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Diffstat (limited to 'kernel/arch/powerpc/platforms/powernv/opal-kmsg.c')
-rw-r--r--kernel/arch/powerpc/platforms/powernv/opal-kmsg.c75
1 files changed, 75 insertions, 0 deletions
diff --git a/kernel/arch/powerpc/platforms/powernv/opal-kmsg.c b/kernel/arch/powerpc/platforms/powernv/opal-kmsg.c
new file mode 100644
index 000000000..6f1214d4d
--- /dev/null
+++ b/kernel/arch/powerpc/platforms/powernv/opal-kmsg.c
@@ -0,0 +1,75 @@
+/*
+ * 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);
+}