[PATCH] i2c: designware: add reset control support in suspend/resume

[Artem Shimko <a.shimko.dev@gmail.com>]

The driver currently acquires reset control during probe but does not
manage it during system suspend/resume. This can leave the I2C controller
in an undefined state after resume.

Add reset control assertion during system suspend and deassertion during
resume to ensure proper hardware initialization across power management
transitions. Skip runtime suspend if the device is already suspended to
avoid redundant operations.

Signed-off-by: Artem Shimko <a.shimko.dev@gmail.com>
---
Hello maintainers and reviewers,

This patch adds proper reset control handling to the suspend/resume
callbacks. The reset line is asserted during system suspend to ensure
the controller is properly quiesced, and deasserted during resume to
reinitialize the hardware. Additionally, the suspend path now checks
the runtime PM status to avoid redundant operations when the device is
already suspended.

Thank you!
--
Regards,
Artem

 drivers/i2c/busses/i2c-designware-common.c | 40 ++++++++++++++++++----
 1 file changed, 34 insertions(+), 6 deletions(-)

diff --git a/drivers/i2c/busses/i2c-designware-common.c b/drivers/i2c/busses/i2c-designware-common.c
index 4dc57fd56170..fbe817df9b2e 100644
--- a/drivers/i2c/busses/i2c-designware-common.c
+++ b/drivers/i2c/busses/i2c-designware-common.c
@@ -29,6 +29,7 @@
 #include <linux/pm_runtime.h>
 #include <linux/property.h>
 #include <linux/regmap.h>
+#include <linux/reset.h>
 #include <linux/swab.h>
 #include <linux/types.h>
 #include <linux/units.h>
@@ -967,6 +968,7 @@ int i2c_dw_probe(struct dw_i2c_dev *dev)
 }
 EXPORT_SYMBOL_GPL(i2c_dw_probe);
 
+#ifdef CONFIG_ACPI
 static int i2c_dw_prepare(struct device *device)
 {
 	/*
@@ -977,18 +979,23 @@ static int i2c_dw_prepare(struct device *device)
 	 */
 	return !has_acpi_companion(device);
 }
+#endif
 
 static int i2c_dw_runtime_suspend(struct device *device)
 {
 	struct dw_i2c_dev *dev = dev_get_drvdata(device);
+	int ret;
 
 	if (dev->shared_with_punit)
 		return 0;
 
 	i2c_dw_disable(dev);
-	i2c_dw_prepare_clk(dev, false);
 
-	return 0;
+	ret = reset_control_assert(dev->rst);
+	if (ret)
+		return ret;
+
+	return i2c_dw_prepare_clk(dev, false);
 }
 
 static int i2c_dw_suspend(struct device *device)
@@ -997,15 +1004,28 @@ static int i2c_dw_suspend(struct device *device)
 
 	i2c_mark_adapter_suspended(&dev->adapter);
 
-	return i2c_dw_runtime_suspend(device);
+	if (!pm_runtime_status_suspended(device))
+		return i2c_dw_runtime_suspend(device);
+
+	return 0;
 }
 
 static int i2c_dw_runtime_resume(struct device *device)
 {
 	struct dw_i2c_dev *dev = dev_get_drvdata(device);
+	int ret;
+
+	if (!dev->shared_with_punit) {
+		ret = i2c_dw_prepare_clk(dev, true);
+		if (ret)
+			return ret;
 
-	if (!dev->shared_with_punit)
-		i2c_dw_prepare_clk(dev, true);
+		ret = reset_control_deassert(dev->rst);
+		if (ret) {
+			i2c_dw_prepare_clk(dev, false);
+			return ret;
+		}
+	}
 
 	i2c_dw_init(dev);
 
@@ -1015,16 +1035,24 @@ static int i2c_dw_runtime_resume(struct device *device)
 static int i2c_dw_resume(struct device *device)
 {
 	struct dw_i2c_dev *dev = dev_get_drvdata(device);
+	int ret;
+
+	ret = i2c_dw_runtime_resume(device);
+	if (ret)
+		return ret;
 
-	i2c_dw_runtime_resume(device);
 	i2c_mark_adapter_resumed(&dev->adapter);
 
 	return 0;
 }
 
 EXPORT_GPL_DEV_PM_OPS(i2c_dw_dev_pm_ops) = {
+#ifdef CONFIG_ACPI
 	.prepare = pm_sleep_ptr(i2c_dw_prepare),
 	LATE_SYSTEM_SLEEP_PM_OPS(i2c_dw_suspend, i2c_dw_resume)
+#else
+	SYSTEM_SLEEP_PM_OPS(i2c_dw_suspend, i2c_dw_resume)
+#endif
 	RUNTIME_PM_OPS(i2c_dw_runtime_suspend, i2c_dw_runtime_resume, NULL)
 };
 
-- 
2.43.0