MIPS: Malta: add suspend state entry code

This patch introduces code which will enter a suspend state via the
PIIX4. This can only be done when PCI support is enabled since it
requires access to PCI I/O space and the generation of a special cycle
on the PCI bus. In cases where PCI is disabled the mips_pm_suspend
function will simply always return an error.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/6905/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/mach-malta/malta-pm.h

@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2014 Imagination Technologies
+ * Author: Paul Burton <paul.burton@imgtec.com>
+ *
+ * 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.
+ */
+
+#ifndef __ASM_MIPS_MACH_MALTA_PM_H__
+#define __ASM_MIPS_MACH_MALTA_PM_H__
+
+#include <asm/mips-boards/piix4.h>
+
+#ifdef CONFIG_MIPS_MALTA_PM
+
+/**
+ * mips_pm_suspend - enter a suspend state
+ * @state: the state to enter, one of PIIX4_FUNC3IO_PMCNTRL_SUS_TYP_*
+ *
+ * Enters a suspend state via the Malta's PIIX4. If the state to be entered
+ * is one which loses context (eg. SOFF) then this function will never
+ * return.
+ */
+extern int mips_pm_suspend(unsigned state);
+
+#else /* !CONFIG_MIPS_MALTA_PM */
+
+static inline int mips_pm_suspend(unsigned state)
+{
+	return -EINVAL;
+}
+
+#endif /* !CONFIG_MIPS_MALTA_PM */
+
+#endif /* __ASM_MIPS_MACH_MALTA_PM_H__ */