Linux Serial subsystem development
 help / color / mirror / Atom feed
* [PATCH] serial: qcom-geni: remove .pm callback, use runtime PM in startup/shutdown
@ 2026-07-10  9:21 Praveen Talari
  2026-07-10 16:10 ` kernel test robot
  0 siblings, 1 reply; 2+ messages in thread
From: Praveen Talari @ 2026-07-10  9:21 UTC (permalink / raw)
  To: Greg Kroah-Hartman, Jiri Slaby, bjorn.andersson, Konrad Dybcio,
	Andy Shevchenko
  Cc: linux-arm-msm, linux-kernel, linux-serial, Mukesh Kumar Savaliya,
	aniket.randive, chandana.chiluveru, Praveen Talari

The driver currently relies on qcom_geni_serial_pm() through the
uart_ops.pm callback to manage runtime PM references. However, the
callback has a void return type, so failures from
pm_runtime_resume_and_get() cannot be propagated to the caller.

As a result, startup() may continue and access hardware even when the
runtime PM resume operation failed, leading to register accesses while
the device is not powered.

Move runtime PM acquisition to qcom_geni_serial_startup() and release it
to qcom_geni_serial_shutdown(). Since startup() can return an error, PM
resume failures are now detected and propagated before any hardware
initialization is performed. The startup/shutdown pair also provides a
natural place to balance runtime PM references for normal port usage.

During probe, uart_add_one_port() may configure the port before any user
opens the TTY, meaning startup() has not yet been called. To keep the
hardware powered during port registration, wrap uart_add_one_port() with
PM_RUNTIME_ACQUIRE_IF_ENABLED() and PM_RUNTIME_ACQUIRE_ERR(). This
ensures the device is resumed for the duration of registration and that
the runtime PM reference is automatically released afterwards.

By moving runtime PM handling out of uart_ops.pm, resume failures are no
longer silently ignored and all hardware accesses are guaranteed to
occur while the device is powered.

Signed-off-by: Praveen Talari <praveen.talari@oss.qualcomm.com>
---
 drivers/tty/serial/qcom_geni_serial.c | 37 +++++++++++++++++------------------
 1 file changed, 18 insertions(+), 19 deletions(-)

diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
index 7ead87b4eb65..e16a31b5dc32 100644
--- a/drivers/tty/serial/qcom_geni_serial.c
+++ b/drivers/tty/serial/qcom_geni_serial.c
@@ -1178,6 +1178,8 @@ static void qcom_geni_serial_shutdown(struct uart_port *uport)
 
 	qcom_geni_serial_cancel_tx_cmd(uport);
 	uart_port_unlock_irq(uport);
+
+	pm_runtime_put_sync(uport->dev);
 }
 
 static void qcom_geni_serial_flush_buffer(struct uart_port *uport)
@@ -1246,10 +1248,18 @@ static int qcom_geni_serial_startup(struct uart_port *uport)
 	int ret;
 	struct qcom_geni_serial_port *port = to_dev_port(uport);
 
+	ret = pm_runtime_resume_and_get(uport->dev);
+	if (ret < 0) {
+		dev_err(uport->dev, "Failed to resume and get %d\n", ret);
+		return ret;
+	}
+
 	if (!port->setup) {
 		ret = qcom_geni_serial_port_setup(uport);
-		if (ret)
+		if (ret) {
+			pm_runtime_put_sync(uport->dev);
 			return ret;
+		}
 	}
 
 	uart_port_lock_irq(uport);
@@ -1724,22 +1734,6 @@ static int geni_serial_resource_init(struct uart_port *uport)
 	return 0;
 }
 
-static void qcom_geni_serial_pm(struct uart_port *uport,
-		unsigned int new_state, unsigned int old_state)
-{
-
-	/* If we've never been called, treat it as off */
-	if (old_state == UART_PM_STATE_UNDEFINED)
-		old_state = UART_PM_STATE_OFF;
-
-	if (new_state == UART_PM_STATE_ON && old_state == UART_PM_STATE_OFF)
-		pm_runtime_resume_and_get(uport->dev);
-	else if (new_state == UART_PM_STATE_OFF &&
-		 old_state == UART_PM_STATE_ON)
-		pm_runtime_put_sync(uport->dev);
-
-}
-
 /**
  * qcom_geni_rs485_config - Configure RS485 settings for the UART port
  * @uport: Pointer to the UART port structure
@@ -1778,7 +1772,6 @@ static const struct uart_ops qcom_geni_console_pops = {
 	.poll_put_char	= qcom_geni_serial_poll_put_char,
 	.poll_init = qcom_geni_serial_poll_init,
 #endif
-	.pm = qcom_geni_serial_pm,
 };
 
 static const struct uart_ops qcom_geni_uart_pops = {
@@ -1795,7 +1788,6 @@ static const struct uart_ops qcom_geni_uart_pops = {
 	.type = qcom_geni_serial_get_type,
 	.set_mctrl = qcom_geni_serial_set_mctrl,
 	.get_mctrl = qcom_geni_serial_get_mctrl,
-	.pm = qcom_geni_serial_pm,
 };
 
 static int qcom_geni_serial_probe(struct platform_device *pdev)
@@ -1921,6 +1913,13 @@ static int qcom_geni_serial_probe(struct platform_device *pdev)
 
 	devm_pm_runtime_enable(port->se.dev);
 
+	PM_RUNTIME_ACQUIRE_IF_ENABLED(uport->dev, pm);
+	ret = PM_RUNTIME_ACQUIRE_ERR(&pm);
+	if (ret < 0) {
+		dev_err(uport->dev, "Failed to resume and get %d\n", ret);
+		goto error;
+	}
+
 	ret = uart_add_one_port(drv, uport);
 	if (ret)
 		goto error;

---
base-commit: b9810cd75b9fb56a3425d391cba3f608502bd474
change-id: 20260709-remove_uart_change_state-a1f7e783aeb0

Best regards,
--  
Praveen Talari <praveen.talari@oss.qualcomm.com>


^ permalink raw reply related	[flat|nested] 2+ messages in thread
end of thread, other threads:[~2026-07-10 16:11 UTC | newest]

Thread overview: 2+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-07-10  9:21 [PATCH] serial: qcom-geni: remove .pm callback, use runtime PM in startup/shutdown Praveen Talari
2026-07-10 16:10 ` kernel test robot

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox