ARM: OMAP2+: prm44xx: Inroduce cpu_pm notifiers for context save/restore

Inroduce cpu_pm notifiers for context save/restore. This will be
needed for am43xx family in case of rtc only mode with ddr in
self-refresh.
Signed-off-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/mach-omap2/prm44xx.c

@@ -12,6 +12,7 @@
  * published by the Free Software Foundation.
  */
 
+#include <linux/cpu_pm.h>
 #include <linux/kernel.h>
 #include <linux/delay.h>
 #include <linux/errno.h>
@@ -30,6 +31,7 @@
 #include "prcm44xx.h"
 #include "prminst44xx.h"
 #include "powerdomain.h"
+#include "pm.h"
 
 /* Static data */
 
@@ -768,6 +770,22 @@ void prm_restore_context(void)
 				 omap4_prcm_irq_setup.pm_ctrl);
 }
 
+static int cpu_notifier(struct notifier_block *nb, unsigned long cmd, void *v)
+{
+	switch (cmd) {
+	case CPU_CLUSTER_PM_ENTER:
+		if (enable_off_mode)
+			prm_save_context();
+		break;
+	case CPU_CLUSTER_PM_EXIT:
+		if (enable_off_mode)
+			prm_restore_context();
+		break;
+	}
+
+	return NOTIFY_OK;
+}
+
 /*
  * XXX document
  */
@@ -788,6 +806,7 @@ static const struct omap_prcm_init_data *prm_init_data;
 
 int __init omap44xx_prm_init(const struct omap_prcm_init_data *data)
 {
+	static struct notifier_block nb;
 	omap_prm_base_init();
 
 	prm_init_data = data;
@@ -809,6 +828,12 @@ int __init omap44xx_prm_init(const struct omap_prcm_init_data *data)
 		omap4_prcm_irq_setup.mask = AM43XX_PRM_IRQENABLE_MPU_OFFSET;
 	}
 
+	/* Only AM43XX can lose prm context during rtc-ddr suspend */
+	if (soc_is_am43xx()) {
+		nb.notifier_call = cpu_notifier;
+		cpu_pm_register_notifier(&nb);
+	}
+
 	return prm_register(&omap44xx_prm_ll_data);
 }