Write to HVC terminal from purgatory code

Current x86/x86-64 kexec-tools print the message "I'm in purgatory" to serial
console/VGA while executing the purgatory code.  Implement this feature for
POWERPC pseries platform by using the H_PUT_TERM_CHAR hypervisor call by
printng to hvc console.

Includes the changes suggested by Michael Ellerman

Signed-off-by: M. Mohan Kumar <mohan@in.ibm.com>
Signed-off-by: Simon Horman <horms@verge.net.au>

5 files changed, 50 insertions, 0 deletions

diff --git a/purgatory/arch/ppc64/Makefile b/purgatory/arch/ppc64/Makefile
index aaa4046..40a9e99 100644
--- a/purgatory/arch/ppc64/Makefile
+++ b/purgatory/arch/ppc64/Makefile
@@ -3,6 +3,7 @@
 #
 
 ppc64_PURGATORY_SRCS += purgatory/arch/ppc64/v2wrap.S
+ppc64_PURGATORY_SRCS += purgatory/arch/ppc64/hvCall.S
 ppc64_PURGATORY_SRCS += purgatory/arch/ppc64/purgatory-ppc64.c
 ppc64_PURGATORY_SRCS += purgatory/arch/ppc64/console-ppc64.c
 ppc64_PURGATORY_SRCS += purgatory/arch/ppc64/crashdump_backup.c
diff --git a/purgatory/arch/ppc64/console-ppc64.c b/purgatory/arch/ppc64/console-ppc64.c
index d6da7b3..78a233b 100644
--- a/purgatory/arch/ppc64/console-ppc64.c
+++ b/purgatory/arch/ppc64/console-ppc64.c
@@ -20,8 +20,22 @@
  */
 
 #include <purgatory.h>
+#include "hvCall.h"
+
+extern int debug;
 
 void putchar(int c)
 {
+	char buff[16];
+	unsigned long *lbuf = (unsigned long *)buff;
+
+	if (!debug) /* running on non pseries */
+		return;
+
+	if (c == '\n')
+		putchar('\r');
+
+	buff[0] = c;
+	plpar_hcall_norets(H_PUT_TERM_CHAR, 0, 1, lbuf[0], lbuf[1]);
 	return;
 }
diff --git a/purgatory/arch/ppc64/hvCall.S b/purgatory/arch/ppc64/hvCall.S
new file mode 100644
index 0000000..bdc4cb0
--- /dev/null
+++ b/purgatory/arch/ppc64/hvCall.S
@@ -0,0 +1,26 @@
+/*
+ * This file contains the generic function to perform a call to the
+ * pSeries LPAR hypervisor.
+ *
+ * Taken from linux/arch/powerpc/platforms/pseries/hvCall.S
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#define HVSC	.long 0x44000022
+.text
+	.machine ppc64
+.globl .plpar_hcall_norets
+.plpar_hcall_norets:
+	or	6,6,6			# medium low priority
+        mfcr	0
+        stw	0,8(1)
+
+        HVSC 				/* invoke the hypervisor */
+
+        lwz	0,8(1)
+        mtcrf	0xff,0
+        blr                             /* return r3 = status */
diff --git a/purgatory/arch/ppc64/hvCall.h b/purgatory/arch/ppc64/hvCall.h
new file mode 100644
index 0000000..187e24d
--- /dev/null
+++ b/purgatory/arch/ppc64/hvCall.h
@@ -0,0 +1,8 @@
+#ifndef HVCALL_H
+#define HVCALL_H
+
+#define H_PUT_TERM_CHAR	0x58
+
+long plpar_hcall_norets(unsigned long opcode, ...);
+
+#endif
diff --git a/purgatory/arch/ppc64/purgatory-ppc64.c b/purgatory/arch/ppc64/purgatory-ppc64.c
index 93f28d2..0b6d326 100644
--- a/purgatory/arch/ppc64/purgatory-ppc64.c
+++ b/purgatory/arch/ppc64/purgatory-ppc64.c
@@ -28,6 +28,7 @@ unsigned long stack = 0;
 unsigned long dt_offset = 0;
 unsigned long my_toc = 0;
 unsigned long kernel = 0;
+unsigned int debug = 0;
 
 void setup_arch(void)
 {