opal-kmsg.c

 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 */
22static void kmsg_dump_opal_console_flush(struct kmsg_dumper *dumper,
23				     struct kmsg_dump_detail *detail)
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 (detail->reason != KMSG_DUMP_PANIC)
30		return;
31
32	opal_flush_console(0);
33}
34
35static struct kmsg_dumper opal_kmsg_dumper = {
36	.dump = kmsg_dump_opal_console_flush
37};
38
39void __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}