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  */
  22 static 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
  35 static struct kmsg_dumper opal_kmsg_dumper = {
  36         .dump = kmsg_dump_opal_console_flush
  37 };
  38
  39 void __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 }