1 /* 2 * A udbg backend which logs messages and reads input from in memory 3 * buffers. 4 * 5 * The console output can be read from memcons_output which is a 6 * circular buffer whose next write position is stored in memcons.output_pos. 7 * 8 * Input may be passed by writing into the memcons_input buffer when it is 9 * empty. The input buffer is empty when both input_pos == input_start and 10 * *input_start == '\0'. 11 * 12 * Copyright (C) 2003-2005 Anton Blanchard and Milton Miller, IBM Corp 13 * Copyright (C) 2013 Alistair Popple, IBM Corp 14 * 15 * This program is free software; you can redistribute it and/or 16 * modify it under the terms of the GNU General Public License 17 * as published by the Free Software Foundation; either version 18 * 2 of the License, or (at your option) any later version. 19 */ 20 21 #include <linux/kernel.h> 22 #include <asm/barrier.h> 23 #include <asm/page.h> 24 #include <asm/processor.h> 25 #include <asm/udbg.h> 26 27 struct memcons { 28 char *output_start; 29 char *output_pos; 30 char *output_end; 31 char *input_start; 32 char *input_pos; 33 char *input_end; 34 }; 35 36 static char memcons_output[CONFIG_PPC_MEMCONS_OUTPUT_SIZE]; 37 static char memcons_input[CONFIG_PPC_MEMCONS_INPUT_SIZE]; 38 39 struct memcons memcons = { 40 .output_start = memcons_output, 41 .output_pos = memcons_output, 42 .output_end = &memcons_output[CONFIG_PPC_MEMCONS_OUTPUT_SIZE], 43 .input_start = memcons_input, 44 .input_pos = memcons_input, 45 .input_end = &memcons_input[CONFIG_PPC_MEMCONS_INPUT_SIZE], 46 }; 47 48 void memcons_putc(char c) 49 { 50 char *new_output_pos; 51 52 *memcons.output_pos = c; 53 wmb(); 54 new_output_pos = memcons.output_pos + 1; 55 if (new_output_pos >= memcons.output_end) 56 new_output_pos = memcons.output_start; 57 58 memcons.output_pos = new_output_pos; 59 } 60 61 int memcons_getc_poll(void) 62 { 63 char c; 64 char *new_input_pos; 65 66 if (*memcons.input_pos) { 67 c = *memcons.input_pos; 68 69 new_input_pos = memcons.input_pos + 1; 70 if (new_input_pos >= memcons.input_end) 71 new_input_pos = memcons.input_start; 72 else if (*new_input_pos == '\0') 73 new_input_pos = memcons.input_start; 74 75 *memcons.input_pos = '\0'; 76 wmb(); 77 memcons.input_pos = new_input_pos; 78 return c; 79 } 80 81 return -1; 82 } 83 84 int memcons_getc(void) 85 { 86 int c; 87 88 while (1) { 89 c = memcons_getc_poll(); 90 if (c == -1) 91 cpu_relax(); 92 else 93 break; 94 } 95 96 return c; 97 } 98 99 void udbg_init_memcons(void) 100 { 101 udbg_putc = memcons_putc; 102 udbg_getc = memcons_getc; 103 udbg_getc_poll = memcons_getc_poll; 104 } 105