drivers/serial/arm_dcc.c

   1 /*
   2  * Copyright (C) 2004-2007 ARM Limited.
   3  * Copyright (C) 2008 Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU General Public License version 2
   7  * as published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  17  *
  18  * As a special exception, if other files instantiate templates or use macros
  19  * or inline functions from this file, or you compile this file and link it
  20  * with other works to produce a work based on this file, this file does not
  21  * by itself cause the resulting work to be covered by the GNU General Public
  22  * License. However the source code for this file must still be made available
  23  * in accordance with section (3) of the GNU General Public License.
  24
  25  * This exception does not invalidate any other reasons why a work based on
  26  * this file might be covered by the GNU General Public License.
  27  */
  28
  29 #include <common.h>
  30 #include <serial.h>
  31
  32 #if defined(CONFIG_CPU_V6)
  33 /*
  34  * ARMV6
  35  */
  36 #define DCC_RBIT        (1 << 30)
  37 #define DCC_WBIT        (1 << 29)
  38
  39 #define write_dcc(x)    \
  40                 __asm__ volatile ("mcr p14, 0, %0, c0, c5, 0\n" : : "r" (x))
  41
  42 #define read_dcc(x)     \
  43                 __asm__ volatile ("mrc p14, 0, %0, c0, c5, 0\n" : "=r" (x))
  44
  45 #define status_dcc(x)   \
  46                 __asm__ volatile ("mrc p14, 0, %0, c0, c1, 0\n" : "=r" (x))
  47
  48 #elif defined(CONFIG_CPU_XSCALE)
  49 /*
  50  * XSCALE
  51  */
  52 #define DCC_RBIT        (1 << 31)
  53 #define DCC_WBIT        (1 << 28)
  54
  55 #define write_dcc(x)    \
  56                 __asm__ volatile ("mcr p14, 0, %0, c8, c0, 0\n" : : "r" (x))
  57
  58 #define read_dcc(x)     \
  59                 __asm__ volatile ("mrc p14, 0, %0, c9, c0, 0\n" : "=r" (x))
  60
  61 #define status_dcc(x)   \
  62                 __asm__ volatile ("mrc p14, 0, %0, c14, c0, 0\n" : "=r" (x))
  63
  64 #else
  65 #define DCC_RBIT        (1 << 0)
  66 #define DCC_WBIT        (1 << 1)
  67
  68 #define write_dcc(x)    \
  69                 __asm__ volatile ("mcr p14, 0, %0, c1, c0, 0\n" : : "r" (x))
  70
  71 #define read_dcc(x)     \
  72                 __asm__ volatile ("mrc p14, 0, %0, c1, c0, 0\n" : "=r" (x))
  73
  74 #define status_dcc(x)   \
  75                 __asm__ volatile ("mrc p14, 0, %0, c0, c0, 0\n" : "=r" (x))
  76
  77 #endif
  78
  79 #define can_read_dcc(x) do {    \
  80                 status_dcc(x);  \
  81                 x &= DCC_RBIT;  \
  82                 } while (0);
  83
  84 #define can_write_dcc(x) do {   \
  85                 status_dcc(x);  \
  86                 x &= DCC_WBIT;  \
  87                 x = (x == 0);   \
  88                 } while (0);
  89
  90 #define TIMEOUT_COUNT 0x4000000
  91
  92 static int arm_dcc_init(void)
  93 {
  94         return 0;
  95 }
  96
  97 static int arm_dcc_getc(void)
  98 {
  99         int ch;
 100         register unsigned int reg;
 101
 102         do {
 103                 can_read_dcc(reg);
 104         } while (!reg);
 105         read_dcc(ch);
 106
 107         return ch;
 108 }
 109
 110 static void arm_dcc_putc(char ch)
 111 {
 112         register unsigned int reg;
 113         unsigned int timeout_count = TIMEOUT_COUNT;
 114
 115         while (--timeout_count) {
 116                 can_write_dcc(reg);
 117                 if (reg)
 118                         break;
 119         }
 120         if (timeout_count == 0)
 121                 return;
 122         else
 123                 write_dcc(ch);
 124 }
 125
 126 static void arm_dcc_puts(const char *s)
 127 {
 128         while (*s)
 129                 arm_dcc_putc(*s++);
 130 }
 131
 132 static int arm_dcc_tstc(void)
 133 {
 134         register unsigned int reg;
 135
 136         can_read_dcc(reg);
 137
 138         return reg;
 139 }
 140
 141 static void arm_dcc_setbrg(void)
 142 {
 143 }
 144
 145 static struct serial_device arm_dcc_drv = {
 146         .name   = "arm_dcc",
 147         .start  = arm_dcc_init,
 148         .stop   = NULL,
 149         .setbrg = arm_dcc_setbrg,
 150         .putc   = arm_dcc_putc,
 151         .puts   = arm_dcc_puts,
 152         .getc   = arm_dcc_getc,
 153         .tstc   = arm_dcc_tstc,
 154 };
 155
 156 void arm_dcc_initialize(void)
 157 {
 158         serial_register(&arm_dcc_drv);
 159 }
 160
 161 __weak struct serial_device *default_serial_console(void)
 162 {
 163         return &arm_dcc_drv;
 164 }