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diff --git a/lib/psci/psci_on.c b/lib/psci/psci_on.c
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+/*
+ * Copyright (c) 2013-2022, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <assert.h>
+#include <stddef.h>
+
+#include <arch.h>
+#include <arch_helpers.h>
+#include <common/bl_common.h>
+#include <common/debug.h>
+#include <lib/el3_runtime/context_mgmt.h>
+#include <lib/el3_runtime/pubsub_events.h>
+#include <plat/common/platform.h>
+
+#include "psci_private.h"
+
+/*
+ * Helper functions for the CPU level spinlocks
+ */
+static inline void psci_spin_lock_cpu(unsigned int idx)
+{
+ spin_lock(&psci_cpu_pd_nodes[idx].cpu_lock);
+}
+
+static inline void psci_spin_unlock_cpu(unsigned int idx)
+{
+ spin_unlock(&psci_cpu_pd_nodes[idx].cpu_lock);
+}
+
+/*******************************************************************************
+ * This function checks whether a cpu which has been requested to be turned on
+ * is OFF to begin with.
+ ******************************************************************************/
+static int cpu_on_validate_state(aff_info_state_t aff_state)
+{
+ if (aff_state == AFF_STATE_ON)
+ return PSCI_E_ALREADY_ON;
+
+ if (aff_state == AFF_STATE_ON_PENDING)
+ return PSCI_E_ON_PENDING;
+
+ assert(aff_state == AFF_STATE_OFF);
+ return PSCI_E_SUCCESS;
+}
+
+/*******************************************************************************
+ * Generic handler which is called to physically power on a cpu identified by
+ * its mpidr. It performs the generic, architectural, platform setup and state
+ * management to power on the target cpu e.g. it will ensure that
+ * enough information is stashed for it to resume execution in the non-secure
+ * security state.
+ *
+ * The state of all the relevant power domains are changed after calling the
+ * platform handler as it can return error.
+ ******************************************************************************/
+int psci_cpu_on_start(u_register_t target_cpu,
+ const entry_point_info_t *ep)
+{
+ int rc;
+ aff_info_state_t target_aff_state;
+ int ret = plat_core_pos_by_mpidr(target_cpu);
+ unsigned int target_idx = (unsigned int)ret;
+
+ /* Calling function must supply valid input arguments */
+ assert(ret >= 0);
+ assert(ep != NULL);
+
+
+ /*
+ * This function must only be called on platforms where the
+ * CPU_ON platform hooks have been implemented.
+ */
+ assert((psci_plat_pm_ops->pwr_domain_on != NULL) &&
+ (psci_plat_pm_ops->pwr_domain_on_finish != NULL));
+
+ /* Protect against multiple CPUs trying to turn ON the same target CPU */
+ psci_spin_lock_cpu(target_idx);
+
+ /*
+ * Generic management: Ensure that the cpu is off to be
+ * turned on.
+ * Perform cache maintanence ahead of reading the target CPU state to
+ * ensure that the data is not stale.
+ * There is a theoretical edge case where the cache may contain stale
+ * data for the target CPU data - this can occur under the following
+ * conditions:
+ * - the target CPU is in another cluster from the current
+ * - the target CPU was the last CPU to shutdown on its cluster
+ * - the cluster was removed from coherency as part of the CPU shutdown
+ *
+ * In this case the cache maintenace that was performed as part of the
+ * target CPUs shutdown was not seen by the current CPU's cluster. And
+ * so the cache may contain stale data for the target CPU.
+ */
+ flush_cpu_data_by_index(target_idx,
+ psci_svc_cpu_data.aff_info_state);
+ rc = cpu_on_validate_state(psci_get_aff_info_state_by_idx(target_idx));
+ if (rc != PSCI_E_SUCCESS)
+ goto exit;
+
+ /*
+ * Call the cpu on handler registered by the Secure Payload Dispatcher
+ * to let it do any bookeeping. If the handler encounters an error, it's
+ * expected to assert within
+ */
+ if ((psci_spd_pm != NULL) && (psci_spd_pm->svc_on != NULL))
+ psci_spd_pm->svc_on(target_cpu);
+
+ /*
+ * Set the Affinity info state of the target cpu to ON_PENDING.
+ * Flush aff_info_state as it will be accessed with caches
+ * turned OFF.
+ */
+ psci_set_aff_info_state_by_idx(target_idx, AFF_STATE_ON_PENDING);
+ flush_cpu_data_by_index(target_idx,
+ psci_svc_cpu_data.aff_info_state);
+
+ /*
+ * The cache line invalidation by the target CPU after setting the
+ * state to OFF (see psci_do_cpu_off()), could cause the update to
+ * aff_info_state to be invalidated. Retry the update if the target
+ * CPU aff_info_state is not ON_PENDING.
+ */
+ target_aff_state = psci_get_aff_info_state_by_idx(target_idx);
+ if (target_aff_state != AFF_STATE_ON_PENDING) {
+ assert(target_aff_state == AFF_STATE_OFF);
+ psci_set_aff_info_state_by_idx(target_idx, AFF_STATE_ON_PENDING);
+ flush_cpu_data_by_index(target_idx,
+ psci_svc_cpu_data.aff_info_state);
+
+ assert(psci_get_aff_info_state_by_idx(target_idx) ==
+ AFF_STATE_ON_PENDING);
+ }
+
+ /*
+ * Perform generic, architecture and platform specific handling.
+ */
+ /*
+ * Plat. management: Give the platform the current state
+ * of the target cpu to allow it to perform the necessary
+ * steps to power on.
+ */
+ rc = psci_plat_pm_ops->pwr_domain_on(target_cpu);
+ assert((rc == PSCI_E_SUCCESS) || (rc == PSCI_E_INTERN_FAIL));
+
+ if (rc == PSCI_E_SUCCESS)
+ /* Store the re-entry information for the non-secure world. */
+ cm_init_context_by_index(target_idx, ep);
+ else {
+ /* Restore the state on error. */
+ psci_set_aff_info_state_by_idx(target_idx, AFF_STATE_OFF);
+ flush_cpu_data_by_index(target_idx,
+ psci_svc_cpu_data.aff_info_state);
+ }
+
+exit:
+ psci_spin_unlock_cpu(target_idx);
+ return rc;
+}
+
+/*******************************************************************************
+ * The following function finish an earlier power on request. They
+ * are called by the common finisher routine in psci_common.c. The `state_info`
+ * is the psci_power_state from which this CPU has woken up from.
+ ******************************************************************************/
+void psci_cpu_on_finish(unsigned int cpu_idx, const psci_power_state_t *state_info)
+{
+ /*
+ * Plat. management: Perform the platform specific actions
+ * for this cpu e.g. enabling the gic or zeroing the mailbox
+ * register. The actual state of this cpu has already been
+ * changed.
+ */
+ psci_plat_pm_ops->pwr_domain_on_finish(state_info);
+
+#if !(HW_ASSISTED_COHERENCY || WARMBOOT_ENABLE_DCACHE_EARLY)
+ /*
+ * Arch. management: Enable data cache and manage stack memory
+ */
+ psci_do_pwrup_cache_maintenance();
+#endif
+
+ /*
+ * Plat. management: Perform any platform specific actions which
+ * can only be done with the cpu and the cluster guaranteed to
+ * be coherent.
+ */
+ if (psci_plat_pm_ops->pwr_domain_on_finish_late != NULL)
+ psci_plat_pm_ops->pwr_domain_on_finish_late(state_info);
+
+ /*
+ * All the platform specific actions for turning this cpu
+ * on have completed. Perform enough arch.initialization
+ * to run in the non-secure address space.
+ */
+ psci_arch_setup();
+
+ /*
+ * Lock the CPU spin lock to make sure that the context initialization
+ * is done. Since the lock is only used in this function to create
+ * a synchronization point with cpu_on_start(), it can be released
+ * immediately.
+ */
+ psci_spin_lock_cpu(cpu_idx);
+ psci_spin_unlock_cpu(cpu_idx);
+
+ /* Ensure we have been explicitly woken up by another cpu */
+ assert(psci_get_aff_info_state() == AFF_STATE_ON_PENDING);
+
+ /*
+ * Call the cpu on finish handler registered by the Secure Payload
+ * Dispatcher to let it do any bookeeping. If the handler encounters an
+ * error, it's expected to assert within
+ */
+ if ((psci_spd_pm != NULL) && (psci_spd_pm->svc_on_finish != NULL))
+ psci_spd_pm->svc_on_finish(0);
+
+ PUBLISH_EVENT(psci_cpu_on_finish);
+
+ /* Populate the mpidr field within the cpu node array */
+ /* This needs to be done only once */
+ psci_cpu_pd_nodes[cpu_idx].mpidr = read_mpidr() & MPIDR_AFFINITY_MASK;
+
+ /*
+ * Generic management: Now we just need to retrieve the
+ * information that we had stashed away during the cpu_on
+ * call to set this cpu on its way.
+ */
+ cm_prepare_el3_exit_ns();
+}