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affddff6 RC |
1 | /* |
2 | * kmsg dumper that ensures the OPAL console fully flushes panic messages | |
3 | * | |
4 | * Author: Russell Currey <ruscur@russell.cc> | |
5 | * | |
6 | * Copyright 2015 IBM Corporation. | |
7 | * | |
8 | * This program is free software; you can redistribute it and/or modify it | |
9 | * under the terms of the GNU General Public License as published by the | |
10 | * Free Software Foundation; either version 2 of the License, or (at your | |
11 | * option) any later version. | |
12 | */ | |
13 | ||
14 | #include <linux/kmsg_dump.h> | |
15 | ||
16 | #include <asm/opal.h> | |
17 | #include <asm/opal-api.h> | |
18 | ||
19 | /* | |
20 | * Console output is controlled by OPAL firmware. The kernel regularly calls | |
21 | * OPAL_POLL_EVENTS, which flushes some console output. In a panic state, | |
22 | * however, the kernel no longer calls OPAL_POLL_EVENTS and the panic message | |
23 | * may not be completely printed. This function does not actually dump the | |
24 | * message, it just ensures that OPAL completely flushes the console buffer. | |
25 | */ | |
26 | static void force_opal_console_flush(struct kmsg_dumper *dumper, | |
27 | enum kmsg_dump_reason reason) | |
28 | { | |
29 | int i; | |
c88c5d43 | 30 | int64_t ret; |
affddff6 RC |
31 | |
32 | /* | |
33 | * Outside of a panic context the pollers will continue to run, | |
34 | * so we don't need to do any special flushing. | |
35 | */ | |
36 | if (reason != KMSG_DUMP_PANIC) | |
37 | return; | |
38 | ||
39 | if (opal_check_token(OPAL_CONSOLE_FLUSH)) { | |
c88c5d43 RC |
40 | ret = opal_console_flush(0); |
41 | ||
42 | if (ret == OPAL_UNSUPPORTED || ret == OPAL_PARAMETER) | |
43 | return; | |
44 | ||
45 | /* Incrementally flush until there's nothing left */ | |
46 | while (opal_console_flush(0) != OPAL_SUCCESS); | |
affddff6 RC |
47 | } else { |
48 | /* | |
49 | * If OPAL_CONSOLE_FLUSH is not implemented in the firmware, | |
50 | * the console can still be flushed by calling the polling | |
51 | * function enough times to flush the buffer. We don't know | |
52 | * how much output still needs to be flushed, but we can be | |
53 | * generous since the kernel is in panic and doesn't need | |
54 | * to do much else. | |
55 | */ | |
56 | printk(KERN_NOTICE "opal: OPAL_CONSOLE_FLUSH missing.\n"); | |
57 | for (i = 0; i < 1024; i++) { | |
58 | opal_poll_events(NULL); | |
59 | } | |
60 | } | |
61 | } | |
62 | ||
63 | static struct kmsg_dumper opal_kmsg_dumper = { | |
64 | .dump = force_opal_console_flush | |
65 | }; | |
66 | ||
67 | void __init opal_kmsg_init(void) | |
68 | { | |
69 | int rc; | |
70 | ||
71 | /* Add our dumper to the list */ | |
72 | rc = kmsg_dump_register(&opal_kmsg_dumper); | |
73 | if (rc != 0) | |
74 | pr_err("opal: kmsg_dump_register failed; returned %d\n", rc); | |
75 | } |