Fix use of stale power states in PSCI standby finisher

A PSCI CPU_SUSPEND request to place a CPU in retention states at power levels
higher than the CPU power level is subject to the same state coordination as a
power down state. A CPU could implement multiple retention states at a
particular power level. When exiting WFI, the non-CPU power levels may be in a
different retention state to what was initially requested, therefore each CPU
should refresh its view of the states of all power levels.

Previously, a CPU re-used the state of the power levels when it entered the
retention state. This patch fixes this issue by ensuring that a CPU upon exit
from retention reads the state of each power level afresh.

Change-Id: I93b5f5065c63400c6fd2598dbaafac385748f989

3 files changed, 15 insertions, 5 deletions

diff --git a/lib/psci/psci_common.c b/lib/psci/psci_common.c
index c6fea5b0..e87e8c05 100644
--- a/lib/psci/psci_common.c
+++ b/lib/psci/psci_common.c
@@ -252,8 +252,8 @@ static plat_local_state_t *psci_get_req_local_pwr_states(unsigned int pwrlvl,
  * function will be called after a cpu is powered on to find the local state
  * each power domain has emerged from.
  *****************************************************************************/
-static void psci_get_target_local_pwr_states(unsigned int end_pwrlvl,
-					     psci_power_state_t *target_state)
+void psci_get_target_local_pwr_states(unsigned int end_pwrlvl,
+				      psci_power_state_t *target_state)
 {
 	unsigned int parent_idx, lvl;
 	plat_local_state_t *pd_state = target_state->pwr_domain_state;
diff --git a/lib/psci/psci_private.h b/lib/psci/psci_private.h
index 49352144..b795c8e0 100644
--- a/lib/psci/psci_private.h
+++ b/lib/psci/psci_private.h
@@ -192,6 +192,8 @@ int psci_validate_power_state(unsigned int power_state,
 void psci_query_sys_suspend_pwrstate(psci_power_state_t *state_info);
 int psci_validate_mpidr(u_register_t mpidr);
 void psci_init_req_local_pwr_states(void);
+void psci_get_target_local_pwr_states(unsigned int end_pwrlvl,
+				      psci_power_state_t *target_state);
 int psci_validate_entry_point(entry_point_info_t *ep,
 			uintptr_t entrypoint, u_register_t context_id);
 void psci_get_parent_pwr_domain_nodes(unsigned int cpu_idx,
diff --git a/lib/psci/psci_suspend.c b/lib/psci/psci_suspend.c
index 904a4e75..0887e3b2 100644
--- a/lib/psci/psci_suspend.c
+++ b/lib/psci/psci_suspend.c
@@ -45,17 +45,25 @@
  * from standby/retention states at multiple power levels.
  ******************************************************************************/
 static void psci_suspend_to_standby_finisher(unsigned int cpu_idx,
-					     psci_power_state_t *state_info,
 					     unsigned int end_pwrlvl)
 {
+	psci_power_state_t state_info;
+
 	psci_acquire_pwr_domain_locks(end_pwrlvl,
 				cpu_idx);
 
 	/*
+	 * Find out which retention states this CPU has exited from until the
+	 * 'end_pwrlvl'. The exit retention state could be deeper than the entry
+	 * state as a result of state coordination amongst other CPUs post wfi.
+	 */
+	psci_get_target_local_pwr_states(end_pwrlvl, &state_info);
+
+	/*
 	 * Plat. management: Allow the platform to do operations
 	 * on waking up from retention.
 	 */
-	psci_plat_pm_ops->pwr_domain_suspend_finish(state_info);
+	psci_plat_pm_ops->pwr_domain_suspend_finish(&state_info);
 
 	/*
 	 * Set the requested and target state of this CPU and all the higher
@@ -222,7 +230,7 @@ exit:
 	 * After we wake up from context retaining suspend, call the
 	 * context retaining suspend finisher.
 	 */
-	psci_suspend_to_standby_finisher(idx, state_info, end_pwrlvl);
+	psci_suspend_to_standby_finisher(idx, end_pwrlvl);
 }
 
 /*******************************************************************************