diff options
Diffstat (limited to 'com32/gdbstub/serial.c')
| -rw-r--r-- | com32/gdbstub/serial.c | 190 |
1 files changed, 190 insertions, 0 deletions
diff --git a/com32/gdbstub/serial.c b/com32/gdbstub/serial.c new file mode 100644 index 00000000..1c4d4b6f --- /dev/null +++ b/com32/gdbstub/serial.c @@ -0,0 +1,190 @@ +/* + * The serial port interface routines implement a simple polled i/o + * interface to a standard serial port. Due to the space restrictions + * for the boot blocks, no BIOS support is used (since BIOS requires + * expensive real/protected mode switches), instead the rudimentary + * BIOS support is duplicated here. + * + * The base address and speed for the i/o port are passed from the + * Makefile in the COMCONSOLE and CONSPEED preprocessor macros. The + * line control parameters are currently hard-coded to 8 bits, no + * parity, 1 stop bit (8N1). This can be changed in init_serial(). + */ + +#include <stddef.h> +#include <sys/io.h> +#include "serial.h" + +/* Set default values if none specified */ + +#ifndef COMCONSOLE +#define COMCONSOLE 0x3f8 +#endif + +#ifndef COMSPEED +#define COMSPEED 9600 +#endif + +#ifndef COMDATA +#define COMDATA 8 +#endif + +#ifndef COMPARITY +#define COMPARITY 0 +#endif + +#ifndef COMSTOP +#define COMSTOP 1 +#endif + +#undef UART_BASE +#define UART_BASE ( COMCONSOLE ) + +#undef UART_BAUD +#define UART_BAUD ( COMSPEED ) + +#if ((115200%UART_BAUD) != 0) +#error Bad ttys0 baud rate +#endif + +#define COMBRD (115200/UART_BAUD) + +/* Line Control Settings */ +#define UART_LCS ( ( ( (COMDATA) - 5 ) << 0 ) | \ + ( ( (COMPARITY) ) << 3 ) | \ + ( ( (COMSTOP) - 1 ) << 2 ) ) + +/* Data */ +#define UART_RBR 0x00 +#define UART_TBR 0x00 + +/* Control */ +#define UART_IER 0x01 +#define UART_IIR 0x02 +#define UART_FCR 0x02 +#define UART_LCR 0x03 +#define UART_MCR 0x04 +#define UART_DLL 0x00 +#define UART_DLM 0x01 + +/* Status */ +#define UART_LSR 0x05 +#define UART_LSR_TEMPT 0x40 /* Transmitter empty */ +#define UART_LSR_THRE 0x20 /* Transmit-hold-register empty */ +#define UART_LSR_BI 0x10 /* Break interrupt indicator */ +#define UART_LSR_FE 0x08 /* Frame error indicator */ +#define UART_LSR_PE 0x04 /* Parity error indicator */ +#define UART_LSR_OE 0x02 /* Overrun error indicator */ +#define UART_LSR_DR 0x01 /* Receiver data ready */ + +#define UART_MSR 0x06 +#define UART_SCR 0x07 + +#define uart_readb(addr) inb(addr) +#define uart_writeb(val,addr) outb((val),(addr)) + +/* + * void serial_putc(int ch); + * Write character `ch' to port UART_BASE. + */ +void serial_putc ( int ch ) { + int status; + for (;;) { + status = uart_readb(UART_BASE + UART_LSR); + if (status & UART_LSR_THRE) { + /* TX buffer emtpy */ + uart_writeb(ch, UART_BASE + UART_TBR); + break; + } + } +} + +/* + * int serial_getc(void); + * Read a character from port UART_BASE. + */ +int serial_getc ( void ) { + int status; + int ch; + do { + status = uart_readb(UART_BASE + UART_LSR); + } while((status & 1) == 0); + ch = uart_readb(UART_BASE + UART_RBR); /* fetch (first) character */ + ch &= 0x7f; /* remove any parity bits we get */ + if (ch == 0x7f) { /* Make DEL... look like BS */ + ch = 0x08; + } + return ch; +} + +/* + * int serial_init(void); + * Initialize port UART_BASE to speed COMSPEED, line settings 8N1. + */ +void serial_init ( void ) { + int status; + int divisor, lcs; + + divisor = COMBRD; + lcs = UART_LCS; + + +#ifdef COMPRESERVE + lcs = uart_readb(UART_BASE + UART_LCR) & 0x7f; + uart_writeb(0x80 | lcs, UART_BASE + UART_LCR); + divisor = (uart_readb(UART_BASE + UART_DLM) << 8) | uart_readb(UART_BASE + UART_DLL); + uart_writeb(lcs, UART_BASE + UART_LCR); +#endif + + /* Set Baud Rate Divisor to COMSPEED, and test to see if the + * serial port appears to be present. + */ + uart_writeb(0x80 | lcs, UART_BASE + UART_LCR); + uart_writeb(0xaa, UART_BASE + UART_DLL); + if (uart_readb(UART_BASE + UART_DLL) != 0xaa) { + goto out; + } + uart_writeb(0x55, UART_BASE + UART_DLL); + if (uart_readb(UART_BASE + UART_DLL) != 0x55) { + goto out; + } + uart_writeb(divisor & 0xff, UART_BASE + UART_DLL); + if (uart_readb(UART_BASE + UART_DLL) != (divisor & 0xff)) { + goto out; + } + uart_writeb(0xaa, UART_BASE + UART_DLM); + if (uart_readb(UART_BASE + UART_DLM) != 0xaa) { + goto out; + } + uart_writeb(0x55, UART_BASE + UART_DLM); + if (uart_readb(UART_BASE + UART_DLM) != 0x55) { + goto out; + } + uart_writeb((divisor >> 8) & 0xff, UART_BASE + UART_DLM); + if (uart_readb(UART_BASE + UART_DLM) != ((divisor >> 8) & 0xff)) { + goto out; + } + uart_writeb(lcs, UART_BASE + UART_LCR); + + /* disable interrupts */ + uart_writeb(0x0, UART_BASE + UART_IER); + + /* disable fifo's */ + uart_writeb(0x00, UART_BASE + UART_FCR); + + /* Set clear to send, so flow control works... */ + uart_writeb((1<<1), UART_BASE + UART_MCR); + + + /* Flush the input buffer. */ + do { + /* rx buffer reg + * throw away (unconditionally the first time) + */ + (void) uart_readb(UART_BASE + UART_RBR); + /* line status reg */ + status = uart_readb(UART_BASE + UART_LSR); + } while(status & UART_LSR_DR); + out: + return; +} |