ti: k3: drivers: ti_sci: Use non-blocking TI-SCI messages for power down

Now that we have non-blocking TI-SCI functions we can initiate the shutdown
sequence from the PSCI handler without needing the ti_sci_proc_shutdown
helper function, which is removed. This gives us the greater control and
flexibility that will be needed when cluster power down sequences are added.

Signed-off-by: Andrew F. Davis <afd@ti.com>
diff --git a/plat/ti/k3/common/k3_psci.c b/plat/ti/k3/common/k3_psci.c
index 235e639..afe465e 100644
--- a/plat/ti/k3/common/k3_psci.c
+++ b/plat/ti/k3/common/k3_psci.c
@@ -13,6 +13,7 @@
 #include <lib/psci/psci.h>
 #include <plat/common/platform.h>
 
+#include <ti_sci_protocol.h>
 #include <k3_gicv3.h>
 #include <ti_sci.h>
 
@@ -90,9 +91,24 @@
 	proc = PLAT_PROC_START_ID + core_id;
 	device = PLAT_PROC_DEVICE_START_ID + core_id;
 
-	ret = ti_sci_proc_shutdown(proc, device);
+	/* Start by sending wait for WFI command */
+	ret = ti_sci_proc_wait_boot_status_no_wait(proc,
+			/*
+			 * Wait maximum time to give us the best chance to get
+			 * to WFI before this command timeouts
+			 */
+			UINT8_MAX, 100, UINT8_MAX, UINT8_MAX,
+			/* Wait for WFI */
+			PROC_BOOT_STATUS_FLAG_ARMV8_WFI, 0, 0, 0);
 	if (ret) {
-		ERROR("Request to stop core failed: %d\n", ret);
+		ERROR("Sending wait for WFI failed (%d)\n", ret);
+		return;
+	}
+
+	/* Now queue up the core shutdown request */
+	ret = ti_sci_device_put_no_wait(device);
+	if (ret) {
+		ERROR("Sending core shutdown message failed (%d)\n", ret);
 		return;
 	}
 }