#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"
-#if 1
-#include "devices/vga.h"
-#endif
+/* Transmission mode. */
+static enum { UNINIT, POLL, QUEUE } mode;
-#define QUEUE_BUFSIZE 8
-
-struct queue
- {
- enum intr_level old_level;
- struct lock lock;
-
- struct thread *not_full, *not_empty;
- uint8_t buf[QUEUE_BUFSIZE];
- size_t head, tail;
- };
-
-static struct queue recv_queue, xmit_queue;
-static int init_level;
+/* Data to be transmitted. */
+static struct intq txq;
static void set_serial (int bps, int bits, enum parity_type parity, int stop);
-static void update_ier (void);
+static void putc_poll (uint8_t);
+static void write_ier (void);
static intr_handler_func serial_interrupt;
-static void queue_init (struct queue *, const char *);
-static void queue_lock (struct queue *);
-static void queue_unlock (struct queue *);
-static bool queue_empty (const struct queue *);
-static bool queue_full (const struct queue *);
-static uint8_t queue_getc (struct queue *);
-static void queue_putc (struct queue *, uint8_t);
-
-/* 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 (int level)
+serial_init_poll (void)
+{
+ 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. */
+ intq_init (&txq, "serial xmit");
+ 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)
{
- init_level = level;
- switch (level)
- {
- case 1:
- 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 off output lines. */
- break;
-
- case 2:
- /* Prepare interrupt handler. */
- queue_init (&recv_queue, "serial recv");
- queue_init (&xmit_queue, "serial xmit");
- intr_register (0x20 + 4, 0, INTR_OFF, serial_interrupt, "serial");
- outb (IER_REG, IER_RECV);
- break;
-
- default:
- NOT_REACHED ();
- }
+ ASSERT (mode == POLL);
+ intr_register (0x20 + 4, 0, INTR_OFF, serial_interrupt, "serial");
+ mode = QUEUE;
}
-static void putc_busy_wait (uint8_t);
-static void putc_queue (uint8_t);
-
/* Sends BYTE to the serial port. */
void
serial_putc (uint8_t byte)
{
- if (init_level == 1 || intr_context ())
- putc_busy_wait (byte);
- else
- putc_queue (byte);
-}
-
-static void
-putc_busy_wait (uint8_t byte)
-{
- while ((inb (LSR_REG) & LSR_THRE) == 0)
- continue;
- outb (THR_REG, byte);
-}
-
-static void
-putc_queue (uint8_t byte)
-{
- queue_lock (&xmit_queue);
+ enum intr_level old_level = intr_disable ();
- queue_putc (&xmit_queue, byte);
- update_ier ();
-
- queue_unlock (&xmit_queue);
+ if (mode == POLL || old_level == INTR_OFF)
+ {
+ /* If we're not set up for interrupt-driven I/O yet,
+ or if interrupts are off,
+ use dumb polling for serial I/O. */
+ serial_flush ();
+ putc_poll (byte);
+ }
+ else
+ {
+ /* Otherwise, queue a byte and update the interrupt enable
+ register. */
+ intq_putc (&txq, byte);
+ write_ier ();
+ }
+
+ intr_set_level (old_level);
}
-/* Reads and returns a byte from the serial port. */
-uint8_t
-serial_getc (void)
+/* Flushes anything in the serial buffer out the port in polling
+ mode. */
+void
+serial_flush (void)
{
- uint8_t byte;
- queue_lock (&recv_queue);
-
- /* Read a byte. */
- byte = queue_getc (&recv_queue);
- update_ier ();
-
- queue_unlock (&recv_queue);
- return byte;
+ enum intr_level old_level = intr_disable ();
+ while (!intq_empty (&txq))
+ putc_poll (intq_getc (&txq));
+ intr_set_level (old_level);
}
-/* 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)
{
}
/* Update interrupt enable register.
- If our transmit queue is empty, turn off transmit interrupt.
- If our receive queue is full, turn off receive interrupt. */
-static void
-update_ier (void)
-{
- uint8_t ier = 0;
-
- ASSERT (intr_get_level () == INTR_OFF);
-
- if (!queue_empty (&xmit_queue))
- ier |= IER_XMIT;
- if (!queue_full (&recv_queue))
- ier |= IER_RECV;
- outb (IER_REG, ier);
-}
-
-static void
-serial_interrupt (struct intr_frame *f UNUSED)
-{
- /* As long as the hardware is ready to take a byte
- and we have a byte to give it,
- transmit a byte. */
- while ((inb (LSR_REG) & LSR_THRE) != 0 && !queue_empty (&xmit_queue))
- outb (THR_REG, queue_getc (&xmit_queue));
-
- /* As long as the hardware has a byte to give us
- and we have space in our buffer for a byte,
- receive a byte. */
- while ((inb (LSR_REG) & LSR_DR) != 0 && !queue_full (&recv_queue))
- queue_putc (&recv_queue, inb (RBR_REG));
-
- /* Update interrupt enable register based on queue status. */
- update_ier ();
-}
-\f
-static size_t next (size_t pos);
-static bool owned_by_current_thread (const struct queue *);
-static void wait (struct queue *q, struct thread **waiter);
-static void signal (struct queue *q, struct thread **waiter);
-
+ If our transmit queue is empty, turn off transmit interrupt. */
static void
-queue_init (struct queue *q, const char *name)
+write_ier (void)
{
- lock_init (&q->lock, name);
- q->not_full = q->not_empty = NULL;
- q->head = q->tail = 0;
+ outb (IER_REG, intq_empty (&txq) ? 0 : IER_XMIT);
}
-static void
-queue_lock (struct queue *q)
-{
- lock_acquire (&q->lock);
- q->old_level = intr_disable ();
-}
+/* Polls the serial port until it's ready,
+ and then transmits BYTE. */
static void
-queue_unlock (struct queue *q)
-{
- ASSERT (!intr_context ());
- ASSERT (owned_by_current_thread (q));
-
- lock_release (&q->lock);
- intr_set_level (q->old_level);
-}
-
-static bool
-queue_empty (const struct queue *q)
+putc_poll (uint8_t byte)
{
ASSERT (intr_get_level () == INTR_OFF);
- return q->head == q->tail;
-}
-
-static bool
-queue_full (const struct queue *q)
-{
- ASSERT (intr_get_level () == INTR_OFF);
- return q->head == next (q->tail);
-}
-
-static uint8_t
-queue_getc (struct queue *q)
-{
- uint8_t byte;
-
- ASSERT (owned_by_current_thread (q));
- while (queue_empty (q))
- wait (q, &q->not_empty);
-
- byte = q->buf[q->head];
- q->head = next (q->head);
- signal (q, &q->not_full);
- return byte;
-}
-
-static void
-queue_putc (struct queue *q, uint8_t byte)
-{
- ASSERT (intr_get_level () == INTR_OFF);
-
- ASSERT (owned_by_current_thread (q));
- while (queue_full (q))
- wait (q, &q->not_full);
-
- q->buf[q->tail] = byte;
- q->tail = next (q->tail);
- signal (q, &q->not_empty);
-}
-
-static size_t
-next (size_t pos)
-{
- return (pos + 1) % QUEUE_BUFSIZE;
-}
-
-static bool
-owned_by_current_thread (const struct queue *q)
-{
- return (intr_context ()
- || (lock_held_by_current_thread (&q->lock)
- && intr_get_level () == INTR_OFF));
-}
-static void
-wait (struct queue *q, struct thread **waiter)
-{
- ASSERT (!intr_context ());
- ASSERT (owned_by_current_thread (q));
-
- *waiter = thread_current ();
- thread_block ();
+ while ((inb (LSR_REG) & LSR_THRE) == 0)
+ continue;
+ outb (THR_REG, byte);
}
+/* 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
-signal (struct queue *q, struct thread **waiter)
+serial_interrupt (struct intr_frame *f UNUSED)
{
- ASSERT (owned_by_current_thread (q));
-
- if (*waiter != NULL)
- {
- thread_unblock (*waiter);
- *waiter = NULL;
- }
+ while (!intq_empty (&txq) && (inb (LSR_REG) & LSR_THRE) != 0)
+ outb (THR_REG, intq_getc (&txq));
+ write_ier ();
}
projects / pintos-anon / blobdiff