powerpc/powernv: opal-kmsg standardise OPAL_BUSY handling

OPAL_CONSOLE_FLUSH is documented as being able to return OPAL_BUSY,
so implement the standard OPAL_BUSY handling for it.
Reviewed-by: Russell Currey <ruscur@russell.cc>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

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

@@ -12,6 +12,7 @@
  */
 
 #include <linux/kmsg_dump.h>
+#include <linux/delay.h>
 
 #include <asm/opal.h>
 #include <asm/opal-api.h>
@@ -26,8 +27,7 @@
 static void force_opal_console_flush(struct kmsg_dumper *dumper,
 				     enum kmsg_dump_reason reason)
 {
-	int i;
-	int64_t ret;
+	s64 rc;
 
 	/*
 	 * Outside of a panic context the pollers will continue to run,
@@ -37,14 +37,22 @@ static void force_opal_console_flush(struct kmsg_dumper *dumper,
 		return;
 
 	if (opal_check_token(OPAL_CONSOLE_FLUSH)) {
-		ret = opal_console_flush(0);
+		do  {
+			rc = OPAL_BUSY;
+			while (rc == OPAL_BUSY || rc == OPAL_BUSY_EVENT) {
+				rc = opal_console_flush(0);
+				if (rc == OPAL_BUSY_EVENT) {
+					mdelay(OPAL_BUSY_DELAY_MS);
+					opal_poll_events(NULL);
+				} else if (rc == OPAL_BUSY) {
+					mdelay(OPAL_BUSY_DELAY_MS);
+				}
+			}
+		} while (rc == OPAL_PARTIAL); /* More to flush */
 
-		if (ret == OPAL_UNSUPPORTED || ret == OPAL_PARAMETER)
-			return;
-
-		/* Incrementally flush until there's nothing left */
-		while (opal_console_flush(0) != OPAL_SUCCESS);
 	} else {
+		int i;
+
 		/*
 		 * If OPAL_CONSOLE_FLUSH is not implemented in the firmware,
 		 * the console can still be flushed by calling the polling