1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * kmsg dumper that ensures the OPAL console fully flushes panic messages
4  *
5  * Author: Russell Currey <ruscur@russell.cc>
6  *
7  * Copyright 2015 IBM Corporation.
8  */
9 
10 #include <linux/kmsg_dump.h>
11 
12 #include <asm/opal.h>
13 #include <asm/opal-api.h>
14 
15 /*
16  * Console output is controlled by OPAL firmware.  The kernel regularly calls
17  * OPAL_POLL_EVENTS, which flushes some console output.  In a panic state,
18  * however, the kernel no longer calls OPAL_POLL_EVENTS and the panic message
19  * may not be completely printed.  This function does not actually dump the
20  * message, it just ensures that OPAL completely flushes the console buffer.
21  */
22 static void kmsg_dump_opal_console_flush(struct kmsg_dumper *dumper,
23 				     enum kmsg_dump_reason reason)
24 {
25 	/*
26 	 * Outside of a panic context the pollers will continue to run,
27 	 * so we don't need to do any special flushing.
28 	 */
29 	if (reason != KMSG_DUMP_PANIC)
30 		return;
31 
32 	opal_flush_console(0);
33 }
34 
35 static struct kmsg_dumper opal_kmsg_dumper = {
36 	.dump = kmsg_dump_opal_console_flush
37 };
38 
39 void __init opal_kmsg_init(void)
40 {
41 	int rc;
42 
43 	/* Add our dumper to the list */
44 	rc = kmsg_dump_register(&opal_kmsg_dumper);
45 	if (rc != 0)
46 		pr_err("opal: kmsg_dump_register failed; returned %d\n", rc);
47 }
48