plat-sam: psci: add support for suspend and idle.

Based on the previous work to add suspend on sama5d2 platform, add
the PSCI glue to call suspend function. psci_cpu_suspend() is used to
put the platform in light suspend mode (STANDBY) whereas
psci_system_suspend() puts the system into the suspend mode selected by
CFG_ATMEL_PM_SUSPEND_MODE at compile time.

Acked-by: Etienne Carriere <etienne.carriere@linaro.org>
Signed-off-by: Clément Léger <clement.leger@bootlin.com>

core/arch/arm/plat-sam/pm/psci.c

@@ -5,12 +5,47 @@
 
 #include <drivers/atmel_rstc.h>
 #include <drivers/atmel_shdwc.h>
+#include <drivers/pm/sam/atmel_pm.h>
 #include <kernel/panic.h>
 #include <sm/psci.h>
 #include <sm/std_smc.h>
 #include <stdint.h>
 #include <trace.h>
 
+int psci_system_suspend(uintptr_t entry, uint32_t context_id __unused,
+			struct sm_nsec_ctx *nsec)
+{
+	if (!atmel_pm_suspend_available())
+		return PSCI_RET_NOT_SUPPORTED;
+
+	if (atmel_pm_suspend(entry, nsec))
+		return PSCI_RET_INTERNAL_FAILURE;
+
+	return PSCI_RET_SUCCESS;
+}
+
+int psci_cpu_suspend(uint32_t power_state,
+		     uintptr_t entry __unused, uint32_t context_id __unused,
+		     struct sm_nsec_ctx *nsec __unused)
+{
+	uint32_t type = 0;
+
+	if (atmel_pm_suspend_available())
+		return PSCI_RET_NOT_SUPPORTED;
+
+	type = (power_state & PSCI_POWER_STATE_TYPE_MASK) >>
+		PSCI_POWER_STATE_TYPE_SHIFT;
+
+	if (type != PSCI_POWER_STATE_TYPE_STANDBY) {
+		DMSG("Power state %x not supported", type);
+		return PSCI_RET_INVALID_PARAMETERS;
+	}
+
+	atmel_pm_cpu_idle();
+
+	return PSCI_RET_SUCCESS;
+}
+
 void __noreturn psci_system_off(void)
 {
 	if (!atmel_shdwc_available())
@@ -42,6 +77,11 @@ int psci_features(uint32_t psci_fid)
 		if (atmel_shdwc_available())
 			return PSCI_RET_SUCCESS;
 		return PSCI_RET_NOT_SUPPORTED;
+	case PSCI_CPU_SUSPEND:
+	case PSCI_SYSTEM_SUSPEND:
+		if (atmel_pm_suspend_available())
+			return PSCI_RET_SUCCESS;
+		return PSCI_RET_NOT_SUPPORTED;
 	default:
 		return PSCI_RET_NOT_SUPPORTED;
 	}