Introduce system suspend resume calls that will allow the ti_sci
driver to support deep sleep low power mode when the user space issues a
suspend to mem.

Also, write 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 TISCI_MSG_PREPARE_SLEEP with information
about the mode is being entered and the address for allocated memory for
storing the context during Deep Sleep.

We're using "pm_suspend_target_state" to map the kernel's target suspend
state to SysFW low power mode. Make sure this is available only when
CONFIG_SUSPEND is enabled.

Co-developed-by: Dave Gerlach <redacted>
Signed-off-by: Dave Gerlach <redacted>
Signed-off-by: Vibhore Vardhan <redacted>
Signed-off-by: Georgi Vlaev <redacted>
Signed-off-by: Dhruva Gole <redacted>
---
  drivers/firmware/ti_sci.c | 63 +++++++++++++++++++++++++++++++++++++++
  1 file changed, 63 insertions(+)

diff --git a/drivers/firmware/ti_sci.c b/drivers/firmware/ti_sci.c
index 0334ade19868..172b726e00a6 100644
--- a/drivers/firmware/ti_sci.c
+++ b/drivers/firmware/ti_sci.c

@@ -22,6 +22,7 @@
  #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"

@@ -3521,6 +3522,67 @@ static int tisci_reboot_handler(struct notifier_block *nb, unsigned long mode,
  	return NOTIFY_BAD;
  }
  
+static int ti_sci_prepare_system_suspend(struct ti_sci_info *info)
+{
+#if IS_ENABLED(CONFIG_SUSPEND)
+	u8 mode;
+
+	/* Map and validate the target Linux suspend state to TISCI LPM. */
+	switch (pm_suspend_target_state) {
+	case PM_SUSPEND_MEM:
+		/* S2MEM is not supported by the firmware. */
+		if (!(info->fw_caps & MSG_FLAG_CAPS_LPM_DEEP_SLEEP))
+			return 0;
+		mode = TISCI_MSG_VALUE_SLEEP_MODE_DEEP_SLEEP;
+		break;
+	default:
+		/*
+		 * Do not fail if we don't have action to take for a
+		 * specific suspend mode.
+		 */
+		return 0;
+	}
+
+	return ti_sci_cmd_prepare_sleep(&info->handle, mode,
+					(u32)(info->ctx_mem_addr & 0xffffffff),
+					(u32)((u64)info->ctx_mem_addr >> 32), 0);
+#else
+	return 0;
+#endif
+}
+
+static int ti_sci_suspend(struct device *dev)
+{
+	struct ti_sci_info *info = dev_get_drvdata(dev);
+	int ret;
+
+	ret = ti_sci_cmd_set_io_isolation(&info->handle, TISCI_MSG_VALUE_IO_ENABLE);

+	if (ret)
+		return ret;
+	dev_dbg(dev, "%s: set I/O isolation: %d\n", __func__, ret);
+
+	ret = ti_sci_prepare_system_suspend(info);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static int ti_sci_resume(struct device *dev)
+{
+	struct ti_sci_info *info = dev_get_drvdata(dev);
+	int ret;
+
+	ret = ti_sci_cmd_set_io_isolation(&info->handle, TISCI_MSG_VALUE_IO_DISABLE);
+	if (ret)
+		return ret;
+	dev_dbg(dev, "%s: disable I/O isolation: %d\n", __func__, ret);
+
+	return 0;
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(ti_sci_pm_ops, ti_sci_suspend, ti_sci_resume);
+
  static int ti_sci_init_suspend(struct platform_device *pdev,
  			       struct ti_sci_info *info)
  {

@@ -3759,6 +3821,7 @@ static struct platform_driver ti_sci_driver = {
  	.driver = {
  		   .name = "ti-sci",
  		   .of_match_table = of_match_ptr(ti_sci_of_match),
+		   .pm = &ti_sci_pm_ops,
  	},
  };
  module_platform_driver(ti_sci_driver);