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