From 1873780194ed34a0c8c71a09671938e6e2468afd Mon Sep 17 00:00:00 2001 From: Ben Pfaff Date: Tue, 7 Sep 2004 06:23:02 +0000 Subject: [PATCH] First stab at interrupt-driven serial. Receive doesn't work. --- src/devices/serial.c | 246 ++++++++++++++++++++++++++++++++++++++-- src/devices/serial.h | 5 +- src/lib/kernel/printf.c | 8 +- src/threads/init.c | 6 +- 4 files changed, 252 insertions(+), 13 deletions(-) diff --git a/src/devices/serial.c b/src/devices/serial.c index 41b52f6..1cb5bf6 100644 --- a/src/devices/serial.c +++ b/src/devices/serial.c @@ -3,28 +3,115 @@ #include "devices/16550a.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 + +#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; static void set_serial (int bps, int bits, enum parity_type parity, int stop); +static void update_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. */ void -serial_init (void) +serial_init (int level) { - 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. */ + 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 (); + } } +static void putc_busy_wait (uint8_t); +static void putc_queue (uint8_t); + /* Sends BYTE to the serial port. */ void -serial_outb (uint8_t byte) +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); + + queue_putc (&xmit_queue, byte); + update_ier (); + + queue_unlock (&xmit_queue); +} + +/* Reads and returns a byte from the serial port. */ +uint8_t +serial_getc (void) +{ + uint8_t byte; + queue_lock (&recv_queue); + + /* Read a byte. */ + byte = queue_getc (&recv_queue); + update_ier (); + + queue_unlock (&recv_queue); + return byte; +} + /* Configures the first serial port for BPS bits per second, BITS bits per byte, the given PARITY, and STOP stop bits. */ static void @@ -32,7 +119,7 @@ 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 +130,148 @@ 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. + 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 (); +} + +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); + +static void +queue_init (struct queue *q, const char *name) +{ + lock_init (&q->lock, name); + q->not_full = q->not_empty = NULL; + q->head = q->tail = 0; +} + +static void +queue_lock (struct queue *q) +{ + lock_acquire (&q->lock); + q->old_level = intr_disable (); +} + +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) +{ + 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 (); +} + +static void +signal (struct queue *q, struct thread **waiter) +{ + ASSERT (owned_by_current_thread (q)); + + if (*waiter != NULL) + { + thread_unblock (*waiter); + *waiter = NULL; + } +} diff --git a/src/devices/serial.h b/src/devices/serial.h index 672f8de..3ef124b 100644 --- a/src/devices/serial.h +++ b/src/devices/serial.h @@ -3,7 +3,8 @@ #include -void serial_init (void); -void serial_outb (uint8_t); +void serial_init (int phase); +void serial_putc (uint8_t); +uint8_t serial_getc (void); #endif /* devices/serial.h */ diff --git a/src/lib/kernel/printf.c b/src/lib/kernel/printf.c index 886706c..c139966 100644 --- a/src/lib/kernel/printf.c +++ b/src/lib/kernel/printf.c @@ -1,12 +1,14 @@ #include #include - #include "devices/serial.h" #include "devices/vga.h" #include "threads/interrupt.h" static void vprintf_helper (char, void *); +/* The standard vprintf() function, + which is like printf() but uses a va_list. + Writes its output to both vga display and serial port. */ int vprintf (const char *format, va_list args) { @@ -29,11 +31,11 @@ vprintf_helper (char c, void *char_cnt_) putchar (c); } -/* Writes C to the console. */ +/* Writes C to the vga display and serial port. */ int putchar (int c) { - serial_outb (c); + serial_putc (c); vga_putc (c); return c; } diff --git a/src/threads/init.c b/src/threads/init.c index d322764..2684d17 100644 --- a/src/threads/init.c +++ b/src/threads/init.c @@ -55,7 +55,7 @@ main (void) /* Needed by printf(), so initialize them very early. */ ram_init (); vga_init (); - serial_init (); + serial_init (1); /* Greet user. */ printf ("Booting cnachos86 with %'d kB RAM...\n", ram_pages * 4); @@ -87,6 +87,7 @@ main (void) /* Start thread scheduler and enable interrupts. */ thread_start (); + serial_init (2); #ifdef FILESYS /* Initialize filesystem. */ @@ -96,6 +97,9 @@ main (void) #endif printf ("Boot complete.\n"); + + for (;;) + putchar (serial_getc ()); #ifdef USERPROG /* Run a user program. */ -- 2.30.2