feat(armv8/psci): Handle unexpected powerdown behavior

We've observed that some platforms behave unexpectedly when performing
power down. In these cases, after powerdown, the CPU cores are not awaken
by interrupts as expected by Bao. This commit solve this, by adding the
ability to skip the powerdown firmware call, instead relying on the
fallback mechanism of using standby.

Signed-off-by: David Cerdeira <[email protected]>

Author: DavidMCerdeira

src/arch/armv8/armv8-a/cpu.c

@@ -31,16 +31,7 @@ void cpu_arch_profile_idle()
 {
     int64_t err = psci_power_down(PSCI_WAKEUP_IDLE);
     if (err) {
-        switch (err) {
-            case PSCI_E_NOT_SUPPORTED:
-                /**
-                 * If power down is not supported let's just wait for an interrupt
-                 */
-                __asm__ volatile("wfi");
-                break;
-            default:
-                ERROR("PSCI cpu%d power down failed with error %ld", cpu()->id, err);
-        }
+        ERROR("PSCI cpu%d power down failed with error %ld", cpu()->id, err);
     }
 
     /**

src/arch/armv8/armv8-a/psci.c

@@ -90,6 +90,13 @@ int32_t psci_standby()
 
 int32_t psci_power_down(enum wakeup_reason reason)
 {
+    /* We've observed that some platforms behave unexpectedly when performing
+     * power down. In these cases, after powerdown, the CPU cores are not awaken
+     * by interrupts as expected by Bao. */
+    if (DEFINED(PLAT_PSCI_POWERDOWN_NOT_SUPPORTED)) {
+        return psci_standby();
+    }
+
     extern void psci_boot_entry(unsigned long x0);
 
     uint32_t pwr_state_aux = PSCI_POWER_STATE_LVL_0 | PSCI_STATE_TYPE_POWERDOWN;