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);
+}