RISC-V: Task implementation

This patch contains the implementation of tasks on RISC-V, most of which
is involved in task switching.

Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>

1 files changed, 69 insertions, 0 deletions

diff --git a/arch/riscv/include/asm/switch_to.h b/arch/riscv/include/asm/switch_to.h
new file mode 100644
index 000000000000..dd6b05bff75b
--- /dev/null
+++ b/arch/riscv/include/asm/switch_to.h
@@ -0,0 +1,69 @@
+/*
+ * Copyright (C) 2012 Regents of the University of California
+ *
+ *   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, version 2.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ */
+
+#ifndef _ASM_RISCV_SWITCH_TO_H
+#define _ASM_RISCV_SWITCH_TO_H
+
+#include <asm/processor.h>
+#include <asm/ptrace.h>
+#include <asm/csr.h>
+
+extern void __fstate_save(struct task_struct *save_to);
+extern void __fstate_restore(struct task_struct *restore_from);
+
+static inline void __fstate_clean(struct pt_regs *regs)
+{
+	regs->sstatus |= (regs->sstatus & ~(SR_FS)) | SR_FS_CLEAN;
+}
+
+static inline void fstate_save(struct task_struct *task,
+			       struct pt_regs *regs)
+{
+	if ((regs->sstatus & SR_FS) == SR_FS_DIRTY) {
+		__fstate_save(task);
+		__fstate_clean(regs);
+	}
+}
+
+static inline void fstate_restore(struct task_struct *task,
+				  struct pt_regs *regs)
+{
+	if ((regs->sstatus & SR_FS) != SR_FS_OFF) {
+		__fstate_restore(task);
+		__fstate_clean(regs);
+	}
+}
+
+static inline void __switch_to_aux(struct task_struct *prev,
+				   struct task_struct *next)
+{
+	struct pt_regs *regs;
+
+	regs = task_pt_regs(prev);
+	if (unlikely(regs->sstatus & SR_SD))
+		fstate_save(prev, regs);
+	fstate_restore(next, task_pt_regs(next));
+}
+
+extern struct task_struct *__switch_to(struct task_struct *,
+				       struct task_struct *);
+
+#define switch_to(prev, next, last)			\
+do {							\
+	struct task_struct *__prev = (prev);		\
+	struct task_struct *__next = (next);		\
+	__switch_to_aux(__prev, __next);		\
+	((last) = __switch_to(__prev, __next));		\
+} while (0)
+
+#endif /* _ASM_RISCV_SWITCH_TO_H */