ARM: mx51: Add support for low power suspend on MX51

Adds initial low power suspend functionality to MX51.
Supports "mem" and "standby" modes.

Tested on mx51-babbage.
Signed-off-by: Dinh Nguyen <Dinh.Nguyen@freescale.com>
Tested-by: Arnaud Patard <arnaud.patard@rtp-net.org>
Tested-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

arch/arm/mach-mx5/Makefile

@@ -6,6 +6,7 @@
 obj-y   := cpu.o mm.o clock-mx51-mx53.o devices.o ehci.o system.o
 obj-$(CONFIG_SOC_IMX50) += mm-mx50.o
 
+obj-$(CONFIG_PM) += pm-imx5.o
 obj-$(CONFIG_CPU_FREQ_IMX)    += cpu_op-mx51.o
 obj-$(CONFIG_MACH_MX51_BABBAGE) += board-mx51_babbage.o
 obj-$(CONFIG_MACH_MX51_3DS) += board-mx51_3ds.o

arch/arm/mach-mx5/pm-imx5.c

+/*
+ *  Copyright (C) 2011 Freescale Semiconductor, Inc. All Rights Reserved.
+ *
+ * The code contained herein is licensed under the GNU General Public
+ * License. You may obtain a copy of the GNU General Public License
+ * Version 2 or later at the following locations:
+ *
+ * http://www.opensource.org/licenses/gpl-license.html
+ * http://www.gnu.org/copyleft/gpl.html
+ */
+#include <linux/suspend.h>
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/err.h>
+#include <asm/cacheflush.h>
+#include <asm/tlbflush.h>
+#include <mach/system.h>
+#include "crm_regs.h"
+
+static struct clk *gpc_dvfs_clk;
+
+static int mx5_suspend_enter(suspend_state_t state)
+{
+	clk_enable(gpc_dvfs_clk);
+	switch (state) {
+	case PM_SUSPEND_MEM:
+		mx5_cpu_lp_set(STOP_POWER_OFF);
+		break;
+	case PM_SUSPEND_STANDBY:
+		mx5_cpu_lp_set(WAIT_UNCLOCKED_POWER_OFF);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	if (state == PM_SUSPEND_MEM) {
+		local_flush_tlb_all();
+		flush_cache_all();
+
+		/*clear the EMPGC0/1 bits */
+		__raw_writel(0, MXC_SRPG_EMPGC0_SRPGCR);
+		__raw_writel(0, MXC_SRPG_EMPGC1_SRPGCR);
+	}
+	cpu_do_idle();
+	clk_disable(gpc_dvfs_clk);
+
+	return 0;
+}
+
+static int mx5_pm_valid(suspend_state_t state)
+{
+	return (state > PM_SUSPEND_ON && state <= PM_SUSPEND_MAX);
+}
+
+static const struct platform_suspend_ops mx5_suspend_ops = {
+	.valid = mx5_pm_valid,
+	.enter = mx5_suspend_enter,
+};
+
+static int __init mx5_pm_init(void)
+{
+	if (gpc_dvfs_clk == NULL)
+		gpc_dvfs_clk = clk_get(NULL, "gpc_dvfs");
+
+	if (!IS_ERR(gpc_dvfs_clk)) {
+		if (cpu_is_mx51())
+			suspend_set_ops(&mx5_suspend_ops);
+	} else
+		return -EPERM;
+
+	return 0;
+}
+device_initcall(mx5_pm_init);