Fix PSCI CPU ON race when setting state to ON_PENDING
When a CPU is powered down using PSCI CPU OFF API, it disables its caches
and updates its `aff_info_state` to OFF. The corresponding cache line is
invalidated by the CPU so that the update will be observed by other CPUs
running with caches enabled. There is a possibility that another CPU
which has been trying to turn ON this CPU via PSCI CPU ON API,
has already seen the update to `aff_info_state` and proceeds to update
the state to ON_PENDING prior to the cache invalidation. This may result
in the update of the state to ON_PENDING being discarded.
This patch fixes this issue by making sure that the update of `aff_info_state`
to ON_PENDING sticks by reading back the value after the cache flush and
retrying it if not updated. The patch also adds a dsbish() to
`psci_do_cpu_off()` to ensure ordering of the update to `aff_info_state`
prior to cache line invalidation.
Fixes ARM-software/tf-issues#349
Change-Id: I225de99957fe89871f8c57bcfc243956e805dcca
diff --git a/services/std_svc/psci/psci_private.h b/services/std_svc/psci/psci_private.h
index 3286cf6..4b91ad5 100644
--- a/services/std_svc/psci/psci_private.h
+++ b/services/std_svc/psci/psci_private.h
@@ -78,6 +78,9 @@
get_cpu_data(psci_svc_cpu_data.aff_info_state)
#define psci_get_aff_info_state_by_idx(idx) \
get_cpu_data_by_index(idx, psci_svc_cpu_data.aff_info_state)
+#define psci_set_aff_info_state_by_idx(idx, aff_state) \
+ set_cpu_data_by_index(idx, psci_svc_cpu_data.aff_info_state,\
+ aff_state)
#define psci_get_suspend_pwrlvl() \
get_cpu_data(psci_svc_cpu_data.target_pwrlvl)
#define psci_set_suspend_pwrlvl(target_lvl) \