feat(psci): update PSCI_FEATURES

This patch updates the PSCI_FEATURES handler to indicate support for
OS-initiated mode per section 5.15.2 of the PSCI spec (DEN0022D.b) based
on the value of `FF_SUPPORTS_OS_INIT_MODE`, which is conditionally
enabled by the `PSCI_OS_INIT_MODE` build option.

Change-Id: I5da8a989b53419ad2ab55b73ddeee6e882c25554
Signed-off-by: Wing Li <wingers@google.com>

include/lib/psci/psci.h

@@ -143,7 +143,11 @@
 
 /* Features flags for CPU SUSPEND OS Initiated mode support. Bits [0:0] */
 #define FF_MODE_SUPPORT_SHIFT		U(0)
+#if PSCI_OS_INIT_MODE
 #define FF_SUPPORTS_OS_INIT_MODE	U(1)
+#else
+#define FF_SUPPORTS_OS_INIT_MODE	U(0)
+#endif
 
 /*******************************************************************************
  * PSCI version

lib/psci/psci_main.c

@@ -383,13 +383,9 @@ int psci_features(unsigned int psci_fid)
 	/* Format the feature flags */
 	if ((psci_fid == PSCI_CPU_SUSPEND_AARCH32) ||
 	    (psci_fid == PSCI_CPU_SUSPEND_AARCH64)) {
-		/*
-		 * The trusted firmware does not support OS Initiated Mode.
-		 */
 		unsigned int ret = ((FF_PSTATE << FF_PSTATE_SHIFT) |
-			(((FF_SUPPORTS_OS_INIT_MODE == 1U) ? 0U : 1U)
-				<< FF_MODE_SUPPORT_SHIFT));
-		return (int) ret;
+			(FF_SUPPORTS_OS_INIT_MODE << FF_MODE_SUPPORT_SHIFT));
+		return (int)ret;
 	}
 
 	/* Return 0 for all other fid's */
@@ -571,6 +567,10 @@ u_register_t psci_smc_handler(uint32_t smc_fid,
 			ret = psci_migrate_info_up_cpu();
 			break;
 
+		case PSCI_FEATURES:
+			ret = (u_register_t)psci_features(x1);
+			break;
+
 		case PSCI_NODE_HW_STATE_AARCH64:
 			ret = (u_register_t)psci_node_hw_state(
 					x1, (unsigned int) x2);