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 kmsg_dump_opal_console_flush(struct kmsg_dumper *dumper,
27 				     enum kmsg_dump_reason reason)
28 {
29 	/*
30 	 * Outside of a panic context the pollers will continue to run,
31 	 * so we don't need to do any special flushing.
32 	 */
33 	if (reason != KMSG_DUMP_PANIC)
34 		return;
35 
36 	opal_flush_console(0);
37 }
38 
39 static struct kmsg_dumper opal_kmsg_dumper = {
40 	.dump = kmsg_dump_opal_console_flush
41 };
42 
43 void __init opal_kmsg_init(void)
44 {
45 	int rc;
46 
47 	/* Add our dumper to the list */
48 	rc = kmsg_dump_register(&opal_kmsg_dumper);
49 	if (rc != 0)
50 		pr_err("opal: kmsg_dump_register failed; returned %d\n", rc);
51 }
52