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 */
force_opal_console_flush(struct kmsg_dumper * dumper,enum kmsg_dump_reason reason)26 static void force_opal_console_flush(struct kmsg_dumper *dumper,
27 enum kmsg_dump_reason reason)
28 {
29 int i;
30 int64_t ret;
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)) {
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);
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
opal_kmsg_init(void)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 }
76