nds32: Power management for nds32

There are three sleep states in nds32:
	suspend to idle,
	suspend to standby,
	suspend to ram

In suspend to ram, we use the 'standby' instruction to emulate
power management device to hang the system util wakeup source
send wakeup events to break the loop.

First, we push the general purpose registers and system registers
to stack. Second, we translate stack pointer to physical address
and store to memory to save the stack pointer. Third, after write
back and invalid the cache we hang in 'standby' intruction.
When wakeup source trigger wake up events, the loop will be break
and resume the system.

Signed-off-by: Nick Hu <nickhu@andestech.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Acked-by: Greentime Hu <greentime@andestech.com>
Signed-off-by: Greentime Hu <greentime@andestech.com>

arch/nds32/kernel/pm.c

@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2008-2017 Andes Technology Corporation
+
+#include <linux/init.h>
+#include <linux/suspend.h>
+#include <linux/device.h>
+#include <linux/printk.h>
+#include <linux/suspend.h>
+#include <asm/suspend.h>
+#include <nds32_intrinsic.h>
+
+unsigned int resume_addr;
+unsigned int *phy_addr_sp_tmp;
+
+static void nds32_suspend2ram(void)
+{
+	pgd_t *pgdv;
+	pud_t *pudv;
+	pmd_t *pmdv;
+	pte_t *ptev;
+
+	pgdv = (pgd_t *)__va((__nds32__mfsr(NDS32_SR_L1_PPTB) &
+		L1_PPTB_mskBASE)) + pgd_index((unsigned int)cpu_resume);
+
+	pudv = pud_offset(pgdv, (unsigned int)cpu_resume);
+	pmdv = pmd_offset(pudv, (unsigned int)cpu_resume);
+	ptev = pte_offset_map(pmdv, (unsigned int)cpu_resume);
+
+	resume_addr = ((*ptev) & TLB_DATA_mskPPN)
+			| ((unsigned int)cpu_resume & 0x00000fff);
+
+	suspend2ram();
+}
+
+static void nds32_suspend_cpu(void)
+{
+	while (!(__nds32__mfsr(NDS32_SR_INT_PEND) & wake_mask))
+		__asm__ volatile ("standby no_wake_grant\n\t");
+}
+
+static int nds32_pm_valid(suspend_state_t state)
+{
+	switch (state) {
+	case PM_SUSPEND_ON:
+	case PM_SUSPEND_STANDBY:
+	case PM_SUSPEND_MEM:
+		return 1;
+	default:
+		return 0;
+	}
+}
+
+static int nds32_pm_enter(suspend_state_t state)
+{
+	pr_debug("%s:state:%d\n", __func__, state);
+	switch (state) {
+	case PM_SUSPEND_STANDBY:
+		nds32_suspend_cpu();
+		return 0;
+	case PM_SUSPEND_MEM:
+		nds32_suspend2ram();
+		return 0;
+	default:
+		return -EINVAL;
+	}
+}
+
+static const struct platform_suspend_ops nds32_pm_ops = {
+	.valid = nds32_pm_valid,
+	.enter = nds32_pm_enter,
+};
+
+static int __init nds32_pm_init(void)
+{
+	pr_debug("Enter %s\n", __func__);
+	suspend_set_ops(&nds32_pm_ops);
+	return 0;
+}
+late_initcall(nds32_pm_init);