firmware: ti_sci: Introduce prepare system suspend call

Introduce a ti_sci_prepare_system_suspend call to be used in the driver
suspend handler to allow the system to identify the low power mode being
entered and if necessary, send TI_SCI_MSG_BEGIN_SLEEP with information
about the mode is being entered and the address for DDR memory carveout.

Signed-off-by: Dave Gerlach <d-gerlach@ti.com>
Signed-off-by: Vibhore Vardhan <vibhore@ti.com>

drivers/firmware/ti_sci.c

@@ -23,6 +23,7 @@
 #include <linux/slab.h>
 #include <linux/soc/ti/ti-msgmgr.h>
 #include <linux/soc/ti/ti_sci_protocol.h>
+#include <linux/suspend.h>
 #include <linux/reboot.h>
 
 #include "ti_sci.h"
@@ -3391,11 +3392,41 @@ static void ti_sci_set_is_suspending(struct ti_sci_info *info, bool is_suspendin
 	info->is_suspending = is_suspending;
 }
 
+static int ti_sci_prepare_system_suspend(struct ti_sci_info *info)
+{
+	int ret = 0;
+	int mode;
+
+	switch (pm_suspend_target_state) {
+	case PM_SUSPEND_MEM:
+		mode = TISCI_MSG_VALUE_SLEEP_MODE_DEEP_SLEEP;
+		break;
+	default:
+		ret = -EINVAL;
+	}
+
+	/*
+	 * Do not fail if we don't have action to take for a
+	 * specific suspend mode.
+	 */
+	if (ret)
+		return 0;
+
+	ret = ti_sci_cmd_prepare_sleep(&info->handle, mode, info->mem_ctx_lo,
+				       info->mem_ctx_hi, 0);
+
+	return ret;
+}
+
 static int ti_sci_suspend(struct device *dev)
 {
 	struct ti_sci_info *info = dev_get_drvdata(dev);
 	int ret = 0;
 
+	ret = ti_sci_prepare_system_suspend(info);
+	if (ret)
+		return ret;
+
 	/*
 	 * We must switch operation to polled mode now as drivers and the genpd
 	 * layer may make late TI SCI calls to change clock and device states