s390/console: Make preferred console handling more consistent

Use the same code structure when determining preferred consoles for
Linux running as KVM guest as with Linux running in LPAR and z/VM
guest:

 - Extend the console_mode variable to cover vt220 and hvc consoles
 - Determine sensible console defaults in conmode_default()
 - Remove KVM-special handling in set_preferred_console()

Ensure that the sclp line mode console is also registered when the
vt220 console was selected to not change existing behavior that
someone might be relying on.

As an externally visible change, KVM guest users can now select
the 3270 or 3215 console devices using the conmode= kernel parameter,
provided that support for the corresponding driver was compiled into
the kernel.

Signed-off-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Signed-off-by: Jing Liu <liujbjl@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/setup.h

@@ -86,9 +86,13 @@ extern char vmpoff_cmd[];
 #define CONSOLE_IS_SCLP		(console_mode == 1)
 #define CONSOLE_IS_3215		(console_mode == 2)
 #define CONSOLE_IS_3270		(console_mode == 3)
+#define CONSOLE_IS_VT220	(console_mode == 4)
+#define CONSOLE_IS_HVC		(console_mode == 5)
 #define SET_CONSOLE_SCLP	do { console_mode = 1; } while (0)
 #define SET_CONSOLE_3215	do { console_mode = 2; } while (0)
 #define SET_CONSOLE_3270	do { console_mode = 3; } while (0)
+#define SET_CONSOLE_VT220	do { console_mode = 4; } while (0)
+#define SET_CONSOLE_HVC		do { console_mode = 5; } while (0)
 
 #define NSS_NAME_SIZE	8
 extern char kernel_nss_name[];

arch/s390/kernel/setup.c

@@ -130,17 +130,14 @@ __setup("condev=", condev_setup);
 
 static void __init set_preferred_console(void)
 {
-	if (MACHINE_IS_KVM) {
+	if (CONSOLE_IS_3215 || CONSOLE_IS_SCLP)
-		if (sclp.has_vt220)
-			add_preferred_console("ttyS", 1, NULL);
-		else if (sclp.has_linemode)
-			add_preferred_console("ttyS", 0, NULL);
-		else
-			add_preferred_console("hvc", 0, NULL);
-	} else if (CONSOLE_IS_3215 || CONSOLE_IS_SCLP)
 		add_preferred_console("ttyS", 0, NULL);
 	else if (CONSOLE_IS_3270)
 		add_preferred_console("tty3270", 0, NULL);
+	else if (CONSOLE_IS_VT220)
+		add_preferred_console("ttyS", 1, NULL);
+	else if (CONSOLE_IS_HVC)
+		add_preferred_console("hvc", 0, NULL);
 }
 
 static int __init conmode_setup(char *str)
@@ -206,6 +203,15 @@ static void __init conmode_default(void)
 			SET_CONSOLE_SCLP;
 #endif
 		}
+	} else if (MACHINE_IS_KVM) {
+		if (sclp.has_vt220 &&
+		    config_enabled(CONFIG_SCLP_VT220_CONSOLE))
+			SET_CONSOLE_VT220;
+		else if (sclp.has_linemode &&
+			 config_enabled(CONFIG_SCLP_CONSOLE))
+			SET_CONSOLE_SCLP;
+		else
+			SET_CONSOLE_HVC;
 	} else {
 #if defined(CONFIG_SCLP_CONSOLE) || defined(CONFIG_SCLP_VT220_CONSOLE)
 		SET_CONSOLE_SCLP;

drivers/s390/char/sclp_con.c

@@ -319,7 +319,8 @@ sclp_console_init(void)
 	int i;
 	int rc;
 
-	if (!CONSOLE_IS_SCLP)
+	/* SCLP consoles are handled together */
+	if (!(CONSOLE_IS_SCLP || CONSOLE_IS_VT220))
 		return 0;
 	rc = sclp_rw_init();
 	if (rc)