X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Fdevices%2Fserial.c;h=64ce90f1b38df441526c4500c3e276c5ce604c40;hb=b2a1e970fa78d8b4c31239ff2ac9ef2b4bab09a7;hp=eeac40a165443e7c883022093a7d352627030126;hpb=f6580e9ad405b519dbe85027691bf3c66074b0a4;p=pintos-anon

diff --git a/src/devices/serial.c b/src/devices/serial.c
index eeac40a..64ce90f 100644
--- a/src/devices/serial.c
+++ b/src/devices/serial.c
@@ -1,38 +1,81 @@
-#include "serial.h"
-#include "16550a.h"
-#include "timer.h"
-#include "lib/debug.h"
+#include "devices/serial.h"
+#include <debug.h>
+#include "devices/16550a.h"
+#include "devices/intq.h"
+#include "devices/timer.h"
 #include "threads/io.h"
+#include "threads/interrupt.h"
+#include "threads/synch.h"
+#include "threads/thread.h"
+
+/* Transmission mode. */
+static enum { UNINIT, POLL, QUEUE } mode;
+
+/* Data to be transmitted. */
+static struct intq txq;
 
 static void set_serial (int bps, int bits, enum parity_type parity, int stop);
+static void write_ier (void);
+static intr_handler_func serial_interrupt;
 
-/* Initializes the serial port device. */
+/* Initializes the serial port device for polling mode.
+   Polling mode busy-waits for the serial port to become free
+   before writing to it.  It's slow, but until interrupts have
+   been initialized it's all we can do. */
 void
-serial_init (void) 
+serial_init_poll (void) 
 {
-  outb (IER_REG, 0);    /* Turn off all interrupts. */
-  outb (FCR_REG, 0);    /* Disable FIFO. */
-  set_serial (9600, 8, NONE, 1);
-  outb (MCR_REG, 0);    /* Turn off output lines. */
+  ASSERT (mode == UNINIT);
+  outb (IER_REG, 0);                    /* Turn off all interrupts. */
+  outb (FCR_REG, 0);                    /* Disable FIFO. */
+  set_serial (9600, 8, NONE, 1);        /* 9600 bps, N-8-1. */
+  outb (MCR_REG, 8);                    /* Turn on OUT2 output line. */
+  mode = POLL;
+} 
+
+/* Initializes the serial port device for queued interrupt-driven
+   I/O.  With interrupt-driven I/O we don't waste CPU time
+   waiting for the serial device to become ready. */
+void
+serial_init_queue (void) 
+{
+  ASSERT (mode == POLL);
+  intq_init (&txq, "serial xmit");
+  intr_register (0x20 + 4, 0, INTR_OFF, serial_interrupt, "serial");
+  mode = QUEUE;
 }
 
 /* Sends BYTE to the serial port. */
 void
-serial_outb (uint8_t byte) 
+serial_putc (uint8_t byte) 
 {
-  while ((inb (LSR_REG) & LSR_THRE) == 0)
-    continue;
-  outb (THR_REG, byte);
+  if (mode == POLL || intr_context ())
+    {
+      /* Poll the serial port until it's ready for a byte, and
+         then transmit. */
+      while ((inb (LSR_REG) & LSR_THRE) == 0)
+        continue;
+      outb (THR_REG, byte);
+    }
+  else
+    {
+      /* Lock the queue, add a byte, and update the interrupt
+         enable register. */
+      intq_lock (&txq);
+      intq_putc (&txq, byte); 
+      write_ier ();
+      intq_unlock (&txq);
+    }
 }
 
-/* Configures the first serial port for BPS bits per second,
-   BITS bits per byte, the given PARITY, and STOP stop bits. */
+/* Configures the serial port for BPS bits per second, BITS bits
+   per byte, the given PARITY, and STOP stop bits. */
 static void
 set_serial (int bps, int bits, enum parity_type parity, int stop)
 {
   int baud_base = 1843200 / 16;         /* Base rate of 16550A. */
   uint16_t divisor = baud_base / bps;   /* Clock rate divisor. */
-    
+
   /* Enable DLAB. */
   outb (LCR_REG, make_lcr (bits, parity, stop, false, true));
 
@@ -43,3 +86,25 @@ set_serial (int bps, int bits, enum parity_type parity, int stop)
   /* Reset DLAB. */
   outb (LCR_REG, make_lcr (bits, parity, stop, false, false));
 }
+
+/* Update interrupt enable register.
+   If our transmit queue is empty, turn off transmit interrupt. */
+static void
+write_ier (void) 
+{
+  outb (IER_REG, intq_empty (&txq) ? 0 : IER_XMIT);
+}
+
+/* Serial interrupt handler.
+   As long as we have a byte to transmit,
+   and the hardware is ready to accept a byte for transmission,
+   transmit a byte.
+   Then update interrupt enable register based on queue
+   status. */
+static void
+serial_interrupt (struct intr_frame *f UNUSED) 
+{
+  while (!intq_empty (&txq) && (inb (LSR_REG) & LSR_THRE) != 0) 
+    outb (THR_REG, intq_getc (&txq));
+  write_ier ();
+}