76 lines
2.2 KiB
C
76 lines
2.2 KiB
C
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/*
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* kmsg dumper that ensures the OPAL console fully flushes panic messages
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*
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* Author: Russell Currey <ruscur@russell.cc>
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*
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* Copyright 2015 IBM Corporation.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 of the License, or (at your
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* option) any later version.
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*/
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#include <linux/kmsg_dump.h>
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#include <asm/opal.h>
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#include <asm/opal-api.h>
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/*
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* Console output is controlled by OPAL firmware. The kernel regularly calls
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* OPAL_POLL_EVENTS, which flushes some console output. In a panic state,
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* however, the kernel no longer calls OPAL_POLL_EVENTS and the panic message
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* may not be completely printed. This function does not actually dump the
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* message, it just ensures that OPAL completely flushes the console buffer.
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*/
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static void force_opal_console_flush(struct kmsg_dumper *dumper,
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enum kmsg_dump_reason reason)
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{
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int i;
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int64_t ret;
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/*
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* Outside of a panic context the pollers will continue to run,
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* so we don't need to do any special flushing.
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*/
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if (reason != KMSG_DUMP_PANIC)
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return;
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if (opal_check_token(OPAL_CONSOLE_FLUSH)) {
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ret = opal_console_flush(0);
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if (ret == OPAL_UNSUPPORTED || ret == OPAL_PARAMETER)
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return;
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/* Incrementally flush until there's nothing left */
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while (opal_console_flush(0) != OPAL_SUCCESS);
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} else {
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/*
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* If OPAL_CONSOLE_FLUSH is not implemented in the firmware,
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* the console can still be flushed by calling the polling
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* function enough times to flush the buffer. We don't know
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* how much output still needs to be flushed, but we can be
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* generous since the kernel is in panic and doesn't need
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* to do much else.
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*/
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printk(KERN_NOTICE "opal: OPAL_CONSOLE_FLUSH missing.\n");
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for (i = 0; i < 1024; i++) {
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opal_poll_events(NULL);
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}
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}
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}
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static struct kmsg_dumper opal_kmsg_dumper = {
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.dump = force_opal_console_flush
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};
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void __init opal_kmsg_init(void)
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{
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int rc;
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/* Add our dumper to the list */
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rc = kmsg_dump_register(&opal_kmsg_dumper);
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if (rc != 0)
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pr_err("opal: kmsg_dump_register failed; returned %d\n", rc);
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}
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