drivers/char/hvc_dcc.c

   1 /* Copyright (c) 2010, Code Aurora Forum. All rights reserved.
   2  *
   3  * This program is free software; you can redistribute it and/or modify
   4  * it under the terms of the GNU General Public License version 2 and
   5  * only version 2 as published by the Free Software Foundation.
   6  *
   7  * This program is distributed in the hope that it will be useful,
   8  * but WITHOUT ANY WARRANTY; without even the implied warranty of
   9  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  10  * GNU General Public License for more details.
  11  *
  12  * You should have received a copy of the GNU General Public License
  13  * along with this program; if not, write to the Free Software
  14  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  15  * 02110-1301, USA.
  16  */
  17
  18 #include <linux/console.h>
  19 #include <linux/delay.h>
  20 #include <linux/err.h>
  21 #include <linux/init.h>
  22 #include <linux/moduleparam.h>
  23 #include <linux/types.h>
  24
  25 #include <asm/processor.h>
  26
  27 #include "hvc_console.h"
  28
  29 /* DCC Status Bits */
  30 #define DCC_STATUS_RX           (1 << 30)
  31 #define DCC_STATUS_TX           (1 << 29)
  32
  33 static inline u32 __dcc_getstatus(void)
  34 {
  35         u32 __ret;
  36
  37         asm("mrc p14, 0, %0, c0, c1, 0  @ read comms ctrl reg"
  38                 : "=r" (__ret) : : "cc");
  39
  40         return __ret;
  41 }
  42
  43
  44 #if defined(CONFIG_CPU_V7)
  45 static inline char __dcc_getchar(void)
  46 {
  47         char __c;
  48
  49         asm("get_wait:  mrc p14, 0, pc, c0, c1, 0                          \n\
  50                         bne get_wait                                       \n\
  51                         mrc p14, 0, %0, c0, c5, 0       @ read comms data reg"
  52                 : "=r" (__c) : : "cc");
  53
  54         return __c;
  55 }
  56 #else
  57 static inline char __dcc_getchar(void)
  58 {
  59         char __c;
  60
  61         asm("mrc p14, 0, %0, c0, c5, 0  @ read comms data reg"
  62                 : "=r" (__c));
  63
  64         return __c;
  65 }
  66 #endif
  67
  68 #if defined(CONFIG_CPU_V7)
  69 static inline void __dcc_putchar(char c)
  70 {
  71         asm("put_wait:  mrc p14, 0, pc, c0, c1, 0                 \n\
  72                         bcs put_wait                              \n\
  73                         mcr p14, 0, %0, c0, c5, 0                   "
  74         : : "r" (c) : "cc");
  75 }
  76 #else
  77 static inline void __dcc_putchar(char c)
  78 {
  79         asm("mcr p14, 0, %0, c0, c5, 0  @ write a char"
  80                 : /* no output register */
  81                 : "r" (c));
  82 }
  83 #endif
  84
  85 static int hvc_dcc_put_chars(uint32_t vt, const char *buf, int count)
  86 {
  87         int i;
  88
  89         for (i = 0; i < count; i++) {
  90                 while (__dcc_getstatus() & DCC_STATUS_TX)
  91                         cpu_relax();
  92
  93                 __dcc_putchar((char)(buf[i] & 0xFF));
  94         }
  95
  96         return count;
  97 }
  98
  99 static int hvc_dcc_get_chars(uint32_t vt, char *buf, int count)
 100 {
 101         int i;
 102
 103         for (i = 0; i < count; ++i) {
 104                 int c = -1;
 105
 106                 if (__dcc_getstatus() & DCC_STATUS_RX)
 107                         c = __dcc_getchar();
 108                 if (c < 0)
 109                         break;
 110                 buf[i] = c;
 111         }
 112
 113         return i;
 114 }
 115
 116 static const struct hv_ops hvc_dcc_get_put_ops = {
 117         .get_chars = hvc_dcc_get_chars,
 118         .put_chars = hvc_dcc_put_chars,
 119 };
 120
 121 static int __init hvc_dcc_console_init(void)
 122 {
 123         hvc_instantiate(0, 0, &hvc_dcc_get_put_ops);
 124         return 0;
 125 }
 126 console_initcall(hvc_dcc_console_init);
 127
 128 static int __init hvc_dcc_init(void)
 129 {
 130         hvc_alloc(0, 0, &hvc_dcc_get_put_ops, 128);
 131         return 0;
 132 }
 133 device_initcall(hvc_dcc_init);