linux-kernel - [PATCH] serial: 8250_dw: Fix runtime PM and use _DEFINE_DEV_PM

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Message-ID: <20251030174142.2039122-1-a.shimko.dev@gmail.com>
Date: Thu, 30 Oct 2025 20:41:41 +0300
From: Artem Shimko <a.shimko.dev@...il.com>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>
Cc: a.shimko.dev@...il.com,
	linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org
Subject: [PATCH] serial: 8250_dw: Fix runtime PM and use _DEFINE_DEV_PM_OPS

Move pm_runtime_set_active() before UART port setup and registration to
prevent runtime PM from suspending the device during probe. This ensures
the device remains active throughout critical initialization phases like
dw8250_setup_port() and serial8250_register_8250_port().

Add proper error handling in dw8250_runtime_resume() to maintain clock
state consistency. If clk enable fails, roll back previously enabled pclk.

Replace deprecated RUNTIME_PM_OPS macro with _DEFINE_DEV_PM_OPS for
modern kernel compliance.

Signed-off-by: Artem Shimko <a.shimko.dev@...il.com>
---

Dear Maintainers,

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

Thank you for your consideration.
--
Best regards,
Artem

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

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index 710ae4d40aec..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;
@@ -741,19 +744,25 @@ 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;
 }
 
-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