[PATCH v2 0/2] serial: 8250_dw: Fix runtime PM and use _DEFINE_DEV_PM_OPS

[PATCH v2 0/2] serial: 8250_dw: Fix runtime PM and use _DEFINE_DEV_PM_OPS

[Artem Shimko]

Dear maintainers and reviewers,

This patch series enhances runtime power management error handling
in the 8250_dw driver and updates the PM ops initialization to
modern kernel standards.

The first patch adds proper error checking for clock enable operations
in runtime_resume, ensuring that failures are properly propagated
rather than silently ignored.

The second patch reorganizes the runtime PM initialization sequence
to simplify error handling and prevent potential suspend during
device probe.

Thank you for your consideration.

--
Best regards,
Artem Shimko

---

ChangeLog:
v1: https://lore.kernel.org/all/20251030174142.2039122-1-a.shimko.dev@gmail.com/T/#u
v2:
  * Split combined changes into separate logical commits
  * Added detailed commit messages explaining the changes

Artem Shimko (2):
  serial: 8250_dw: handle clock enable errors in runtime_resume
  serial: 8250_dw: fix runtime PM initialization sequence

 drivers/tty/serial/8250/8250_dw.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

-- 
2.43.0

[PATCH v2 1/2] serial: 8250_dw: handle clock enable errors in runtime_resume

[Artem Shimko]

Add error checking for clk_prepare_enable() calls in
dw8250_runtime_resume(). Currently if either clock fails to enable,
the function returns success while leaving clocks in inconsistent state.

This change implements comprehensive error handling by checking the return
values of both clk_prepare_enable() calls. If the second clock enable
operation fails after the first clock has already been successfully
enabled, the code now properly cleans up by disabling and unpreparing
the first clock before returning. The error code is then propagated to
the caller, ensuring that clock enable failures are properly reported
rather than being silently ignored.

Signed-off-by: Artem Shimko <a.shimko.dev@gmail.com>
---
 drivers/tty/serial/8250/8250_dw.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index 710ae4d40aec..0ff500965c10 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -741,11 +741,18 @@ static int dw8250_runtime_suspend(struct device *dev)
 
 static int dw8250_runtime_resume(struct device *dev)
 {
+	int ret;
 	struct dw8250_data *data = dev_get_drvdata(dev);
 
-	clk_prepare_enable(data->pclk);
+	ret = clk_prepare_enable(data->pclk);
+	if (ret)
+		return ret;
 
-	clk_prepare_enable(data->clk);
+	ret = clk_prepare_enable(data->clk);
+	if (ret) {
+		clk_disable_unprepare(data->pclk);
+		return ret;
+	}
 
 	return 0;
 }
-- 
2.43.0

[PATCH v2 2/2] serial: 8250_dw: fix runtime PM initialization sequence

[Artem Shimko]

Move pm_runtime_set_active() call earlier in probe to simplify error
handling and add proper error checking to ensure the device is marked
as active before any runtime PM operations can occur.

Additionally, replace the const struct dev_pm_ops declaration with
_DEFINE_DEV_PM_OPS macro for better consistency with modern kernel PM
patterns.

Signed-off-by: Artem Shimko <a.shimko.dev@gmail.com>
---
 drivers/tty/serial/8250/8250_dw.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index 0ff500965c10..0c0a9fc97fe3 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -643,6 +643,10 @@ static int dw8250_probe(struct platform_device *pdev)
 	if (err)
 		return err;
 
+	err = pm_runtime_set_active(dev);
+	if (err)
+		return dev_err_probe(dev, err, "Failed to set the runtime suspend as active\n");
+
 	data->uart_16550_compatible = device_property_read_bool(dev, "snps,uart-16550-compatible");
 
 	data->pdata = device_get_match_data(p->dev);
@@ -685,7 +689,6 @@ static int dw8250_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, data);
 
-	pm_runtime_set_active(dev);
 	pm_runtime_enable(dev);
 
 	return 0;
@@ -757,10 +760,9 @@ static int dw8250_runtime_resume(struct device *dev)
 	return 0;
 }
 
-static const struct dev_pm_ops dw8250_pm_ops = {
-	SYSTEM_SLEEP_PM_OPS(dw8250_suspend, dw8250_resume)
-	RUNTIME_PM_OPS(dw8250_runtime_suspend, dw8250_runtime_resume, NULL)
-};
+static _DEFINE_DEV_PM_OPS(dw8250_pm_ops, dw8250_suspend, dw8250_resume,
+			  dw8250_runtime_suspend, dw8250_runtime_resume,
+			  NULL);
 
 static const struct dw8250_platform_data dw8250_dw_apb = {
 	.usr_reg = DW_UART_USR,
-- 
2.43.0