| b.liu | e958203 | 2025-04-17 19:18:16 +0800 | [diff] [blame^] | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
| 2 | /* |
| 3 | * A udbg backend which logs messages and reads input from in memory |
| 4 | * buffers. |
| 5 | * |
| 6 | * The console output can be read from memcons_output which is a |
| 7 | * circular buffer whose next write position is stored in memcons.output_pos. |
| 8 | * |
| 9 | * Input may be passed by writing into the memcons_input buffer when it is |
| 10 | * empty. The input buffer is empty when both input_pos == input_start and |
| 11 | * *input_start == '\0'. |
| 12 | * |
| 13 | * Copyright (C) 2003-2005 Anton Blanchard and Milton Miller, IBM Corp |
| 14 | * Copyright (C) 2013 Alistair Popple, IBM Corp |
| 15 | */ |
| 16 | |
| 17 | #include <linux/kernel.h> |
| 18 | #include <asm/barrier.h> |
| 19 | #include <asm/page.h> |
| 20 | #include <asm/processor.h> |
| 21 | #include <asm/udbg.h> |
| 22 | |
| 23 | struct memcons { |
| 24 | char *output_start; |
| 25 | char *output_pos; |
| 26 | char *output_end; |
| 27 | char *input_start; |
| 28 | char *input_pos; |
| 29 | char *input_end; |
| 30 | }; |
| 31 | |
| 32 | static char memcons_output[CONFIG_PPC_MEMCONS_OUTPUT_SIZE]; |
| 33 | static char memcons_input[CONFIG_PPC_MEMCONS_INPUT_SIZE]; |
| 34 | |
| 35 | struct memcons memcons = { |
| 36 | .output_start = memcons_output, |
| 37 | .output_pos = memcons_output, |
| 38 | .output_end = &memcons_output[CONFIG_PPC_MEMCONS_OUTPUT_SIZE], |
| 39 | .input_start = memcons_input, |
| 40 | .input_pos = memcons_input, |
| 41 | .input_end = &memcons_input[CONFIG_PPC_MEMCONS_INPUT_SIZE], |
| 42 | }; |
| 43 | |
| 44 | void memcons_putc(char c) |
| 45 | { |
| 46 | char *new_output_pos; |
| 47 | |
| 48 | *memcons.output_pos = c; |
| 49 | wmb(); |
| 50 | new_output_pos = memcons.output_pos + 1; |
| 51 | if (new_output_pos >= memcons.output_end) |
| 52 | new_output_pos = memcons.output_start; |
| 53 | |
| 54 | memcons.output_pos = new_output_pos; |
| 55 | } |
| 56 | |
| 57 | int memcons_getc_poll(void) |
| 58 | { |
| 59 | char c; |
| 60 | char *new_input_pos; |
| 61 | |
| 62 | if (*memcons.input_pos) { |
| 63 | c = *memcons.input_pos; |
| 64 | |
| 65 | new_input_pos = memcons.input_pos + 1; |
| 66 | if (new_input_pos >= memcons.input_end) |
| 67 | new_input_pos = memcons.input_start; |
| 68 | else if (*new_input_pos == '\0') |
| 69 | new_input_pos = memcons.input_start; |
| 70 | |
| 71 | *memcons.input_pos = '\0'; |
| 72 | wmb(); |
| 73 | memcons.input_pos = new_input_pos; |
| 74 | return c; |
| 75 | } |
| 76 | |
| 77 | return -1; |
| 78 | } |
| 79 | |
| 80 | int memcons_getc(void) |
| 81 | { |
| 82 | int c; |
| 83 | |
| 84 | while (1) { |
| 85 | c = memcons_getc_poll(); |
| 86 | if (c == -1) |
| 87 | cpu_relax(); |
| 88 | else |
| 89 | break; |
| 90 | } |
| 91 | |
| 92 | return c; |
| 93 | } |
| 94 | |
| 95 | void udbg_init_memcons(void) |
| 96 | { |
| 97 | udbg_putc = memcons_putc; |
| 98 | udbg_getc = memcons_getc; |
| 99 | udbg_getc_poll = memcons_getc_poll; |
| 100 | } |