drivers/serial/serial_arc.c

   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
  13 DECLARE_GLOBAL_DATA_PTR;
  14
  15 struct 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
  31 struct arc_serial_regs *regs;
  32
  33 static 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
  61 static int arc_serial_init(void)
  62 {
  63         regs = (struct arc_serial_regs *)CONFIG_ARC_UART_BASE;
  64         serial_setbrg();
  65         return 0;
  66 }
  67
  68 static 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
  79 static int arc_serial_tstc(void)
  80 {
  81         return !(readb(&regs->status) & UART_RXEMPTY);
  82 }
  83
  84 static 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
  96 static void arc_serial_puts(const char *s)
  97 {
  98         while (*s)
  99                 arc_serial_putc(*s++);
 100 }
 101
 102 static struct serial_device arc_serial_drv = {
 103         .name   = "arc_serial",
 104         .start  = arc_serial_init,
 105         .stop   = NULL,
 106         .setbrg = arc_serial_setbrg,
 107         .putc   = arc_serial_putc,
 108         .puts   = arc_serial_puts,
 109         .getc   = arc_serial_getc,
 110         .tstc   = arc_serial_tstc,
 111 };
 112
 113 void arc_serial_initialize(void)
 114 {
 115         serial_register(&arc_serial_drv);
 116 }
 117
 118 __weak struct serial_device *default_serial_console(void)
 119 {
 120         return &arc_serial_drv;
 121 }