arch/powerpc/platforms/powernv/opal-kmsg.c

   1 /*
   2  * kmsg dumper that ensures the OPAL console fully flushes panic messages
   3  *
   4  * Author: Russell Currey <ruscur@russell.cc>
   5  *
   6  * Copyright 2015 IBM Corporation.
   7  *
   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.
  12  */
  13
  14 #include <linux/kmsg_dump.h>
  15
  16 #include <asm/opal.h>
  17 #include <asm/opal-api.h>
  18
  19 /*
  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.
  25  */
  26 static void force_opal_console_flush(struct kmsg_dumper *dumper,
  27                                      enum kmsg_dump_reason reason)
  28 {
  29         int i;
  30         int64_t ret;
  31
  32         /*
  33          * Outside of a panic context the pollers will continue to run,
  34          * so we don't need to do any special flushing.
  35          */
  36         if (reason != KMSG_DUMP_PANIC)
  37                 return;
  38
  39         if (opal_check_token(OPAL_CONSOLE_FLUSH)) {
  40                 ret = opal_console_flush(0);
  41
  42                 if (ret == OPAL_UNSUPPORTED || ret == OPAL_PARAMETER)
  43                         return;
  44
  45                 /* Incrementally flush until there's nothing left */
  46                 while (opal_console_flush(0) != OPAL_SUCCESS);
  47         } else {
  48                 /*
  49                  * If OPAL_CONSOLE_FLUSH is not implemented in the firmware,
  50                  * the console can still be flushed by calling the polling
  51                  * function enough times to flush the buffer.  We don't know
  52                  * how much output still needs to be flushed, but we can be
  53                  * generous since the kernel is in panic and doesn't need
  54                  * to do much else.
  55                  */
  56                 printk(KERN_NOTICE "opal: OPAL_CONSOLE_FLUSH missing.\n");
  57                 for (i = 0; i < 1024; i++) {
  58                         opal_poll_events(NULL);
  59                 }
  60         }
  61 }
  62
  63 static struct kmsg_dumper opal_kmsg_dumper = {
  64         .dump = force_opal_console_flush
  65 };
  66
  67 void __init opal_kmsg_init(void)
  68 {
  69         int rc;
  70
  71         /* Add our dumper to the list */
  72         rc = kmsg_dump_register(&opal_kmsg_dumper);
  73         if (rc != 0)
  74                 pr_err("opal: kmsg_dump_register failed; returned %d\n", rc);
  75 }