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 asm volatile("mrc p14, 0, %0, c0, c1, 0 @ read comms ctrl reg" 37 : "=r" (__ret) : : "cc"); 38 39 return __ret; 40 } 41 42 43 static inline char __dcc_getchar(void) 44 { 45 char __c; 46 47 asm volatile("mrc p14, 0, %0, c0, c5, 0 @ read comms data reg" 48 : "=r" (__c)); 49 isb(); 50 51 return __c; 52 } 53 54 static inline void __dcc_putchar(char c) 55 { 56 asm volatile("mcr p14, 0, %0, c0, c5, 0 @ write a char" 57 : /* no output register */ 58 : "r" (c)); 59 isb(); 60 } 61 62 static int hvc_dcc_put_chars(uint32_t vt, const char *buf, int count) 63 { 64 int i; 65 66 for (i = 0; i < count; i++) { 67 while (__dcc_getstatus() & DCC_STATUS_TX) 68 cpu_relax(); 69 70 __dcc_putchar(buf[i]); 71 } 72 73 return count; 74 } 75 76 static int hvc_dcc_get_chars(uint32_t vt, char *buf, int count) 77 { 78 int i; 79 80 for (i = 0; i < count; ++i) 81 if (__dcc_getstatus() & DCC_STATUS_RX) 82 buf[i] = __dcc_getchar(); 83 else 84 break; 85 86 return i; 87 } 88 89 static bool hvc_dcc_check(void) 90 { 91 unsigned long time = jiffies + (HZ / 10); 92 93 /* Write a test character to check if it is handled */ 94 __dcc_putchar('\n'); 95 96 while (time_is_after_jiffies(time)) { 97 if (!(__dcc_getstatus() & DCC_STATUS_TX)) 98 return true; 99 } 100 101 return false; 102 } 103 104 static const struct hv_ops hvc_dcc_get_put_ops = { 105 .get_chars = hvc_dcc_get_chars, 106 .put_chars = hvc_dcc_put_chars, 107 }; 108 109 static int __init hvc_dcc_console_init(void) 110 { 111 if (!hvc_dcc_check()) 112 return -ENODEV; 113 114 hvc_instantiate(0, 0, &hvc_dcc_get_put_ops); 115 return 0; 116 } 117 console_initcall(hvc_dcc_console_init); 118 119 static int __init hvc_dcc_init(void) 120 { 121 if (!hvc_dcc_check()) 122 return -ENODEV; 123 124 hvc_alloc(0, 0, &hvc_dcc_get_put_ops, 128); 125 return 0; 126 } 127 device_initcall(hvc_dcc_init); 128