s390/sclp: Add VT220 support to early sclp console

When running under qemu with the default configuration (-nographic),
there is only a VT220 SCLP console, no line-mode SCLP console. Add
VT220 support to the early SCLP console so the user has a chance to
see critical error messages during early boot.

None of the existing users of _sclp_print_early() check the return
code. Instead of trying to come up with return code semantics when
printing to multiple consoles (any or all of which may fail), we just
drop the return code entirely.

Tested on z/VM (line mode console) and LPAR (VT220 and line mode
console). Tested on qemu/KVM with VT220 console and / or line mode
console.
Signed-off-by: Sascha Silbe <silbe@linux.vnet.ibm.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/sclp.h

@@ -80,6 +80,6 @@ int sclp_pci_deconfigure(u32 fid);
 int memcpy_hsa_kernel(void *dest, unsigned long src, size_t count);
 int memcpy_hsa_user(void __user *dest, unsigned long src, size_t count);
 void sclp_early_detect(void);
-int _sclp_print_early(const char *);
+void _sclp_print_early(const char *);
 
 #endif /* _ASM_S390_SCLP_H */

arch/s390/kernel/sclp.c

@@ -9,7 +9,11 @@
 #include <asm/processor.h>
 #include <asm/sclp.h>
 
+#define EVTYP_VT220MSG_MASK	0x00000040
+#define EVTYP_MSG_MASK		0x40000000
+
 static char _sclp_work_area[4096] __aligned(PAGE_SIZE);
+static bool have_vt220, have_linemode;
 
 static void _sclp_wait_int(void)
 {
@@ -68,7 +72,7 @@ static int _sclp_setup(int disable)
 		0x00, 0x1c,
 		0x00, 0x00, 0x00, 0x00,	0x00, 0x00, 0x00, 0x00,
 		0x00, 0x04,
-		0x80, 0x00, 0x00, 0x00,	0x40, 0x00, 0x00, 0x00,
+		0x80, 0x00, 0x00, 0x00,	0x40, 0x00, 0x00, 0x40,
 		0x00, 0x00, 0x00, 0x00,	0x00, 0x00, 0x00, 0x00
 	};
 	unsigned int *masks;
@@ -82,13 +86,13 @@ static int _sclp_setup(int disable)
 	rc = _sclp_servc(0x00780005, _sclp_work_area);
 	if (rc)
 		return rc;
-	if ((masks[0] & masks[3]) != masks[0] ||
-	    (masks[1] & masks[2]) != masks[1])
-		return -EIO;
+	have_vt220 = masks[2] & EVTYP_VT220MSG_MASK;
+	have_linemode = masks[2] & EVTYP_MSG_MASK;
 	return 0;
 }
 
-static int _sclp_print(const char *str)
+/* Output multi-line text using SCLP Message interface. */
+static void _sclp_print_lm(const char *str)
 {
 	static unsigned char write_head[] = {
 		/* sccb header */
@@ -143,18 +147,49 @@ static int _sclp_print(const char *str)
 	} while (ch != 0);
 
 	/* SCLP write data */
-	return _sclp_servc(0x00760005, _sclp_work_area);
+	_sclp_servc(0x00760005, _sclp_work_area);
 }
 
-int _sclp_print_early(const char *str)
+/* Output multi-line text (plus a newline) using SCLP VT220
+ * interface.
+ */
+static void _sclp_print_vt220(const char *str)
 {
-	int rc;
+	static unsigned char const write_head[] = {
+		/* sccb header */
+		0x00, 0x0e,
+		0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+		/* evbuf header */
+		0x00, 0x06,
+		0x1a, 0x00, 0x00, 0x00,
+	};
+	size_t len = strlen(str);
 
-	rc = _sclp_setup(0);
-	if (rc)
-		return rc;
-	rc = _sclp_print(str);
-	if (rc)
-		return rc;
-	return _sclp_setup(1);
+	if (sizeof(write_head) + len >= sizeof(_sclp_work_area))
+		len = sizeof(_sclp_work_area) - sizeof(write_head) - 1;
+
+	memcpy(_sclp_work_area, write_head, sizeof(write_head));
+	memcpy(_sclp_work_area + sizeof(write_head), str, len);
+	_sclp_work_area[sizeof(write_head) + len] = '\n';
+
+	/* Update length fields in evbuf and sccb headers */
+	*(unsigned short *)(_sclp_work_area + 8) += len + 1;
+	*(unsigned short *)(_sclp_work_area + 0) += len + 1;
+
+	/* SCLP write data */
+	(void)_sclp_servc(0x00760005, _sclp_work_area);
+}
+
+/* Output one or more lines of text on the SCLP console (VT220 and /
+ * or line-mode). All lines get terminated; no need for a trailing LF.
+ */
+void _sclp_print_early(const char *str)
+{
+	if (_sclp_setup(0) != 0)
+		return;
+	if (have_linemode)
+		_sclp_print_lm(str);
+	if (have_vt220)
+		_sclp_print_vt220(str);
+	_sclp_setup(1);
 }