LXR uboot/drivers/serial/serial

   1/*
   2 * Copyright (C) 2013 Synopsys, Inc. (www.synopsys.com)
   3 *
   4 * This program is free software; you can redistribute it and/or modify
   5 * it under the terms of the GNU General Public License version 2 as
   6 * published by the Free Software Foundation.
   7 *
   8 */
   9
  10#include <common.h>
  11#include <serial.h>
  12
  13DECLARE_GLOBAL_DATA_PTR;
  14
  15struct arc_serial_regs {
  16        unsigned int id0;
  17        unsigned int id1;
  18        unsigned int id2;
  19        unsigned int id3;
  20        unsigned int data;
  21        unsigned int status;
  22        unsigned int baudl;
  23        unsigned int baudh;
  24};
  25
  26/* Bit definitions of STATUS register */
  27#define UART_RXEMPTY            (1 << 5)
  28#define UART_OVERFLOW_ERR       (1 << 1)
  29#define UART_TXEMPTY            (1 << 7)
  30
  31struct arc_serial_regs *regs;
  32
  33static void arc_serial_setbrg(void)
  34{
  35        int arc_console_baud;
  36
  37        if (!gd->baudrate)
  38                gd->baudrate = CONFIG_BAUDRATE;
  39
  40        arc_console_baud = gd->cpu_clk / (gd->baudrate * 4) - 1;
  41        writeb(arc_console_baud & 0xff, &regs->baudl);
  42
  43#ifdef CONFIG_ARC
  44        /*
  45         * UART ISS(Instruction Set simulator) emulation has a subtle bug:
  46         * A existing value of Baudh = 0 is used as a indication to startup
  47         * it's internal state machine.
  48         * Thus if baudh is set to 0, 2 times, it chokes.
  49         * This happens with BAUD=115200 and the formaula above
  50         * Until that is fixed, when running on ISS, we will set baudh to !0
  51         */
  52        if (gd->arch.running_on_hw)
  53                writeb((arc_console_baud & 0xff00) >> 8, &regs->baudh);
  54        else
  55                writeb(1, &regs->baudh);
  56#else
  57        writeb((arc_console_baud & 0xff00) >> 8, &regs->baudh);
  58#endif
  59}
  60
  61static int arc_serial_init(void)
  62{
  63        regs = (struct arc_serial_regs *)CONFIG_ARC_UART_BASE;
  64        serial_setbrg();
  65        return 0;
  66}
  67
  68static void arc_serial_putc(const char c)
  69{
  70        if (c == '\n')
  71                arc_serial_putc('\r');
  72
  73        while (!(readb(&regs->status) & UART_TXEMPTY))
  74                ;
  75
  76        writeb(c, &regs->data);
  77}
  78
  79static int arc_serial_tstc(void)
  80{
  81        return !(readb(&regs->status) & UART_RXEMPTY);
  82}
  83
  84static int arc_serial_getc(void)
  85{
  86        while (!arc_serial_tstc())
  87                ;
  88
  89        /* Check for overflow errors */
  90        if (readb(&regs->status) & UART_OVERFLOW_ERR)
  91                return 0;
  92
  93        return readb(&regs->data) & 0xFF;
  94}
  95
  96static struct serial_device arc_serial_drv = {
  97        .name   = "arc_serial",
  98        .start  = arc_serial_init,
  99        .stop   = NULL,
 100        .setbrg = arc_serial_setbrg,
 101        .putc   = arc_serial_putc,
 102        .puts   = default_serial_puts,
 103        .getc   = arc_serial_getc,
 104        .tstc   = arc_serial_tstc,
 105};
 106
 107void arc_serial_initialize(void)
 108{
 109        serial_register(&arc_serial_drv);
 110}
 111
 112__weak struct serial_device *default_serial_console(void)
 113{
 114        return &arc_serial_drv;
 115}
 116