[ashell] Fix for ashell boot (zephyrproject-rtos#1615)

Currently ashell boot doesn't work with javascript with callbacks
or timers.  This is because once the boot.cfg JS gets called, it
goes into an infinite loop waiting for uart. Until it gets the
connection, it won't return.  This means the main loop doesn't get
control back, meaning callbacks are not processed.  This breaks
the code up a bit so that it checks if the connection is ready
when uart_process gets called, if not try to connect.  If the
connection fails, just return and go through the main loop again.
Continue until a connection is made.

Fixes zephyrproject-rtos#1561

Signed-off-by: Brian J Jones <brian.j.jones@intel.com>

Author: brianjjones

src/ashell/term-uart.c

@@ -90,6 +90,7 @@ u32_t free_count = 0;
 static struct uart_input *isr_data = NULL;
 static u32_t tail = 0;
 static char *buf;
+static u32_t dtr = 0;
 
 struct uart_input *fifo_get_isr_buffer()
 {
@@ -316,7 +317,6 @@ static int uart_out(int c)
     return 1;
 }
 
-#ifdef CONFIG_UART_LINE_CTRL
 u32_t uart_get_baudrate(void)
 {
     u32_t baudrate;
@@ -329,13 +329,60 @@ u32_t uart_get_baudrate(void)
 
     return baudrate;
 }
-#endif
+
+static void uart_ready()
+{
+    // Need a short wait after uart_line_ctrl_get success
+    k_sleep(1000);
+
+    uart_irq_rx_disable(dev_upload);
+    uart_irq_tx_disable(dev_upload);
+
+    uart_irq_callback_set(dev_upload, uart_interrupt_handler);
+    terminal->send(banner, sizeof(banner));
+
+    /* Enable rx interrupts */
+    uart_irq_rx_enable(dev_upload);
+    DBG("[Listening]\n");
+
+    __stdout_hook_install(uart_out);
+
+    // Disable buffering on stdout since some parts write directly to uart fifo
+    setbuf(stdout, NULL);
+
+    ashell_help("");
+    comms_print(comms_get_prompt());
+    process_state = 0;
+
+    atomic_set(&uart_state, UART_INIT);
+
+    DBG("[Init]\n");
+    terminal->init();
+}
+
+static bool check_uart_connection()
+{
+    // Try to connect to the device
+    uart_line_ctrl_get(dev_upload, LINE_CTRL_DTR, &dtr);
+    if (dtr) {
+        uart_ready();
+        return true;
+    }
+    return false;
+}
 
 /*
  * Process user input
  */
 void uart_process()
 {
+    if (!dtr) {
+        if (!check_uart_connection()) {
+            // No connection yet, bail out
+            return;
+        }
+    }
+
     static struct uart_input *data = NULL;
     char *buf = NULL;
     u32_t len = 0;
@@ -416,47 +463,6 @@ void uart_init()
     k_fifo_init(&avail_queue);
 
     ashell_run_boot_cfg();
-
-#ifdef CONFIG_UART_LINE_CTRL
-    u32_t dtr = 0;
-
-    while (1) {
-        uart_line_ctrl_get(dev_upload, LINE_CTRL_DTR, &dtr);
-        if (dtr)
-            break;
-        // Sleep is needed to allow the javascript in boot.cfg to run
-        // while we wait for the connection.
-        k_sleep(1000);
-    }
-
-    /* 1000 msec = 1 sec */
-    k_sleep(1000);
-
-#endif
-
-    uart_irq_rx_disable(dev_upload);
-    uart_irq_tx_disable(dev_upload);
-
-    uart_irq_callback_set(dev_upload, uart_interrupt_handler);
-    terminal->send(banner, sizeof(banner));
-
-    /* Enable rx interrupts */
-    uart_irq_rx_enable(dev_upload);
-    DBG("[Listening]\n");
-
-    __stdout_hook_install(uart_out);
-
-    // Disable buffering on stdout since some parts write directly to uart fifo
-    setbuf(stdout, NULL);
-
-    ashell_help("");
-    comms_print(comms_get_prompt());
-    process_state = 0;
-
-    atomic_set(&uart_state, UART_INIT);
-
-    DBG("[Init]\n");
-    terminal->init();
 }
 
 void zjs_ashell_init()