupt_lock_context lock_context;
+
+  /*
+   * Negate RTS
+   */
+  rtems_termios_device_lock_acquire(base, &lock_context);
+  ctx->modem_control &= ~SP_MODEM_RTS;
+  (*ctx->set_reg)(ctx->port, NS16550_MODEM_CONTROL, ctx->modem_control);
+  rtems_termios_device_lock_release(base, &lock_context);
+}
+
+/*
+ * These flow control routines utilise a connection from the local DTR
+ * line to the remote CTS line
+ */
+
+/*
+ *  ns16550_assert_DTR
+ */
+
+static void ns16550_assert_DTR(rtems_termios_device_context *base)
+{
+  ns16550_context             *ctx = (ns16550_context *) base;
+  rtems_interrupt_lock_context lock_context;
+
+  /*
+   * Assert DTR
+   */
+  rtems_termios_device_lock_acquire(base, &lock_context);
+  ctx->modem_control |= SP_MODEM_DTR;
+  (*ctx->set_reg)(ctx->port, NS16550_MODEM_CONTROL, ctx->modem_control);
+  rtems_termios_device_lock_release(base, &lock_context);
+}
+
+/*
+ *  ns16550_negate_DTR
+ */
+
+static void ns16550_negate_DTR(rtems_termios_device_context *base)
+{
+  ns16550_context             *ctx = (ns16550_context *) base;
+  rtems_interrupt_lock_context lock_context;
+
+  /*
+   * Negate DTR
+   */
+  rtems_termios_device_lock_acquire(base, &lock_context);
+  ctx->modem_control &=~SP_MODEM_DTR;
+  (*ctx->set_reg)(ctx->port, NS16550_MODEM_CONTROL,ctx->modem_control);
+  rtems_termios_device_lock_release(base, &lock_context);
+}
+
+/*
+ *  ns16550_set_attributes
+ *
+ *  This function sets the channel to reflect the requested termios
+ *  port settings.
+ */
+
+static bool ns16550_set_attributes(
+  rtems_termios_device_context *base,
+  const struct termios         *t
+)
+{
+  ns16550_context        *ctx = (ns16550_context *) base;
+  uint32_t                pNS16550;
+  uint32_t                ulBaudDivisor;
+  uint8_t                 ucLineControl;
+  uint32_t                baud_requested;
+  ns16550_set_reg         setReg;
+
+  pNS16550 = ctx->port;
+  setReg   = ctx->set_reg;
+
+  /*
+   *  Calculate the baud rate divisor
+   *
+   *  Assert ensures there is no division by 0.
+   */
+
+  baud_requested = rtems_termios_baud_to_number(t->c_ospeed);
+  _Assert( baud_requested != 0 );
+
+  ulBaudDivisor = NS16550_GetBaudDivisor(ctx, baud_requested);
+
+  ucLineControl = 0;
+
+  /*
+   *  Parity
+   */
+
+  if (t->c_cflag & PARENB) {
+    ucLineControl |= SP_LINE_PAR;
+    if (!(t->c_cflag & PARODD))
+      ucLineControl |= SP_LINE_ODD;
+  }
+
+  /*
+   *  Character Size
+   */
+
+  if (t->c_cflag & CSIZE) {
+    switch (t->c_cflag & CSIZE) {
+      case CS5:  ucLineControl |= FIVE_BITS;  break;
+      case CS6:  ucLineControl |= SIX_BITS;   break;
+      case CS7:  ucLineControl |= SEVEN_BITS; break;
+      case CS8:  ucLineControl |= EIGHT_BITS; break;
+    }
+  } else {
+    ucLineControl |= EIGHT_BITS;               /* default to 9600,8,N,1 */
+  }
+
+  /*
+   *  Stop Bits
+   */
+
+  if (t->c_cflag & CSTOPB) {
+    ucLineControl |= SP_LINE_STOP;              /* 2 stop bits */
+  } else {
+    ;                                           /* 1 stop bit */
+  }
+
+  /*
+   *  Now actually set the chip
+   */
+
+  if (ulBaudDivisor != ctx->baud_divisor || ucLineControl != ctx->line_control) {
+    rtems_interrupt_lock_context lock_context;
+
+    ctx->baud_divisor = ulBaudDivisor;
+    ctx->line_control = ucLineControl;
+
+    rtems_termios_device_lock_acquire(base, &lock_context);
+
+    /*
+     *  Set the baud rate
+     *
+     *  NOTE: When the Divisor Latch Access Bit (DLAB) is set to 1,
+     *        the transmit buffer and interrupt enable registers
+     *        turn into the LSB and MSB divisor latch registers.
+     */
+
+    (*setReg)(pNS16550, NS16550_LINE_CONTROL, SP_LINE_DLAB);
+    (*setReg)(pNS16550, NS16550_TRANSMIT_BUFFER, ulBaudDivisor&0xff);
+    (*setReg)(pNS16550, NS16550_INTERRUPT_ENABLE, (ulBaudDivisor>>8)&0xff);
+
+    /*
+     *  Now write the line control
+     */
+    (*setReg)(pNS16550, NS16550_LINE_CONTROL, ucLineControl );
+
+    rtems_termios_device_lock_release(base, &lock_context);
+  }
+
+  return true;
+}
+
+/**
+ * @brief Transmits up to @a len characters from @a buf.
+ *
+ * This routine is invoked either from task context with disabled interrupts to
+ * start a new transmission process with exactly one character in case of an
+ * idle output state or from the interrupt handler to refill the transmitter.
+ *
+ * Returns always zero.
+ */
+static void ns16550_write_support_int(
+  rtems_termios_device_context *base,
+  const char                   *buf,
+  size_t                        len
+)
+{
+  ns16550_context *ctx = (ns16550_context *) base;
+
+  ctx->out_total = len;
+
+  if (len > 0) {
+    ctx->out_remaining = len;
+    ctx->out_buf = buf;
+    ctx->out_current = ns16550_write_to_fifo(ctx, buf, len);
+
+    ns16550_enable_interrupts(ctx, NS16550_ENABLE_ALL_INTR);
+  } else {
+    ns16550_enable_interrupts(ctx, NS16550_ENABLE_ALL_INTR_EXCEPT_TX);
+  }
+}
+
+static void ns16550_write_support_task(
+  rtems_termios_device_context *base,
+  const char                   *buf,
+  size_t                        len
+)
+{
+  ns16550_context *ctx = (ns16550_context *) base;
+
+  ctx->out_total = len;
+
+  if (len > 0) {
+    ctx->out_remaining = len;
+    ctx->out_buf = buf;
+    ctx->out_current = ns16550_write_to_fifo(ctx, buf, len);
+
+    ns16550_clear_and_set_interrupts(ctx, 0, SP_INT_TX_ENABLE);
+  }
+}
+
+/*
+ *  ns16550_write_support_polled
+ *
+ *  Console Termios output entry point.
+ *
+ */
+
+static void ns16550_write_support_polled(
+  rtems_termios_device_context *base,
+  const char                   *buf,
+  size_t                        len
+)
+{
+  size_t nwrite = 0;
+
+  /*
+   * poll each byte in the string out of the port.
+   */
+  while (nwrite < len) {
+    /*
+     * transmit character
+     */
+    ns16550_polled_putchar(base, *buf++);
+    nwrite++;
+  }
+}
+
+/*
+ *  Debug gets() support
+ */
+int ns16550_polled_getchar(rtems_termios_device_context *base)
+{
+  ns16550_context     *ctx = (ns16550_context *) base;
+  uint32_t             pNS16550;
+  unsigned char        ucLineStatus;
+  uint8_t              cChar;
+  ns16550_get_reg      getReg;
+
+  pNS16550 = ctx->port;
+  getReg   = ctx->get_reg;
+
+  ucLineStatus = (*getReg)(pNS16550, NS16550_LINE_STATUS);
+  if (ucLineStatus & SP_LSR_RDY) {
+    cChar = (*getReg)(pNS16550, NS16550_RECEIVE_BUFFER);
+    return (int)cChar;
+  }
+  return -1;
+}
+
+/*
+ * Flow control is only supported when using interrupts
+ */
+
+const rtems_termios_device_flow ns16550_flow_rtscts = {
+  .stop_remote_tx = ns16550_negate_RTS,
+  .start_remote_tx = ns16550_assert_RTS
+};
+
+const rtems_termios_device_flow ns16550_flow_dtrcts = {
+  .stop_remote_tx = ns16550_negate_DTR,
+  .start_remote_tx = ns16550_assert_DTR
+};
+
+const rtems_termios_device_handler ns16550_handler_interrupt = {
+  .first_open = ns16550_open,
+  .last_close = ns16550_close,
+  .poll_read = NULL,
+  .write = ns16550_write_support_int,
+  .set_attributes = ns16550_set_attributes,
+  .mode = TERMIOS_IRQ_DRIVEN
+};
+
+const rtems_termios_device_handler ns16550_handler_polled = {
+  .first_open = ns16550_open,
+  .last_close = ns16550_close,
+  .poll_read = ns16550_polled_getchar,
+  .write = ns16550_write_support_polled,
+  .set_attributes = ns16550_set_attributes,
+  .mode = TERMIOS_POLLED
+};
+
+const rtems_termios_device_handler ns16550_handler_task = {
+  .first_open = ns16550_open,
+  .last_close = ns16550_close,
+  .poll_read = ns16550_read_task,
+  .write = ns16550_write_support_task,
+  .set_attributes = ns16550_set_attributes,
+  .mode = TERMIOS_TASK_DRIVEN
+};