s390/ipl: Implement diag308 loop for zfcpdump

When a zfcpdump is triggered and a second dump on the same CEC is
already in progress for another LPAR, diagnose 308 returns with
an error code until the first dump is finished. Currently the
second Linux stops with a disabled wait PSW in that case.

This is improved now by by triggering diag 308 in a loop until
it works.
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/ipl.c

@@ -1414,6 +1414,16 @@ static struct kobj_attribute dump_type_attr =
 
 static struct kset *dump_kset;
 
+static void diag308_dump(void *dump_block)
+{
+	diag308(DIAG308_SET, dump_block);
+	while (1) {
+		if (diag308(DIAG308_DUMP, NULL) != 0x302)
+			break;
+		udelay_simple(USEC_PER_SEC);
+	}
+}
+
 static void __dump_run(void *unused)
 {
 	struct ccw_dev_id devid;
@@ -1432,12 +1442,10 @@ static void __dump_run(void *unused)
 		__cpcmd(buf, NULL, 0, NULL);
 		break;
 	case DUMP_METHOD_CCW_DIAG:
-		diag308(DIAG308_SET, dump_block_ccw);
-		diag308(DIAG308_DUMP, NULL);
+		diag308_dump(dump_block_ccw);
 		break;
 	case DUMP_METHOD_FCP_DIAG:
-		diag308(DIAG308_SET, dump_block_fcp);
-		diag308(DIAG308_DUMP, NULL);
+		diag308_dump(dump_block_fcp);
 		break;
 	default:
 		break;