2 * kmsg dumper that ensures the OPAL console fully flushes panic messages
4 * Author: Russell Currey <ruscur@russell.cc>
6 * Copyright 2015 IBM Corporation.
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.
14 #include <linux/kmsg_dump.h>
17 #include <asm/opal-api.h>
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.
26 static void force_opal_console_flush(struct kmsg_dumper
*dumper
,
27 enum kmsg_dump_reason reason
)
32 * Outside of a panic context the pollers will continue to run,
33 * so we don't need to do any special flushing.
35 if (reason
!= KMSG_DUMP_PANIC
)
38 if (opal_check_token(OPAL_CONSOLE_FLUSH
)) {
42 * If OPAL_CONSOLE_FLUSH is not implemented in the firmware,
43 * the console can still be flushed by calling the polling
44 * function enough times to flush the buffer. We don't know
45 * how much output still needs to be flushed, but we can be
46 * generous since the kernel is in panic and doesn't need
49 printk(KERN_NOTICE
"opal: OPAL_CONSOLE_FLUSH missing.\n");
50 for (i
= 0; i
< 1024; i
++) {
51 opal_poll_events(NULL
);
56 static struct kmsg_dumper opal_kmsg_dumper
= {
57 .dump
= force_opal_console_flush
60 void __init
opal_kmsg_init(void)
64 /* Add our dumper to the list */
65 rc
= kmsg_dump_register(&opal_kmsg_dumper
);
67 pr_err("opal: kmsg_dump_register failed; returned %d\n", rc
);