1 files changed, 52 insertions, 0 deletions
diff --git a/arch/h8300/include/asm/switch_to.h b/arch/h8300/include/asm/switch_to.h
new file mode 100644
index 000000000..2b7e9555b
--- /dev/null
+++ b/arch/h8300/include/asm/switch_to.h
@@ -0,0 +1,52 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _H8300_SWITCH_TO_H
+#define _H8300_SWITCH_TO_H
+
+/*
+ * switch_to(n) should switch tasks to task ptr, first checking that
+ * ptr isn't the current task, in which case it does nothing.  This
+ * also clears the TS-flag if the task we switched to has used the
+ * math co-processor latest.
+ */
+/*
+ * switch_to() saves the extra registers, that are not saved
+ * automatically by SAVE_SWITCH_STACK in resume(), ie. d0-d5 and
+ * a0-a1. Some of these are used by schedule() and its predecessors
+ * and so we might get see unexpected behaviors when a task returns
+ * with unexpected register values.
+ *
+ * syscall stores these registers itself and none of them are used
+ * by syscall after the function in the syscall has been called.
+ *
+ * Beware that resume now expects *next to be in d1 and the offset of
+ * tss to be in a1. This saves a few instructions as we no longer have
+ * to push them onto the stack and read them back right after.
+ *
+ * 02/17/96 - Jes Sorensen (jds@kom.auc.dk)
+ *
+ * Changed 96/09/19 by Andreas Schwab
+ * pass prev in a0, next in a1, offset of tss in d1, and whether
+ * the mm structures are shared in d2 (to avoid atc flushing).
+ *
+ * H8/300 Porting 2002/09/04 Yoshinori Sato
+ */
+
+asmlinkage void resume(void);
+#define switch_to(prev, next, last) \
+do {			     \
+	void *_last;					    \
+	__asm__ __volatile__(				    \
+		"mov.l	%1, er0\n\t"			    \
+		"mov.l	%2, er1\n\t"			    \
+		"mov.l	%3, er2\n\t"			    \
+		"jsr @_resume\n\t"			    \
+		"mov.l	er2,%0\n\t"			    \
+		: "=r" (_last)				    \
+		: "r" (&(prev->thread)),		    \
+		  "r" (&(next->thread)),		    \
+		  "g" (prev)				    \
+		: "cc", "er0", "er1", "er2", "er3");	    \
+	(last) = _last;					    \
+} while (0)
+
+#endif /* _H8300_SWITCH_TO_H */