Subject: [PATCH 1/6] powerpc/powernv: opal-kmsg use flush fallback from console code

From: Nicholas Piggin <[email-masked]>
Date: Mon, 9 Apr 2018 15:40:51 +1000

Use the more refined and tested event polling loop from opal_put_chars
as the fallback console flush in the opal-kmsg path. This loop is used
by the console driver today, whereas the opal-kmsg fallback is not
likely to have been used for years.

Use WARN_ONCE rather than a printk when the fallback is invoked to
prepare for moving the console flush into a common function.

Cc: Russell Currey <[email-masked]>
Signed-off-by: Nicholas Piggin <[email-masked]>
---
 arch/powerpc/platforms/powernv/opal-kmsg.c | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/opal-kmsg.c b/arch/powerpc/platforms/powernv/opal-kmsg.c
index f8f41ccce75f..fd2bbf4fd6dc 100644
--- a/arch/powerpc/platforms/powernv/opal-kmsg.c
+++ b/arch/powerpc/platforms/powernv/opal-kmsg.c
@@ -51,20 +51,17 @@ static void force_opal_console_flush(struct kmsg_dumper *dumper,
 		} while (rc == OPAL_PARTIAL); /* More to flush */
 
 	} else {
-		int i;
+		__be64 evt;
 
+		WARN_ONCE(1, "opal: OPAL_CONSOLE_FLUSH missing.\n");
 		/*
 		 * 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.
+		 * function while it has OPAL_EVENT_CONSOLE_OUTPUT events.
 		 */
-		printk(KERN_NOTICE "opal: OPAL_CONSOLE_FLUSH missing.\n");
-		for (i = 0; i < 1024; i++) {
-			opal_poll_events(NULL);
-		}
+		do {
+			opal_poll_events(&evt);
+		} while (be64_to_cpu(evt) & OPAL_EVENT_CONSOLE_OUTPUT);
 	}
 }
 
-- 
2.17.0