[PATCH v4] i2c: cadence: Add shutdown handler

[Ajay Neeli <ajay.neeli@amd.com>]

During system reboot or kexec, in-flight I2C transfers can cause
spurious interrupts or leave the bus in an undefined state. Add a
shutdown handler that marks the adapter suspended and resets the
controller, ensuring a clean handoff.

Signed-off-by: Ajay Neeli <ajay.neeli@amd.com>
---
Link: https://lore.kernel.org/linux-i2c/20250730122907.18909-1-ajay.neeli@amd.com/

Changes v3->v4:
- Replaced disable_irq() with cdns_i2c_master_reset() to avoid
  potential deadlocks during shutdown
- Added pm_runtime_status_suspended() check to skip register access
  when clocks are disabled

Changes v2->v3:
Corrected a typo that caused a build error in v2

Changes in v1->v2:
Disable interrupts
---
 drivers/i2c/busses/i2c-cadence.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/i2c/busses/i2c-cadence.c b/drivers/i2c/busses/i2c-cadence.c
index 0fb728ade92e..da8770182a18 100644
--- a/drivers/i2c/busses/i2c-cadence.c
+++ b/drivers/i2c/busses/i2c-cadence.c
@@ -1635,6 +1635,25 @@ static void cdns_i2c_remove(struct platform_device *pdev)
 	reset_control_assert(id->reset);
 }
 
+/**
+ * cdns_i2c_shutdown - Prepare I2C controller for system shutdown
+ * @pdev:	Handle to the platform device structure
+ *
+ * Mark the adapter as suspended and reset the controller to ensure a clean
+ * handoff during system reboot or kexec.
+ */
+static void cdns_i2c_shutdown(struct platform_device *pdev)
+{
+	struct cdns_i2c *id = platform_get_drvdata(pdev);
+
+	/* Mark the adapter as suspended to prevent further I2C transfers */
+	i2c_mark_adapter_suspended(&id->adap);
+
+	/* Reset the controller state if active - clocks are disabled when suspended */
+	if (!pm_runtime_status_suspended(&pdev->dev))
+		cdns_i2c_master_reset(&id->adap);
+}
+
 static struct platform_driver cdns_i2c_drv = {
 	.driver = {
 		.name  = DRIVER_NAME,
@@ -1643,6 +1662,7 @@ static struct platform_driver cdns_i2c_drv = {
 	},
 	.probe  = cdns_i2c_probe,
 	.remove = cdns_i2c_remove,
+	.shutdown = cdns_i2c_shutdown,
 };
 
 module_platform_driver(cdns_i2c_drv);
-- 
2.43.0