1 /* Copyright (c) 2010, 2014 The Linux Foundation. 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 13 #include <linux/init.h> 14 15 #include <asm/dcc.h> 16 #include <asm/processor.h> 17 18 #include "hvc_console.h" 19 20 /* DCC Status Bits */ 21 #define DCC_STATUS_RX (1 << 30) 22 #define DCC_STATUS_TX (1 << 29) 23 24 static int hvc_dcc_put_chars(uint32_t vt, const char *buf, int count) 25 { 26 int i; 27 28 for (i = 0; i < count; i++) { 29 while (__dcc_getstatus() & DCC_STATUS_TX) 30 cpu_relax(); 31 32 __dcc_putchar(buf[i]); 33 } 34 35 return count; 36 } 37 38 static int hvc_dcc_get_chars(uint32_t vt, char *buf, int count) 39 { 40 int i; 41 42 for (i = 0; i < count; ++i) 43 if (__dcc_getstatus() & DCC_STATUS_RX) 44 buf[i] = __dcc_getchar(); 45 else 46 break; 47 48 return i; 49 } 50 51 static bool hvc_dcc_check(void) 52 { 53 unsigned long time = jiffies + (HZ / 10); 54 55 /* Write a test character to check if it is handled */ 56 __dcc_putchar('\n'); 57 58 while (time_is_after_jiffies(time)) { 59 if (!(__dcc_getstatus() & DCC_STATUS_TX)) 60 return true; 61 } 62 63 return false; 64 } 65 66 static const struct hv_ops hvc_dcc_get_put_ops = { 67 .get_chars = hvc_dcc_get_chars, 68 .put_chars = hvc_dcc_put_chars, 69 }; 70 71 static int __init hvc_dcc_console_init(void) 72 { 73 int ret; 74 75 if (!hvc_dcc_check()) 76 return -ENODEV; 77 78 /* Returns -1 if error */ 79 ret = hvc_instantiate(0, 0, &hvc_dcc_get_put_ops); 80 81 return ret < 0 ? -ENODEV : 0; 82 } 83 console_initcall(hvc_dcc_console_init); 84 85 static int __init hvc_dcc_init(void) 86 { 87 struct hvc_struct *p; 88 89 if (!hvc_dcc_check()) 90 return -ENODEV; 91 92 p = hvc_alloc(0, 0, &hvc_dcc_get_put_ops, 128); 93 94 return PTR_ERR_OR_ZERO(p); 95 } 96 device_initcall(hvc_dcc_init); 97