LXR linux/arch/powerpc/platforms/powernv/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                                     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
  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}
  48