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  * SPDX-License-Identifier:     GPL-2.0
   6  *
   7  * As a special exception, if other files instantiate templates or use macros
   8  * or inline functions from this file, or you compile this file and link it
   9  * with other works to produce a work based on this file, this file does not
  10  * by itself cause the resulting work to be covered by the GNU General Public
  11  * License. However the source code for this file must still be made available
  12  * in accordance with section (3) of the GNU General Public License.
  13
  14  * This exception does not invalidate any other reasons why a work based on
  15  * this file might be covered by the GNU General Public License.
  16  */
  17
  18 #include <common.h>
  19 #include <serial.h>
  20
  21 #if defined(CONFIG_CPU_V6) || defined(CONFIG_CPU_V7)
  22 /*
  23  * ARMV6 & ARMV7
  24  */
  25 #define DCC_RBIT        (1 << 30)
  26 #define DCC_WBIT        (1 << 29)
  27
  28 #define write_dcc(x)    \
  29                 __asm__ volatile ("mcr p14, 0, %0, c0, c5, 0\n" : : "r" (x))
  30
  31 #define read_dcc(x)     \
  32                 __asm__ volatile ("mrc p14, 0, %0, c0, c5, 0\n" : "=r" (x))
  33
  34 #define status_dcc(x)   \
  35                 __asm__ volatile ("mrc p14, 0, %0, c0, c1, 0\n" : "=r" (x))
  36
  37 #elif defined(CONFIG_CPU_XSCALE)
  38 /*
  39  * XSCALE
  40  */
  41 #define DCC_RBIT        (1 << 31)
  42 #define DCC_WBIT        (1 << 28)
  43
  44 #define write_dcc(x)    \
  45                 __asm__ volatile ("mcr p14, 0, %0, c8, c0, 0\n" : : "r" (x))
  46
  47 #define read_dcc(x)     \
  48                 __asm__ volatile ("mrc p14, 0, %0, c9, c0, 0\n" : "=r" (x))
  49
  50 #define status_dcc(x)   \
  51                 __asm__ volatile ("mrc p14, 0, %0, c14, c0, 0\n" : "=r" (x))
  52
  53 #elif defined(CONFIG_CPU_ARMV8)
  54 /*
  55  * ARMV8
  56  */
  57 #define DCC_RBIT        (1 << 30)
  58 #define DCC_WBIT        (1 << 29)
  59
  60 #define write_dcc(x)   \
  61                 __asm__ volatile ("msr dbgdtrtx_el0, %0\n" : : "r" (x))
  62
  63 #define read_dcc(x)    \
  64                 __asm__ volatile ("mrs %0, dbgdtrrx_el0\n" : "=r" (x))
  65
  66 #define status_dcc(x)  \
  67                 __asm__ volatile ("mrs %0, mdccsr_el0\n" : "=r" (x))
  68
  69 #else
  70 #define DCC_RBIT        (1 << 0)
  71 #define DCC_WBIT        (1 << 1)
  72
  73 #define write_dcc(x)    \
  74                 __asm__ volatile ("mcr p14, 0, %0, c1, c0, 0\n" : : "r" (x))
  75
  76 #define read_dcc(x)     \
  77                 __asm__ volatile ("mrc p14, 0, %0, c1, c0, 0\n" : "=r" (x))
  78
  79 #define status_dcc(x)   \
  80                 __asm__ volatile ("mrc p14, 0, %0, c0, c0, 0\n" : "=r" (x))
  81
  82 #endif
  83
  84 #define can_read_dcc(x) do {    \
  85                 status_dcc(x);  \
  86                 x &= DCC_RBIT;  \
  87                 } while (0);
  88
  89 #define can_write_dcc(x) do {   \
  90                 status_dcc(x);  \
  91                 x &= DCC_WBIT;  \
  92                 x = (x == 0);   \
  93                 } while (0);
  94
  95 #define TIMEOUT_COUNT 0x4000000
  96
  97 static int arm_dcc_init(void)
  98 {
  99         return 0;
 100 }
 101
 102 static int arm_dcc_getc(void)
 103 {
 104         int ch;
 105         register unsigned int reg;
 106
 107         do {
 108                 can_read_dcc(reg);
 109         } while (!reg);
 110         read_dcc(ch);
 111
 112         return ch;
 113 }
 114
 115 static void arm_dcc_putc(char ch)
 116 {
 117         register unsigned int reg;
 118         unsigned int timeout_count = TIMEOUT_COUNT;
 119
 120         while (--timeout_count) {
 121                 can_write_dcc(reg);
 122                 if (reg)
 123                         break;
 124         }
 125         if (timeout_count == 0)
 126                 return;
 127         else
 128                 write_dcc(ch);
 129 }
 130
 131 static int arm_dcc_tstc(void)
 132 {
 133         register unsigned int reg;
 134
 135         can_read_dcc(reg);
 136
 137         return reg;
 138 }
 139
 140 static void arm_dcc_setbrg(void)
 141 {
 142 }
 143
 144 static struct serial_device arm_dcc_drv = {
 145         .name   = "arm_dcc",
 146         .start  = arm_dcc_init,
 147         .stop   = NULL,
 148         .setbrg = arm_dcc_setbrg,
 149         .putc   = arm_dcc_putc,
 150         .puts   = default_serial_puts,
 151         .getc   = arm_dcc_getc,
 152         .tstc   = arm_dcc_tstc,
 153 };
 154
 155 void arm_dcc_initialize(void)
 156 {
 157         serial_register(&arm_dcc_drv);
 158 }
 159
 160 __weak struct serial_device *default_serial_console(void)
 161 {
 162         return &arm_dcc_drv;
 163 }