FreeBSD/Linux Kernel Cross Reference
sys/pexpert/i386/pe_serial.c

     /*
      * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
      *
      * @APPLE_LICENSE_HEADER_START@
      * 
      * The contents of this file constitute Original Code as defined in and
      * are subject to the Apple Public Source License Version 1.1 (the
      * "License").  You may not use this file except in compliance with the
      * License.  Please obtain a copy of the License at
     * http://www.apple.com/publicsource and read it before using this file.
     * 
     * This Original Code and all software distributed under the License are
     * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
     * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
     * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
     * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
     * License for the specific language governing rights and limitations
     * under the License.
     * 
     * @APPLE_LICENSE_HEADER_END@
     */
    
    /*
     * file: pe_serial.c
     *       Polled-mode 16x50 UART driver.
     */
    
    #include <pexpert/protos.h>
    #include <pexpert/pexpert.h>
    
    void    serial_putc(char);
    int     serial_getc(void);
    int     serial_init(void);
    
    /* standard port addresses */
    enum {
        COM1_PORT_ADDR = 0x3f8,
        COM2_PORT_ADDR = 0x2f8
    };
    
    /* UART register offsets */
    enum {
        UART_RBR = 0,  /* receive buffer Register   (R) */
        UART_THR = 0,  /* transmit holding register (W) */
        UART_DLL = 0,  /* DLAB = 1, divisor latch (LSB) */
        UART_IER = 1,  /* interrupt enable register     */
        UART_DLM = 1,  /* DLAB = 1, divisor latch (MSB) */
        UART_IIR = 2,  /* interrupt ident register (R)  */
        UART_FCR = 2,  /* fifo control register (W)     */
        UART_LCR = 3,  /* line control register         */
        UART_MCR = 4,  /* modem control register        */
        UART_LSR = 5,  /* line status register          */
        UART_MSR = 6   /* modem status register         */
    };
    
    enum {
        UART_LCR_8BITS = 0x03,
        UART_LCR_DLAB  = 0x80
    };
    
    enum {
        UART_MCR_DTR   = 0x01,
        UART_MCR_RTS   = 0x02,
        UART_MCR_OUT1  = 0x04,
        UART_MCR_OUT2  = 0x08,
        UART_MCR_LOOP  = 0x10
    };
    
    enum {
        UART_LSR_THRE  = 0x20
    };
    
    #define UART_BAUD_RATE  115200
    #define UART_PORT_ADDR  COM1_PORT_ADDR
    
    #define WRITE(r, v)  outb(UART_PORT_ADDR + UART_##r, v)
    #define READ(r)      inb(UART_PORT_ADDR + UART_##r)
    #define DELAY(x)     { volatile int _d_; for (_d_ = 0; _d_ < (10000*x); _d_++) ; }
    
    static int uart_initted = 0;   /* 1 if init'ed */
    
    static int
    uart_probe( void )
    {
        /* Verify that the Divisor Register is accessible */
    
        WRITE( LCR, UART_LCR_DLAB );
        WRITE( DLL, 0x5a );
        if (READ(DLL) != 0x5a) return 0;
        WRITE( DLL, 0xa5 );
        if (READ(DLL) != 0xa5) return 0;
        WRITE( LCR, 0x00 );
        return 1;
    }
    
    static void
    uart_set_baud_rate( unsigned long baud_rate )
    {
        #define UART_CLOCK  1843200   /* 1.8432 MHz clock */
   
       const unsigned char lcr = READ( LCR );
       unsigned long       div;
   
       if (baud_rate == 0) baud_rate = 9600;
       div = UART_CLOCK / 16 / baud_rate;
       WRITE( LCR, lcr | UART_LCR_DLAB );
       WRITE( DLM, (unsigned char)(div >> 8) );
       WRITE( DLL, (unsigned char) div );
       WRITE( LCR, lcr & ~UART_LCR_DLAB);
   }
   
   static void
   uart_putc( char c )
   {
       if (!uart_initted) return;
   
       /* Wait for THR empty */
       while ( !(READ(LSR) & UART_LSR_THRE) ) DELAY(1);
   
       WRITE( THR, c );
   }
   
   int serial_init( void )
   {
       if ( /*uart_initted ||*/ uart_probe() == 0 ) return 0;
   
       /* Disable hardware interrupts */
   
       WRITE( MCR, 0 );
       WRITE( IER, 0 );
   
       /* Disable FIFO's for 16550 devices */
   
       WRITE( FCR, 0 );
   
       /* Set for 8-bit, no parity, DLAB bit cleared */
   
       WRITE( LCR, UART_LCR_8BITS );
   
       /* Set baud rate */
   
       uart_set_baud_rate( UART_BAUD_RATE );
   
       /* Assert DTR# and RTS# lines (OUT2?) */
   
       WRITE( MCR, UART_MCR_DTR | UART_MCR_RTS );
   
       /* Clear any garbage in the input buffer */
   
       READ( RBR );
   
       uart_initted = 1;
   
       return 1;
   }
   
   void serial_putc( char c )
   {
       uart_putc(c);
       if (c == '\n') uart_putc('\r');
   }
   
   int serial_getc( void )
   {
       return 0;  /* not supported */
   }

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