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gdb-io-serial.c

/* 16550 serial driver for gdbstub I/O
 *
 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/console.h>
#include <linux/init.h>
#include <linux/nmi.h>

#include <asm/pgtable.h>
#include <asm/system.h>
#include <asm/gdb-stub.h>
#include <asm/exceptions.h>
#include <asm/serial-regs.h>
#include <asm/unit/serial.h>

/*
 * initialise the GDB stub
 */
void gdbstub_io_init(void)
{
      u16 tmp;

      /* set up the serial port */
      GDBPORT_SERIAL_LCR = UART_LCR_WLEN8; /* 1N8 */
      GDBPORT_SERIAL_FCR = (UART_FCR_ENABLE_FIFO | UART_FCR_CLEAR_RCVR |
                        UART_FCR_CLEAR_XMIT);

      FLOWCTL_CLEAR(DTR);
      FLOWCTL_SET(RTS);

      gdbstub_io_set_baud(115200);

      /* we want to get serial receive interrupts */
      XIRQxICR(GDBPORT_SERIAL_IRQ) = 0;
      tmp = XIRQxICR(GDBPORT_SERIAL_IRQ);

      IVAR0 = EXCEP_IRQ_LEVEL0;
      set_intr_stub(EXCEP_IRQ_LEVEL0, gdbstub_io_rx_handler);

      XIRQxICR(GDBPORT_SERIAL_IRQ) &= ~GxICR_REQUEST;
      XIRQxICR(GDBPORT_SERIAL_IRQ) = GxICR_ENABLE | GxICR_LEVEL_0;
      tmp = XIRQxICR(GDBPORT_SERIAL_IRQ);

      GDBPORT_SERIAL_IER = UART_IER_RDI | UART_IER_RLSI;

      /* permit level 0 IRQs to take place */
      asm volatile(
            "     and %0,epsw \n"
            "     or %1,epsw  \n"
            :
            : "i"(~EPSW_IM), "i"(EPSW_IE | EPSW_IM_1)
            );
}

/*
 * set up the GDB stub serial port baud rate timers
 */
void gdbstub_io_set_baud(unsigned baud)
{
      unsigned value;
      u8 lcr;

      value = 18432000 / 16 / baud;

      lcr = GDBPORT_SERIAL_LCR;
      GDBPORT_SERIAL_LCR |= UART_LCR_DLAB;
      GDBPORT_SERIAL_DLL = value & 0xff;
      GDBPORT_SERIAL_DLM = (value >> 8) & 0xff;
      GDBPORT_SERIAL_LCR = lcr;
}

/*
 * wait for a character to come from the debugger
 */
int gdbstub_io_rx_char(unsigned char *_ch, int nonblock)
{
      unsigned ix;
      u8 ch, st;

      *_ch = 0xff;

      if (gdbstub_rx_unget) {
            *_ch = gdbstub_rx_unget;
            gdbstub_rx_unget = 0;
            return 0;
      }

 try_again:
      /* pull chars out of the buffer */
      ix = gdbstub_rx_outp;
      barrier();
      if (ix == gdbstub_rx_inp) {
            if (nonblock)
                  return -EAGAIN;
#ifdef CONFIG_MN10300_WD_TIMER
            watchdog_alert_counter = 0;
#endif /* CONFIG_MN10300_WD_TIMER */
            goto try_again;
      }

      ch = gdbstub_rx_buffer[ix++];
      st = gdbstub_rx_buffer[ix++];
      barrier();
      gdbstub_rx_outp = ix & 0x00000fff;

      if (st & UART_LSR_BI) {
            gdbstub_proto("### GDB Rx Break Detected ###\n");
            return -EINTR;
      } else if (st & (UART_LSR_FE | UART_LSR_OE | UART_LSR_PE)) {
            gdbstub_proto("### GDB Rx Error (st=%02x) ###\n", st);
            return -EIO;
      } else {
            gdbstub_proto("### GDB Rx %02x (st=%02x) ###\n", ch, st);
            *_ch = ch & 0x7f;
            return 0;
      }
}

/*
 * send a character to the debugger
 */
void gdbstub_io_tx_char(unsigned char ch)
{
      FLOWCTL_SET(DTR);
      LSR_WAIT_FOR(THRE);
      /* FLOWCTL_WAIT_FOR(CTS); */

      if (ch == 0x0a) {
            GDBPORT_SERIAL_TX = 0x0d;
            LSR_WAIT_FOR(THRE);
            /* FLOWCTL_WAIT_FOR(CTS); */
      }
      GDBPORT_SERIAL_TX = ch;

      FLOWCTL_CLEAR(DTR);
}

/*
 * send a character to the debugger
 */
void gdbstub_io_tx_flush(void)
{
      LSR_WAIT_FOR(TEMT);
      LSR_WAIT_FOR(THRE);
      FLOWCTL_CLEAR(DTR);
}

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