OpenRISC: Idle/Power management

Minimal functionality...
Signed-off-by: Jonas Bonn <jonas@southpole.se>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>

arch/openrisc/kernel/idle.c

+/*
+ * OpenRISC idle.c
+ *
+ * Linux architectural port borrowing liberally from similar works of
+ * others.  All original copyrights apply as per the original source
+ * declaration.
+ *
+ * Modifications for the OpenRISC architecture:
+ * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com>
+ * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se>
+ *
+ *      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.
+ *
+ * Idle daemon for or32.  Idle daemon will handle any action
+ * that needs to be taken when the system becomes idle.
+ */
+
+#include <linux/errno.h>
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/smp.h>
+#include <linux/stddef.h>
+#include <linux/unistd.h>
+#include <linux/ptrace.h>
+#include <linux/slab.h>
+#include <linux/tick.h>
+
+#include <asm/pgtable.h>
+#include <asm/uaccess.h>
+#include <asm/system.h>
+#include <asm/io.h>
+#include <asm/processor.h>
+#include <asm/mmu.h>
+#include <asm/cache.h>
+#include <asm/pgalloc.h>
+
+void (*powersave) (void) = NULL;
+
+static inline void pm_idle(void)
+{
+	barrier();
+}
+
+void cpu_idle(void)
+{
+	set_thread_flag(TIF_POLLING_NRFLAG);
+
+	/* endless idle loop with no priority at all */
+	while (1) {
+		tick_nohz_stop_sched_tick(1);
+
+		while (!need_resched()) {
+			check_pgt_cache();
+			rmb();
+
+			clear_thread_flag(TIF_POLLING_NRFLAG);
+
+			local_irq_disable();
+			/* Don't trace irqs off for idle */
+			stop_critical_timings();
+			if (!need_resched() && powersave != NULL)
+				powersave();
+			start_critical_timings();
+			local_irq_enable();
+			set_thread_flag(TIF_POLLING_NRFLAG);
+		}
+
+		tick_nohz_restart_sched_tick();
+		preempt_enable_no_resched();
+		schedule();
+		preempt_disable();
+	}
+}