| 1 | |
| 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 | static 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 | static 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 | static 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 __init udbg_init_memcons(void)
|
| 96 | {
|
| 97 | udbg_putc = memcons_putc;
|
| 98 | udbg_getc = memcons_getc;
|
| 99 | udbg_getc_poll = memcons_getc_poll;
|
| 100 | }
|