1 #include "devices/serial.h"
3 #include "devices/16550a.h"
4 #include "devices/intq.h"
5 #include "devices/timer.h"
6 #include "threads/io.h"
7 #include "threads/interrupt.h"
8 #include "threads/synch.h"
9 #include "threads/thread.h"
11 /* Transmission mode. */
12 static enum { UNINIT, POLL, QUEUE } mode;
14 /* Data to be transmitted. */
15 static struct intq txq;
17 static void set_serial (int bps, int bits, enum parity_type parity, int stop);
18 static void putc_poll (uint8_t);
19 static void write_ier (void);
20 static intr_handler_func serial_interrupt;
22 /* Initializes the serial port device for polling mode.
23 Polling mode busy-waits for the serial port to become free
24 before writing to it. It's slow, but until interrupts have
25 been initialized it's all we can do. */
27 serial_init_poll (void)
29 ASSERT (mode == UNINIT);
30 outb (IER_REG, 0); /* Turn off all interrupts. */
31 outb (FCR_REG, 0); /* Disable FIFO. */
32 set_serial (9600, 8, NONE, 1); /* 9600 bps, N-8-1. */
33 outb (MCR_REG, 8); /* Turn on OUT2 output line. */
34 intq_init (&txq, "serial xmit");
38 /* Initializes the serial port device for queued interrupt-driven
39 I/O. With interrupt-driven I/O we don't waste CPU time
40 waiting for the serial device to become ready. */
42 serial_init_queue (void)
44 ASSERT (mode == POLL);
45 intr_register (0x20 + 4, 0, INTR_OFF, serial_interrupt, "serial");
49 /* Sends BYTE to the serial port. */
51 serial_putc (uint8_t byte)
53 enum intr_level old_level = intr_disable ();
55 if (mode == POLL || old_level == INTR_OFF)
57 /* If we're not set up for interrupt-driven I/O yet,
58 or if interrupts are off,
59 use dumb polling for serial I/O. */
65 /* Otherwise, queue a byte and update the interrupt enable
67 intq_putc (&txq, byte);
71 intr_set_level (old_level);
74 /* Flushes anything in the serial buffer out the port in polling
79 enum intr_level old_level = intr_disable ();
80 while (!intq_empty (&txq))
81 putc_poll (intq_getc (&txq));
82 intr_set_level (old_level);
85 /* Configures the serial port for BPS bits per second, BITS bits
86 per byte, the given PARITY, and STOP stop bits. */
88 set_serial (int bps, int bits, enum parity_type parity, int stop)
90 int baud_base = 1843200 / 16; /* Base rate of 16550A. */
91 uint16_t divisor = baud_base / bps; /* Clock rate divisor. */
94 outb (LCR_REG, make_lcr (bits, parity, stop, false, true));
97 outb (LS_REG, divisor & 0xff);
98 outb (MS_REG, divisor >> 8);
101 outb (LCR_REG, make_lcr (bits, parity, stop, false, false));
104 /* Update interrupt enable register.
105 If our transmit queue is empty, turn off transmit interrupt. */
109 outb (IER_REG, intq_empty (&txq) ? 0 : IER_XMIT);
113 /* Polls the serial port until it's ready,
114 and then transmits BYTE. */
116 putc_poll (uint8_t byte)
118 ASSERT (intr_get_level () == INTR_OFF);
120 while ((inb (LSR_REG) & LSR_THRE) == 0)
122 outb (THR_REG, byte);
125 /* Serial interrupt handler.
126 As long as we have a byte to transmit,
127 and the hardware is ready to accept a byte for transmission,
129 Then update interrupt enable register based on queue
132 serial_interrupt (struct intr_frame *f UNUSED)
134 while (!intq_empty (&txq) && (inb (LSR_REG) & LSR_THRE) != 0)
135 outb (THR_REG, intq_getc (&txq));