Add standby state support in PSCI cpu_suspend api

This patch adds support in the generic PSCI implementation to call a
platform specific function to enter a standby state using an example
implementation in ARM FVP port

Fixes ARM-software/tf-issues#94
Change-Id: Ic1263fcf25f28e09162ad29dca954125f9aa8cc9

include/psci.h

@@ -74,6 +74,9 @@
 #define PSTATE_TYPE_MASK	0x1
 #define PSTATE_AFF_LVL_MASK	0x3
 
+#define PSTATE_TYPE_STANDBY	0x0
+#define PSTATE_TYPE_POWERDOWN	0x1
+
 #define psci_get_pstate_id(pstate)	(pstate >> PSTATE_ID_SHIFT) & \
 					PSTATE_ID_MASK
 #define psci_get_pstate_type(pstate)	(pstate >> PSTATE_TYPE_SHIFT) & \

plat/fvp/plat_pm.c

@@ -43,6 +43,29 @@
 /* Only included for error codes */
 #include <psci.h>
 
+/*******************************************************************************
+ * FVP handler called when an affinity instance is about to enter standby.
+ ******************************************************************************/
+int fvp_affinst_standby(unsigned int power_state)
+{
+	unsigned int target_afflvl;
+
+	/* Sanity check the requested state */
+	target_afflvl = psci_get_pstate_afflvl(power_state);
+
+	/*
+	 * It's possible to enter standby only on affinity level 0 i.e. a cpu
+	 * on the FVP. Ignore any other affinity level.
+	 */
+	if (target_afflvl != MPIDR_AFFLVL0)
+		return PSCI_E_INVALID_PARAMS;
+
+	/* Enter standby state */
+	wfi();
+
+	return PSCI_E_SUCCESS;
+}
+
 /*******************************************************************************
  * FVP handler called when an affinity instance is about to be turned on. The
  * level and mpidr determine the affinity instance.
@@ -372,7 +395,7 @@ int fvp_affinst_suspend_finish(unsigned long mpidr,
  * Export the platform handlers to enable psci to invoke them
  ******************************************************************************/
 static plat_pm_ops fvp_plat_pm_ops = {
-	0,
+	fvp_affinst_standby,
 	fvp_affinst_on,
 	fvp_affinst_off,
 	fvp_affinst_suspend,

services/std_svc/psci/psci_main.c

@@ -85,20 +85,18 @@ int psci_cpu_suspend(unsigned int power_state,
 	unsigned long mpidr;
 	unsigned int target_afflvl, pstate_type;
 
-	/* TODO: Standby states are not supported at the moment */
-	pstate_type = psci_get_pstate_type(power_state);
-	if (pstate_type == 0) {
-		rc = PSCI_E_INVALID_PARAMS;
-		goto exit;
-	}
-
 	/* Sanity check the requested state */
 	target_afflvl = psci_get_pstate_afflvl(power_state);
-	if (target_afflvl > MPIDR_MAX_AFFLVL) {
-		rc = PSCI_E_INVALID_PARAMS;
-		goto exit;
-	}
+	if (target_afflvl > MPIDR_MAX_AFFLVL)
+		return PSCI_E_INVALID_PARAMS;
 
+	pstate_type = psci_get_pstate_type(power_state);
+	if (pstate_type == PSTATE_TYPE_STANDBY) {
+		if  (psci_plat_pm_ops->affinst_standby)
+			rc = psci_plat_pm_ops->affinst_standby(power_state);
+		else
+			return PSCI_E_INVALID_PARAMS;
+	} else {
 		mpidr = read_mpidr();
 		rc = psci_afflvl_suspend(mpidr,
 					 entrypoint,
@@ -106,10 +104,9 @@ int psci_cpu_suspend(unsigned int power_state,
 					 power_state,
 					 MPIDR_AFFLVL0,
 					 target_afflvl);
+	}
 
-exit:
-	if (rc != PSCI_E_SUCCESS)
-		assert(rc == PSCI_E_INVALID_PARAMS);
+	assert(rc == PSCI_E_INVALID_PARAMS || rc == PSCI_E_SUCCESS);
 	return rc;
 }