s390/chsc: fix SEI usage on old FW levels

Using a notification type mask for the store event information chsc
is unsupported on some firmware levels. Retry SEI with that mask set
to zero (which is the old way of requesting only channel subsystem
related events).

Cc: <[e-mail]>
Reported-and-tested-by: Stefan Haberland <[e-mail]>
Reviewed-by: Peter Oberparleiter <[e-mail]>
Signed-off-by: Sebastian Ott <[e-mail]>
Signed-off-by: Martin Schwidefsky <[e-mail]>

drivers/s390/cio/chsc.c

···
 
 static void chsc_process_event_information(struct chsc_sei *sei, u64 ntsm)
 {
-	do {
+	static int ntsm_unsupported;
+
+	while (true) {
 		memset(sei, 0, sizeof(*sei));
 		sei->request.length = 0x0010;
 		sei->request.code = 0x000e;
-		sei->ntsm = ntsm;
+		if (!ntsm_unsupported)
+			sei->ntsm = ntsm;
 
 		if (chsc(sei))
 			break;
 
 		if (sei->response.code != 0x0001) {
-			CIO_CRW_EVENT(2, "chsc: sei failed (rc=%04x)\n",
-				      sei->response.code);
+			CIO_CRW_EVENT(2, "chsc: sei failed (rc=%04x, ntsm=%llx)\n",
+				      sei->response.code, sei->ntsm);
+
+			if (sei->response.code == 3 && sei->ntsm) {
+				/* Fallback for old firmware. */
+				ntsm_unsupported = 1;
+				continue;
+			}
 			break;
 		}
 
···
 			CIO_CRW_EVENT(2, "chsc: unhandled nt: %d\n", sei->nt);
 			break;
 		}
-	} while (sei->u.nt0_area.flags & 0x80);
+
+		if (!(sei->u.nt0_area.flags & 0x80))
+			break;
+	}
 }
 
 /*