Provide a hint to power controller for DSU cluster power down
By writing 0 to CLUSTERPWRDN DSU register bit 0, we send an
advisory to the power controller that cluster power is not required
when all cores are powered down.
The AArch32 CLUSTERPWRDN register is architecturally mapped to the
AArch64 CLUSTERPWRDN_EL1 register
Change-Id: Ie6e67c1c7d811fa25c51e2e405ca7f59bd20c81b
Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
diff --git a/plat/arm/css/common/css_pm.c b/plat/arm/css/common/css_pm.c
index af69c6f..8e74526 100644
--- a/plat/arm/css/common/css_pm.c
+++ b/plat/arm/css/common/css_pm.c
@@ -124,8 +124,28 @@
plat_arm_gic_cpuif_disable();
/* Cluster is to be turned off, so disable coherency */
- if (CSS_CLUSTER_PWR_STATE(target_state) == ARM_LOCAL_STATE_OFF)
+ if (CSS_CLUSTER_PWR_STATE(target_state) == ARM_LOCAL_STATE_OFF) {
plat_arm_interconnect_exit_coherency();
+
+#if HW_ASSISTED_COHERENCY
+ uint32_t reg;
+
+ /*
+ * If we have determined this core to be the last man standing and we
+ * intend to power down the cluster proactively, we provide a hint to
+ * the power controller that cluster power is not required when all
+ * cores are powered down.
+ * Note that this is only an advisory to power controller and is supported
+ * by SoCs with DynamIQ Shared Units only.
+ */
+ reg = read_clusterpwrdn();
+
+ /* Clear and set bit 0 : Cluster power not required */
+ reg &= ~DSU_CLUSTER_PWR_MASK;
+ reg |= DSU_CLUSTER_PWR_OFF;
+ write_clusterpwrdn(reg);
+#endif
+ }
}
/*******************************************************************************